JP6036072B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus that draws image data and displays it on a display such as a liquid crystal display using a line buffer having a storage capacity for one horizontal scan line.

  As is well known, display control of still images and moving images on a display device includes drawing processing for writing image data of still images and moving images into a buffer according to a drawing application, and display processing for reading out image data in the buffer and displaying it on the display device. This is realized by proceeding in parallel. As an image processing apparatus for performing such drawing processing and display processing, a frame buffer type image processing apparatus having a frame buffer for storing image data for one frame, and image data for one horizontal scan line are stored. There is a line buffer type image processing apparatus provided with a line buffer. Since the line buffer type image processing apparatus requires less storage capacity of the buffer to which the image data is written compared to the frame buffer type image processing apparatus, it is suitable for downsizing, and an on-vehicle image display system (for example It is suitable for construction of a system that requires space saving, such as a system that realizes meters such as a speedometer by image display). For example, Japanese Patent Application Laid-Open No. H10-228707 discloses a document related to a line buffer type image processing apparatus.

JP 2005-215252 A Japanese Patent Laid-Open No. 03-184182

  Conventionally, the display device is generally installed in such a manner that the vertical scanning direction is the vertical direction (vertical direction) and the horizontal scanning direction is the horizontal direction. However, in recent years, it has become increasingly common to install the display device by rotating it 90 degrees counterclockwise so that the vertical scanning direction is the left-right direction and the horizontal scanning direction is the up-down direction. For example, in the above-described in-vehicle image display system, it is necessary to install a display device on the driver's seat side of the dashboard. However, since the installation space is limited, it is often necessary to install the display device vertically. . Hereinafter, a display arranged so that the vertical scanning direction is the vertical direction (vertical direction) and the horizontal scanning direction is the left-right direction is referred to as a “horizontal display”, which is rotated 90 degrees counterclockwise. The installed display is called “vertical display”. A display installed by rotating the “horizontal display” 90 degrees clockwise may be referred to as a “vertical display”.

  The image displayed on the display unit is configured by combining a number of display elements such as symbols such as sprites, character strings, and lines. As shown in FIG. 6A, the display of the character string in the horizontal display is realized by displaying the fonts of the characters constituting the character string side by side in the horizontal scanning direction. On the other hand, when a character string is displayed on the vertical display, as shown in FIG. 6B, as a font for each character constituting the character string, in order to facilitate reading of the character string. It is necessary to display fonts obtained by rotating the one shown in FIG. 6A by 90 degrees clockwise (that is, fonts whose character height direction matches the horizontal scanning direction) side by side in the vertical scanning direction. Hereinafter, as shown in FIG. 6A, a character string formed by arranging fonts of constituent characters in the horizontal scanning direction is referred to as a “horizontal character string”. As shown in FIG. A character string formed by arranging the fonts in the vertical scanning direction is called a “vertical character string”. In the following, a font for configuring a horizontal character string is referred to as a “horizontal character string font”, and a font configuring a vertical character string is referred to as a “vertical character string font”.

  In the display of the horizontal character string, for example, as shown in FIG. 6C, a proportional font that can specify the display start position XS and the end position XE (position with the left end of the font image as the origin) for each character is used. It was possible to display the font image of each character so that the space between the characters is reduced by displaying the blank portion in an overlapping manner. However, a line buffer type image processing apparatus having a function for displaying a vertical character string has not been proposed so far, and a vertical character string cannot be displayed using a proportional font by using the line buffer type image processing apparatus. It was.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a technique that enables a line buffer image processing apparatus to display a vertical character string using a proportional font. .

  In order to solve the above problems, the present invention is a line buffer for storing image data representing an image for one scan line in a display, and attribute data indicating a display mode of a character string to be displayed on the display, Reading is instructed from a general-purpose table storing attribute data including information indicating the display start position and display end position of each character constituting the character string, and from a memory storing font data representing fonts of various characters. A memory interface that reads font data of a character, an image data generation unit that generates image data for one scan line using the font data read from the memory, and executes a drawing process to be written to the line buffer; In each horizontal scan period, the characters straddling the horizontal scan line are assigned to the attribute stored in the general-purpose table. A controller that identifies the character by referring to the data and instructs the image data generation unit to execute a drawing process for the corresponding character, and the character string is in the height direction of each character constituting the character string. Is a vertical character string in which the characters are aligned in the horizontal scanning direction and the characters are arranged in the vertical scanning direction, and the controller has a character across the horizontal scan line when the horizontal scan line straddles the vertical character string. And a parameter indicating how many lines of the character are crossed each time the horizontal scan line is updated, while the horizontal scan line crosses between the display start position and the display end position of the character indicated by the parameter. The character is determined as a display target, and the image data generation unit is instructed to execute a drawing process for the line indicated by the parameter. The image processing apparatus according to claim to provide.

