JP5139779B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming technique for generating raster data having a predetermined number of colors based on vector data.

  In general, a display attached to an embedded device or the like often has a limited number of colors that can be displayed. The reason can be roughly divided into the following two.

  One is when the number of colors that the display itself can represent as hardware is limited. The other is the case where the palette limits the number of colors that can be displayed at one time in order to speed up the processing.

  When displaying raster data having the number of colors exceeding the number of colors on the display in which the number of colors that can be displayed is limited in this way, the image forming apparatus needs to perform color reduction processing on the raster data. It becomes.

  As a typical representative color reduction process, for example, among colors constituting raster data, a color having a large area in the raster data (a color having a large number of pixels) is preferentially left, and a color having a small area (a number of pixels) For example, a color reduction process of converting a small number of colors) to another color.

Alternatively, a color reduction process in which the user specifies a color to be displayed as a palette and converts the other colors into any of the colors specified as the palette by the user is given.
JP 2003-87578 A

  Here, consider the case where the data displayed on the display is given as vector data described in the page description language, and the number of colors that can be displayed on the display is limited. In this case, it is necessary to extract color information that can be expressed by vector data described in the page description language and generate a palette, but in the case of vector data, all color information that can be expressed is explicitly described. It has not been done. For example, processing details (elements) may be described, such as “anti-aliasing” or “translucent color overlay (α blending)”, and the corresponding specific color information itself may not be described. It is. Such color information is extracted for the first time by calculation by anti-aliasing or as a result of α blending processing, and is not described in the vector data from the beginning.

  For this reason, it is difficult to generate a palette for color reduction processing directly based on vector data.

  On the other hand, after generating raster data based on the description of vector data, a palette is generated based on the color information constituting the raster data, and color reduction processing (for example, color reduction processing for colors with a small area) is performed using this palette. ). However, in this case, a situation may occur in which the color information explicitly described in the vector data is not extracted and is not included in the palette. In this case, for example, the color intended by the designer of the vector data is not reflected in the display result, resulting in low-quality color reduction processing.

  The present invention has been made in view of the above problems, and an object of the present invention is to realize high-quality color reduction processing using a palette when generating raster data having a predetermined number of colors based on vector data. .

In order to achieve the above object, an image forming apparatus according to the present invention has the following configuration. That is,
An image forming apparatus that generates raster data having a predetermined number of colors based on vector data described in a page description language,
Data generating means for generating raster data using all color information that can be expressed by the vector data;
Extraction means for extracting color information explicitly described in the elements described in the vector data;
Pallet generation for generating the palette with the predetermined number of colors using the color information extracted by the extraction unit and a part of the color information used for generating the raster data in the data generation unit Means,
A color conversion table for allocating color information not used for generating the palette among the color information used for generating the raster data in the data generating means to any color information constituting the palette Table generating means for generating
A color reduction processing unit configured to perform a color reduction process on the raster data generated by the data generation unit using the palette and the color conversion table.

  According to the present invention, it is possible to realize high-quality color reduction processing using a pallet when generating raster data having a predetermined number of colors based on vector data.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

1. Hardware Configuration of Image Forming Apparatus FIG. 1 is a diagram showing a configuration of an image forming apparatus 101 according to an embodiment of the present invention. In the figure, a CPU 108 controls the entire image forming apparatus 101.

  The ROM 102 stores a control program and various fixed data for realizing the image forming method according to the present embodiment processed by the CPU 108. The RAM 103 is configured by SRAM, DRAM, and the like, and stores program control variables and the like. Various setting parameters and various work buffers are also stored in the RAM 103.

  The external storage unit 104 includes a hard disk and stores files such as documents and images.

  The input unit 105 includes a keyboard and a touch panel, and the operator performs various input operations via the input unit 105. The display unit 106 includes a cathode ray tube, an LCD, an LED, and the like and plays a role of notifying the operator of the processing result.

  The I / F 107 is an interface for connecting to a network (not shown). Examples of connection methods include LAN and USB.

2. Example of Vector Data to be Processed by Image Forming Apparatus FIG. 2 is a diagram illustrating an example of vector data described by a page description language to be processed by the image forming apparatus 101. In the present embodiment, it is assumed that the vector data to be processed is an XML file in which graphics are described in the SVG format. SVG is an abbreviation for Scalable Vector Graphics. XML is an abbreviation for Extensible Markup Language. Details of SVG can be found at, for example, http: // www. w3. org / Graphics / SVG /.

  In general, in SVG, a color is designated by “attribute”, “element”, and “CSS” (Cascading Style Sheets).

  The “attribute” is an explicit description of the displayed color. As the “attribute”, a fill attribute that specifies the color inside the figure, a fill-opacity attribute that specifies the opacity thereof, a stroke attribute that specifies the color of the outline of the figure, and a stroke-opacity attribute that specifies the opacity thereof Etc.

  In the example of FIG. 2, fill = “# ff0000” (202) is specified as the color inside <circle> (201), and fill-opacity = “0.5” (203) is specified as the opacity thereof. These colors are “# 7fff0000” when expressed in 32-bit ARGB.

  “Element” describes processing contents. Examples of the “element” include a <linearGradient> element that specifies how to apply gradation, a <radialGradient> element, a <pattern> element that specifies a pattern, a <filter> element that specifies a filter, and the like.

  “CSS” is defined in the CSS specification (http://www.w3.org/Style/CSS/), and the description thereof is omitted here.

  2 is displayed on the display unit 106, the result is as shown in FIG.

3. Functional Configuration of Image Forming Apparatus FIG. 4 is a block diagram showing a functional configuration of the image forming apparatus 101 according to the embodiment of the present invention. Here, it is assumed that the display unit (CRT) 413 constituting the image forming apparatus 101 according to the present embodiment has a capability of outputting a color with 32-bit ARGB per pixel. However, only 16 colors can be registered in the palette due to the limitation of the image forming apparatus 101. As a result, the colors that can be displayed on the cathode ray tube 413 at the same time are limited to the 16 colors registered in the palette. It has become.

  In the figure, a vector data storage unit 402 stores vector data displayed on the cathode ray tube 413. As described above, in the present embodiment, the vector data stored in the vector data storage unit 402 is an XML file in which a figure is described in the SVG (http://www.w3.org/Graphics/SVG/) format. Yes (see FIG. 2).

  The vector data analysis unit 403 reads the vector data stored in the vector data storage unit 402 and extracts color information explicitly described in the vector data. The vector data color information storage unit 404 stores the color information extracted by the vector data analysis unit 403.

  The non-reduced color raster data generation unit 401 reads the vector data stored in the vector data storage unit 402, and generates raster data using all colors that can be expressed by the vector data. Specifically, raster data expressed in 32-bit ARGB per pixel is generated according to the SVG specification. Hereinafter, such raster data is referred to as “non-reduced color raster data”.

  The non-reduced color raster data storage unit 414 stores the non-reduced color raster data generated by the non-reduced color raster data generation unit 401.

  The raster data analysis unit 407 reads the non-reduction color raster data stored in the non-reduction color raster data storage unit 414, and counts the number of pixels of each color constituting the non-reduction color raster data.

  The raster data color information storage unit 408 stores the number of pixels of each color counted by the raster data analysis unit 407 in association with the color information of each color.

  A color reduction palette generation unit 405 is a palette in which color information for the number of colors that can be displayed on the cathode ray tube 413 is defined based on the color information stored in the vector data color information storage unit 404 and the raster data color information