  More specifically, when the vertical character string attribute data is stored in the general-purpose table, the controller sets the first and second parameters in a register or the like in association with the vertical character string. Here, the first parameter is a parameter indicating a character straddling the horizontal scan line when the horizontal scan line straddles the vertical character string corresponding to the first parameter. Is a parameter indicating which line of the character indicated by the first parameter the horizontal scan line is straddling. The initial value of the first parameter is a value indicating the first character of the vertical character string, and the initial value of the second parameter is a value indicating the first line of the first character. In the present invention, the first and second parameters are updated each time the horizontal scan line is updated, and the horizontal scan line straddles between the display start position and the display end position of the character indicated by the first parameter. In this case, the drawing process is executed for the line indicated by the second parameter (that is, the line where the horizontal scan line overlaps the character), and the display ends from the font display start position of each character constituting the vertical character string. The image data up to the position is drawn in the line buffer one line at a time starting from the first character. Thereby, the display of the vertical direction character string by a proportional font is implement | achieved. The initialization of the first and second parameters may be performed by the host CPU when writing the vertical direction character string attribute data to the general-purpose table, or when the image processing apparatus is initialized. You can go. Patent Document 2 describes a vertical writing layout of character strings, but does not disclose display control of vertical character strings in a vertical display device, and is a technique completely different from the present invention.

  In a more preferred aspect, the font data stored in the memory is compressed and encoded, and a decoding unit that decodes the font data read from the memory and supplies the decoded data to the image data generation unit is provided. And the controller instructs the decoding unit to decode the font data for the character determined to be displayed, and sets the attribute data to determine whether or not to decode the compressed encoded data for each character following the character. The decoding unit is instructed to decode the compression-encoded data for the character determined to require decoding. Specifically, among the characters following the character indicated by the first parameter, the controller displays the sum of the display widths of the characters between the character and the character indicated by the first parameter (that is, each of those characters). The value obtained by subtracting the display start position of the character from the display end position of the character indicated by the first parameter to the sum of the values obtained by subtracting the display start position from the display end position for It is not necessary to decode the compression-encoded data for characters after the character whose value obtained by subtracting the second parameter from the display end position is equal to or larger than the font size −1. judge. The details will be clarified in the description of the embodiment of the present invention (more precisely, the description of the operation example (B-2)). According to such an aspect, the font data stored in the memory is compressed. Even when a compression encoding method that has been encoded and requires a decoding result of a plurality of pixels preceding the pixel to be decoded is adopted, the image processing apparatus of the line buffer method, It is possible to display a vertical character string using a proportional font.

  In another preferred embodiment, the memory stores font data for vertical character strings representing fonts in which the height direction of characters is matched with the horizontal scanning direction, and attribute data of the vertical character strings. In this case, it is specified that the font data for the vertical direction character string is used for drawing the constituent characters. According to such an aspect, when each character constituting the vertical character string is displayed, the font for the horizontal character string is rotated 90 degrees clockwise and used in comparison with the aspect used. Thus, the amount of calculation processing is reduced, and it is possible to avoid a decrease in drawing performance and an increase in the scale of the calculation circuit.

It is a figure which shows the structural example of image display LSI100A of one Embodiment of this invention. It is a figure for demonstrating the attribute data of a vertical direction character string. It is a figure which shows the example of a display of a vertical direction character string in each when not using a proportional font and when using a proportional font. It is a figure for demonstrating operation | movement of image display LSI100A in the case of displaying a vertical direction character string, without using a proportional font. It is a figure for demonstrating operation | movement of 100 A of image display LSIs when displaying a vertical direction character string using a proportional font. It is a figure for demonstrating the display mode of the character string in a display.

(A: Configuration)
FIG. 1 is a block diagram showing a configuration of an image display system including an image display LSI (Large Scale Integrated circuit) 100A which is an embodiment of an image processing apparatus according to the present invention. In FIG. 1, in order to facilitate understanding of the function of the image display LSI 100A, a host CPU 201, an LCD (Liquid Crystal Display) 202, and a ROM 203 connected to the image display LSI 100A are shown together with the image display LSI 100A. Has been. The image display system shown in FIG. 1 is an in-vehicle system that is mounted on a vehicle such as a passenger car and displays character information representing an image such as a speedometer or traffic information, and the LCD 202 is provided on the driver seat side of the dashboard of the vehicle. It is placed vertically.

  The host CPU 201 is a processor that controls the image display system shown in FIG. An image for one frame displayed on the LCD 202 under the control of the host CPU 201 is configured by combining various image components such as symbol parts called sprites, character strings, and lines. The host CPU 201 supplies commands and data for displaying various image components on the LCD 202 to the image display LSI 100A. The ROM 203 stores compressed image data for various character fonts and various sprites constituting the character string, and compressed alpha data used for alpha blending. Although details will be described later, in the present embodiment, a plurality of pixels preceding the pixel to be decoded (for example, three pixels on the left, upper left, and immediately above in the case of a sprite) as compression encoding methods such as sprites and fonts. A compression encoding method that requires the decoding result is adopted.

  The image display LSI 100 </ b> A is a line buffer type image processing apparatus that displays an image on the LCD 202 in accordance with commands and data given from the host CPU 201. As shown in FIG. 1, the image display LSI 100A includes a CPU interface (indicated as “CPU I / F” in FIG. 1) 101, a color palette storage unit 102, a general-purpose table 103, a register 104, a controller 105A, ROM interface (denoted as “ROM I / F” in FIG. 1) 106, decoding unit 107, image data generation unit 108, image output unit 109, clock generation unit 110 that supplies an operation clock to these units, have.

  The CPU interface 101 is an interface that receives commands and data supplied from the host CPU 201 and supplies them to the related units in the image display LSI 100A. The color palette storage unit 102 is a circuit that stores color palette data representing a color palette when the image display LSI 100A is operated in the color palette mode. The color palette mode is an operation mode in which a color image is expressed by a predetermined number of colors (for example, 256 colors) out of 24 bit (or 16 bit) colors, for example, and the color palette data specifies those colors. It is data to be. The general-purpose table 103 serves as an attribute data storage unit that stores attribute data supplied from the host CPU 201 via the CPU interface 101. The register 104 is a circuit that stores various control data for sprite display and the like. In the present embodiment, the color palette storage unit 102, the general-purpose table 103, and the register 104 are provided separately, but these roles may be realized by assigning storage areas in one volatile memory.

  The attribute data stored in the general-purpose table 103 indicates the display mode of the sprites and character strings that constitute the image displayed on the LCD 202 in each vertical scanning period (in what position on the screen and in what form). It is data. The attribute data is supplied from the host CPU 201 for each vertical scanning period, and is stored in the general-purpose table 103 for each image component such as a sprite or a character string by the CPU interface 101.

  FIG. 2 is a diagram illustrating an example of storing character string attribute data in the general-purpose table 103. The attribute data of the character string includes data representing the display mode of the entire character string (such as the display position of the character string), data indicating each character constituting the character string, and the font type used for displaying each character. included. In FIG. 2, in the area where the addresses are LYSA to LYEA, the character string included in the image to be displayed on the LCD 202 is data indicating the display mode of the entire character string (each of layers # 0, # 1, and # 2 in FIG. 2). Are stored for several minutes.

  For example, layer # 0 shown in FIG. 2 is data indicating a display mode of the character string “ABCDE” shown in FIG. This layer # 0 includes the display position of the character string (the coordinates X and Y of the upper left corner of the character string whose origin is the upper left corner of the display area when the LCD 202 is placed horizontally). Further, in layer # 0 shown in FIG. 2, data (for example, character code) indicating each character (that is, each character of character number 0 to character number 4) constituting the character string in the general-purpose table 103 is stored. Font type attribute indicating the address (FCSA and FCEA) that defines the area, the type of font used to display each character, and the size of the character (number of pixels SZX in the horizontal scanning direction and number of pixels SZY in the vertical scanning direction) And the address (FTYP) of the area in which is stored. When a proportional font is used to display each character constituting the character string, the character display start position XS [n] and display end position XE [n] (n is the first character string in the font image). The data indicating the character number with the character as the 0th character) is stored in the area defined by the FCEA address from FCSA.

  As shown in FIG. 2, the ROM 203 stores compressed font image data in the order of character codes for various characters for each font type such as Gothic and Mincho. In the present embodiment, drawing processing for each character constituting the character string is realized by reading out and decoding the image data in the compression format of the font indicated by the font type attribute in the order of the character numbers.

  In the present embodiment, since the LCD 202 is placed vertically, all character strings displayed on the LCD 202 are vertical character strings. In this embodiment, three types of parameters such as a processing character number, a processing line number, and a display / non-display determination flag are associated with the character string in the register 104 in order to enable display of the vertical character string. Stored. Specifically, in the present embodiment, data (for example, layer # 0 in FIG. 2) that defines the display mode of the entire character string includes the addresses of the storage destinations of the three new parameters. Of course, the above three types of new parameters may be included in the data defining the display mode of the entire character string. In the present embodiment, the controller 105A determines whether or not the character string to be displayed is a vertical character string depending on whether or not these three types of parameters are stored in the register 104 in association with the character string attribute data. Can be made. The role of these three new parameters will be clarified in the operation example in order to avoid duplication. In this embodiment, in order to facilitate the display of the vertical character string, a compression format of the vertical character string font (that is, a character font arranged so that the height direction coincides with the horizontal scanning direction). Image data is stored in the ROM 203, and in the vertical character string attribute data, a value indicating the vertical character string font is set as the font type attribute.

  The controller 105A generates image data of various image constituent elements (that is, sprites, character strings, and lines) prior to display on the LCD 202 of the image data to be displayed in each vertical scanning period. Is a circuit for sequentially instructing. Specifically, the controller 105A creates an execution schedule of processing for generating image data of each image component based on the attribute data of each image component stored in the general-purpose table 103 in each vertical scanning period, In accordance with this execution schedule, an image data generation instruction for various image components is supplied to the image data generation unit 108. In the present embodiment, in addition to the introduction of the above-described three types of new parameters, the vertical character string display is realized by causing the controller 105 </ b> A to execute processing that significantly shows the features of the present embodiment. This point will be described in detail later.

  The image data generation unit 108 is a circuit that executes processing for generating image data of various image components one line at a time in order from the first line and writing them to the line buffer of the image output unit 109 in accordance with an image data generation instruction from the controller 105A. It is. As shown in FIG. 1, the image data generation unit 108 is connected to the ROM 203 via the decoding unit 107 and the ROM interface 106. The ROM interface 106 reads compressed image data (sprite data that is sprite image data or font data that is font image data) from the ROM 203 in accordance with an instruction given from the decoding unit 107, and outputs it to the decoding unit 107. To do.

  The decoding unit 107 reads the compressed sprite data or the compressed font data from the ROM 203 via the ROM interface 106 under the control of the controller 105A, and decodes the image for one line instructed by the controller 105A in units of pixels. And the decoding result is given to the image data generation unit 108. As shown in FIG. 1, the decoding unit 107 includes a pattern decoder 107A for decoding compressed sprite data and a font decoder 107B for decoding compressed font data. Although not shown in detail in FIG. 1, each of the pattern decoder 107A and the font decoder 107B has a first work memory for storing compressed data read from the ROM 203, and a predetermined number necessary for decoding subsequent pixels. And a second work memory for holding the pixel data of the compressed data stored in the first work memory while sequentially updating the storage contents of the second work memory. Decode with.

  The image data generation unit 108 receives image data for one line of each image component from the decoding unit 107, and stores the image data for each image component in a storage unit (not shown). The image data generation unit 108 includes a sprite rendering unit 108A, a font rendering unit 108B, and a line rendering unit 108C. The sprite rendering unit 108A reads the image data for one line of the sprite instructed to draw by the image data generation instruction from the storage unit, and edits (enlargement / reduction / deformation, color calculation) instructed by the image data generation instruction. Etc.) to write to the line buffer. The font rendering unit 108B reads image data for one line of the font instructed to be drawn by the image data generation instruction from the storage unit, and edits (enlargement / reduction / deformation, color calculation) instructed by the image data generation instruction. Etc.) to write to the line buffer. The line rendering unit 108C is a circuit that writes image data representing a line to the line buffer in accordance with an image data generation instruction.

The image output unit 109 includes line buffers 109A and 109B each having a capacity capable of storing image data for one horizontal scan line. Of these line buffers 109A and 109B, one is a write line buffer and the other is a read line buffer. The line buffer for reading is the one that has been the write line buffer up to that time in synchronization with the horizontal synchronizing signal of the LCD 202. A line buffer is used as a write line buffer. In each horizontal scanning period, one line of image data stored in the readout line buffer is read and supplied to the LCD 202 for display, while one line of image data displayed after one horizontal scanning period is displayed. The image data generation unit 108 writes the data in the writing buffer.
The above is the configuration of the image display LSI 100A.

(B: Operation)
Next, the operation of the image display LSI 100A will be described. In the following, in order to clarify the role of the three newly introduced parameters (processing character number, processing line number, and display / non-display flag), first, display the vertical character string without using a proportional font. The case where it performs is demonstrated. When the proportional font is not used, the vertical character string is displayed in the vertical scanning direction so that the vertical character string font images of the characters do not overlap with each other as shown in FIG. This is realized by arranging and displaying in one row without any gaps.

(B-1: Operation when displaying a vertical character string without using a proportional font)
As described above, in the general-purpose table 103 of the image display LSI 100A, the host CPU 201 writes attribute data for sprites, character strings, and the like constituting an image displayed on the LCD 202 in each vertical scanning period. . As described above, in this embodiment, all character strings are vertical character strings. However, in this operation example, the character string attribute data written in the general-purpose table 103 does not include information indicating the display start position and display end position of each character. This is because in this operation example, a vertical character string is displayed without using a proportional font.

  For each horizontal scanning period, the controller 105A determines whether or not the horizontal scanning line in the next horizontal scanning period straddles each image constituent element corresponding to the attribute data (that is, whether to be a display target in the next horizontal scanning period). The image data generation instruction for the image component determined to be a display target is generated for each image component and given to the image data generation unit 108.

Here, if the determination target of whether or not to be a display target in the next horizontal scanning period is a horizontal character string (see FIG. 6A), the vertical scanning direction indicated by the attribute data of the horizontal character string. When the display position Y, the size SZY of the horizontal character string in the vertical scanning direction, and the position VD of the horizontal scan line drawn in the next horizontal scanning period satisfy the relationship of the following expression (1), the controller 105A The horizontal character string is determined as a display target (the same applies when determining whether a sprite is a display target).
Y ≦ VD ≦ Y + SZY (1)

  On the other hand, in the case of a vertical character string, it is possible to determine whether or not the first character is a display target using the above formula (1). (1) cannot be used to determine whether or not the display target. This is because data indicating the display position of each of the second and subsequent characters is attribute data in order to determine whether the second and subsequent characters of the vertical character string are to be displayed / hidden by the above formula (1). This is because such data is not included in the attribute data of the character string. Also, the vertical scanning direction display position of the character to be determined is added to the vertical scanning direction display position of the entire vertical character string by adding the size of all characters preceding the determination target character in the vertical scanning direction. Although it is not impossible to calculate the display position, the calculation of the display position for each character after the second character causes problems such as a decrease in drawing performance and an increase in the scale of the arithmetic circuit. .

  Therefore, in this embodiment, as described above, by introducing three new parameters of the processing character number, the processing line number, and the display / non-display determination flag, the drawing performance is reduced and the scale of the arithmetic circuit is increased. It is possible to display a vertical character string on a line buffer image processing apparatus without causing a problem. Here, the display / non-display determination flag indicates whether or not the horizontal scan line in the next horizontal scanning period straddles the vertical character string corresponding to the display / non-display determination flag (that is, the vertical character string). Is a parameter indicating whether or not to be a display target in the next horizontal scanning period). The processing character number is a parameter indicating a character straddling the horizontal scan line when the vertical character string straddles the horizontal scan line in the next horizontal scanning period. The processing line number is a parameter indicating how many lines of the font image of the character indicated by the processing character number overlap with the horizontal scan line. Hereinafter, display control of the vertical character string using these three types of parameters will be described.

  In the present embodiment, the above three types of parameters are all reset to 0 when the image display LSI 100A is initialized. Note that when writing attribute data for a character string, the host CPU 201 or the controller 105A may set 0 as an initial value for the above three types of parameters.

  First, the controller 105A performs the calculation shown in the above equation (1) as in the case of the horizontal character string, and determines whether to display / hide the first character of the vertical character string. That is, the controller 105A determines that no display is performed until the position VD of the horizontal scan line to be drawn in the next horizontal scan period reaches the display position Y included in the layer # 0 of the attribute data of the vertical character string. The three types of parameters are not updated. When the position VD of the horizontal scan line to be drawn in the next horizontal scanning period reaches the display position Y included in the layer # 0 of the attribute data of the vertical character string (that is, when VD = Y), the controller 105A starts updating the three types of parameters.

  More specifically, when the horizontal scan line position VD reaches the display position Y included in the layer # 0 of the vertical character string attribute data, the controller 105A sets the display / non-display determination flag to 1 (that is, Each time the horizontal scan line is updated (that is, the position VD of the horizontal scan line is incremented by 1) until the display / non-display determination flag is reset to 0. Every time, the following first and second processes are executed. The first process refers to the processing character number and processing line number at that time, and instructs the image data generation unit 108 to draw a line indicated by the processing line number of the character indicated by the processing character number. is there. In the second process, when the process line number indicates the last line of the character (specifically, when process line number = SZX-1), the process character number is incremented to indicate a subsequent character. And the processing line number is updated to a value indicating the first line of the subsequent character (that is, 0). Conversely, if the processing line number does not indicate the last line, the processing line number is incremented. And updating to a value indicating the next line. Thereafter, the controller 105A displays a non-display flag when the processing character number indicates the last character of the vertical character string and the processing line number becomes a value indicating the last line of the font image of the character. Is reset to 0.

  For example, for the vertical character string shown in FIG. 3A, when (7, 7) is set as the display position (X, Y) and SZX = SZY = 32 is set as the character size, In the process of updating the horizontal scan line position VD to 0, 1, 2,..., The three types of parameters are updated as shown in FIG. As shown in FIG. 4, during VD = 7 to 166, the display / non-display determination flag for the vertical character string is set to 1, and the drawing process for the vertical character string is performed. Specifically, since the processing character number = 0 during the period of VD = 7 to 38, drawing processing is performed for the first character (that is, “A”) of the vertical character string, and VD = 38. In this case, since the processing line number is “31” indicating the last line of the character, the processing character number is incremented to “1” and the processing line number is set to “0” when the horizontal scan line is updated. Similarly, since the processing character number = 1 in the period of VD = 39 to 70, the drawing process for the second character (ie, “B”) of the vertical character string is performed, and so on. Since the processing character number = 4 during the period of VD = 135 to 166, the drawing process is performed for the fifth character (that is, “E”) of the vertical character string. Then, as a result of performing the display process described above subsequent to the drawing process, the vertical character string “ABCDE” is displayed on the LCD 202.

  As described above, according to the present embodiment, it is possible to determine whether or not the current processing line is a display target without adding the vertical sizes of all the characters preceding the determination target character. Therefore, it is possible to cause an image processing apparatus that draws image data and displays it on a display using a line buffer having a storage capacity for one line to display a vertical character string without using a proportional font. become.

(B-2: Operation when displaying a vertical character string using a proportional font)
Next, the operation of the image display LSI 100A when a vertical character string is displayed using a proportional font will be described. When the proportional font is used, the vertical character string is displayed according to the display start position XS [n] and the display end position XE [n] of each character included in the attribute data, as shown in FIG. In the font image for the vertical character string of the character, the position indicated by the display end position XE [n] and the next character (that is, the character number = n + 1 for the character font of the character number = n) so that the blank portions overlap each other. Are displayed side by side in the vertical scanning direction so that the positions indicated by the display start position XS [n + 1] match.

Also in this operation example, the controller 105A executes the first and second processes described above every time the position VD of the horizontal scan line to be displayed is updated in the next horizontal scanning period. However, the first and second processes in the case of performing a vertical character string using a proportional font differ from the processes in the case of not using a proportional font in the following points. That is, in the first process, when the process character number = m, the controller 105A performs the process of the font image of the character with the process character number = m only when the process line number satisfies the following expression (2). The image data generation unit 108 is instructed to execute drawing processing for the line indicated by the line number.
XS [m] ≦ processing line number ≦ XE [m] (2)

  In the second process, when the process character number = m, the controller 105A increments the process character number to indicate a subsequent character when the process line number is the display end position XE [m] of the character. The value is updated to the value (ie, m + 1) and the processing line number is reset to the display start position of the subsequent character (ie, XS [m + 1]).

  Further, in the first processing when the proportional font is not used, the controller 105A decodes the compressed font data for each character constituting the vertical character string one character at a time in the display order, but uses the proportional font. In some cases, it may be necessary to decode a plurality of types of compressed font data in each horizontal scanning period. More specifically, in the first process in the case of using a proportional font, the controller 105A instructs the image data generation unit 108 to execute the drawing process for the character indicated by the process character number. It is determined whether or not it is necessary to decode the compressed font data for each subsequent character, and the decoding unit 107 is instructed to decode the compressed font data for the character determined to be decoded. The reason why it may be necessary to decode a plurality of types of compressed font data within the horizontal scanning period when displaying a vertical character string using a proportional font is as follows.

  For example, when the vertical character string “ICFID” shown in FIG. 5A is displayed on the LCD 202, the first character of the vertical character string (that is, character number = 0, in the example shown in FIG. 5A). The first character “I”) may be displayed on the LCD 202 only when XS [0] ≦ processing line number ≦ XE [0]. Therefore, it is sufficient to specify the line corresponding to XS [0] in response to the processing line number = XS [0] and to start decoding the compressed font data for the character, and the processing line number = XE [ 0] and the compressed font data for the character with character number = 1 by designating the line corresponding to XS [1] when the processing character number is incremented and the processing line number is reset in the second processing. Looks like it should start decoding.

  However, in this embodiment, as a compression encoding method for font data, when decoding, a predetermined number of pixels preceding the pixel to be decoded are decoded, and the compression code required for decoding the pixel to be decoded Is adopted. That is, the compressed font data can be decoded only from the first line. For this reason, it is impossible to decode the compressed font data for the character of character number = 1 from the middle of the data. That is, in order to perform the line drawing process corresponding to XS [1] for the character with character number = 1 in the next horizontal scanning period triggered by the increment of the process character number and the reset of the process line number. Therefore, it is necessary to decode the portion preceding the line (that is, the blank portion) of the compressed font data corresponding to the character in advance. For example, when the horizontal scan line is FLIN1 shown in FIG. 5A, the compressed font data is decoded for each character of character numbers = 0 and 1, and the horizontal scan line is shown in FIG. In the case of FLIN2, the compressed font data is decoded for each character of character numbers = 1 and 3. This is the reason why it is necessary to decode a plurality of types of compressed font data within a horizontal scanning period when a vertical character string is displayed using a proportional font.

As described above, in this embodiment, since it may be necessary to decode a plurality of types of compressed font data within the horizontal scanning period, the controller 105 </ b> A determines the compressed font for each character following the character indicated by the processing character number. It is determined whether or not data decoding is necessary (in other words, whether or not there is a character across the horizontal scan line in the blank portion of the font). Specifically, when the processing character number = m, the controller 105A performs the calculations shown in the following equations (3) to (5) for each character of the character number = m + k (k = 1, 2,...). The index value Dist3 “m + k” is calculated to determine that it is necessary to decode the compressed font data for characters whose index value Dist3 “m + k” is smaller than SZX-1, and the decoding unit 107 is instructed to perform the decoding. To do.
Dist1 [m + k] = XE [m] −XS [m + k] (3)
Dist2 [m + k] = processing line number−Dist1 [m + k] (4)
Dist3 [m + k] = XE [m + k] −Dist2 [m + k] + F [m + k] (5)
However, F [m + k] is the sum of the display widths of the characters between the character number = m and the character number = m + k (that is, zero when k = 1, j = 1 when k ≧ 2) (XE [m + j] −XS [m + j]) from k to k−1).

  As shown in FIG. 5B, when k = 1, Dist1 [m + 1] calculated according to the equation (3) is the character of character number = m (in the example shown in FIG. 5B, the character “ I ″) represents the distance between the display end position of the font image and the display start position of the font image of character number = m + 1 (in the example shown in FIG. 5B, character “B”). Dist2 [m + 1] calculated according to (4) is the number of lines in the font image of the character whose character number = m + 1 is the line indicated by the processing line number (in other words, the horizontal scan line) for the character whose character number = m. Shows whether it overlaps the eyes.

  It is clear if Dist1 [m + 1] calculated according to equation (3) is substituted into the right side of equation (4), and Dist2 [m + 1] calculated according to equation (4) is substituted into the right side of equation (5). As shown in FIG. 5B, Dist3 [m + 1] represents the distance between the position of the horizontal scan line and the display end position of the font of the character of character number = m + 1. Therefore, if the value of Dist3 [m + 1] is SZX-1 or more, the horizontal scan line in the next horizontal scanning period does not straddle the blank portion of the font image after the character of character number = m + 1, and after the character. There is no need to decode the compressed font data. Similarly, when k ≧ 2, Dist3 [m + k] represents the distance between the display end position of the font of the character number = m + k and the horizontal scan line, and the value of Dist3 [m + k] is greater than or equal to SZX-1. For example, the horizontal scan line in the next horizontal scanning period does not straddle the blank portion of the font image after the character of character number = m + k, and it is not necessary to decode the compressed font data for the character and the subsequent characters. This is the reason why it is possible to determine whether or not it is necessary to decode the compressed font data for characters after the character number = m + k by comparing the index value Dist3 [m + k] with SZX-1.

  Further, in this embodiment, it is not determined whether or not the compressed font data needs to be decoded only for the character immediately after the character indicated by the processing character number, but the processing character number is kept until the value of the instruction value Dist3 becomes SZX-1 or more. It is determined whether or not it is necessary to decode the compressed font data for the character subsequent to the character indicated by. Depending on the configuration of the vertical character string to be displayed, the character indicated by the processing character number (in the example shown in FIG. 5A, “C”), as in the case where the horizontal scan line is FLIN2 in FIG. ) Immediately after the character (“f” in the example shown in FIG. 5A), even if it is not necessary to decode the compressed font data, the next character (in the example shown in FIG. 5A, 2 This is because it may be necessary to decode the compressed font data for the character “I”).

  As described above, according to the present embodiment, by causing the controller 105A to execute the first and second processes, a vertical character string can be displayed using a proportional font. As described above, according to the present embodiment, it is possible to cause a line buffer image processing apparatus to display a vertical character string using a proportional font.

(C: deformation)
Although the embodiment of the present invention has been described above, it goes without saying that the following modifications may be added to this embodiment.
(1) In the above embodiment, in addition to the compressed font data of the font for the horizontal character string, the compressed font data of the font for the vertical character string is stored in the ROM 203 in advance, and when the vertical character string is displayed. The latter was used for. However, the ROM 203 stores only the compressed font data of the font for the horizontal character string, and when displaying the vertical character string, the entire compressed font data for the horizontal character string is decoded, and the decoding result Alternatively, the image data of the font represented by may be rotated 90 degrees clockwise. The ROM 203 stores only compressed font data for the vertical direction character string, and when displaying the horizontal direction character string, the entire compressed font data for the vertical direction character string is decoded and the decoding result is represented. The font image data may be used after being rotated counterclockwise by 90 degrees.

(2) In the above embodiment, a method of referring to the decoding result of several preceding pixels is adopted as a compression encoding method of sprite data and font data stored in the ROM 203, but other methods are adopted. Is of course good. Of course, sprite data and font data not subjected to compression encoding in the ROM 203 may be mixed with those subjected to compression encoding. Needless to say, when the ROM 203 stores only uncompressed sprite data and font data, the decoding unit 107 may be omitted.

(3) In the above embodiment, the case where a character string is always displayed as a vertical character string has been described. However, whether the character string is a vertical character string or a horizontal character string in the attribute data of the character string. It is also possible to include a flag indicating whether or not the controller 105A performs display control of the vertical character string (or display control of the horizontal character string) according to the flag.

(4) In the above embodiment, the attribute data includes information indicating the display start position and the display end position of each character only when the vertical character string is displayed using the proportional font. However, regardless of whether a proportional font is used or not, information indicating the display start position and display end position of each character is always included in the attribute data, and when no proportional font is used, display starts for all characters. Position = 0 and display end position = SZX-1 may be set, and the controller 105A may always execute the processing described in (B-2). In this case, Dist3 [m + k] calculated according to the equation (5) is “(2+ (k−1)) × (SZX−1) −processing line number”. Here, since the processing line numbers for all characters are 0 ≦ processing line number ≦ SZX−1, Dist3 [m + k] is always greater than or equal to SZX−1 for all characters. For this reason, in the first process in (B-2), the compressed font data is not decoded for the character of character number = m + k. In the second processing in (B-2), when the processing character number = XE [m] (= SZX-1), the processing character number and the processing line number are reset, and the processing line number is It is reset to XS [m + 1] (= 0). That is, if the display start position and the display end position are set as described above, the processing contents of the first and second processes in (B-2) are completely the same as the processing contents of each process in (B-1). Matches. As described above, according to the present modification, it is possible to perform the display control of the vertical direction character string uniformly regardless of whether or not the proportional font is used.

(5) Although the application example of the present invention to the vehicle-mounted image display system has been described in the above embodiment, for example, an image display system incorporated in a so-called information home appliance such as a refrigerator, a washing machine, and a rice cooker having a display. Of course, the present invention may be applied. Even in this type of information home appliances, the space for installing the image display system and the installation space for the display cannot be sufficiently taken, and it is often necessary to install the display vertically or use a line buffer system. In addition, the display frequency of the character information is considered to be extremely high. For the same reason, it is conceivable to apply the present invention to an image display system of a portable information terminal such as a mobile phone, a portable game machine, or a PDA.

(6) In the above-described embodiment, an example of application to display control of a vertical character string using a proportional font has been described. However, it can also be used for kerning (adjustment of character spacing) of a vertical character string. In each of the above embodiments, the case where all the character strings to be displayed are vertical character strings has been described, but it is of course possible that both vertical character strings and horizontal character strings are mixed.

DESCRIPTION OF SYMBOLS 100A ... Image display LSI, 101 ... CPU interface, 102 ... Color palette memory | storage part, 103 ... General purpose table, 104 ... Register, 105A ... Controller, 106 ... ROM interface, 107 ... Decoding part, 107A ... Pattern decoder, 107B ... Font decoder , 108: Image data generation unit, 108A ... Sprite rendering unit, 108B ... Font rendering unit, 108C ... Line rendering unit, 109A, 109B ... Line buffer, 109 ... Image output unit, 110 ... Clock generation unit, 201 ... Host CPU, 202 ... LCD, 203 ... ROM.

Claims (5)

In an image processing apparatus for drawing a character string in which characters are continuously arranged in a direction perpendicular to a horizontal scan line,
A line buffer for storing image data representing an image for one horizontal scan line;
An image data generation unit that generates image data for one horizontal scan line using font data acquired based on attribute data indicating a display mode of the character string, and executes drawing processing to be written in the line buffer;
A controller that specifies a character across a horizontal scan line in each horizontal scanning period with reference to the attribute data indicating a display mode of the character string, and instructs the image data generation unit to execute a drawing process on the corresponding character When,
Comprising
The attribute data includes a display / non-display flag, a processed character number, and a processed line number as parameters for the character string, and includes a display start position and a display as parameters for each character constituting the character string. Including information indicating the end position,
The display / non-display flag is a parameter indicating whether or not the character string is a display target,
The processing character number is a parameter indicating a character across the horizontal scan line when a horizontal scan line straddles the character string,
The processing line number is a parameter indicating which line of the character indicated by the processing character number the horizontal scan line crosses,
The controller is
When a horizontal scan line straddles the character string, the character string is determined as a display target and a value indicating display is set in the display / non-display flag,
When the display / non-display flag is a value indicating display, the processing line number is updated while updating the processing line number every time the horizontal scan line is updated with the character indicated by the processing character number as a drawing target. It is determined whether the line indicated by is a line between the display start position and the display end position of the character to be drawn,
An image processing apparatus that instructs the image data generation unit to execute a drawing process for a line indicated by the processing line number when it is determined that the line is between a display start position and a display end position . The font data is subjected to compression encoding,
  A decoding unit that decodes the font data acquired based on the attribute data and gives the image data generation unit;
  The controller is
  The decoding unit is instructed to decode the font data for the character that is determined to be displayed, and the necessity of decoding the font data for each character that follows the character is determined based on the attribute data. Then, the decoding unit is instructed to decode the font data for the determined character.
  The image processing apparatus according to claim 1.   The controller displays the character indicated by the processed character number in the sum of the display widths of the characters between the character indicated by the processed character number and the character indicated by the processed character number. A value obtained by adding a value obtained by subtracting the display start position of the character from the end position and a value obtained by subtracting the number of lines indicated by the processing line number from the display end position of the character. Determining that font data decoding is unnecessary for characters after the font size minus 1
  The image processing apparatus according to claim 2. The said image data generation part uses the font data for the vertical direction character string used for the drawing of the character string which has arrange | positioned the character continuously in the direction perpendicular | vertical to a horizontal scan line as said font data. The image processing apparatus according to any one of 1 to 3. When displaying the character string without using a proportional font, a value representing the entire image represented by font data is set in the information indicating the display start position and the display end position. 5. The image processing apparatus according to 4.

Images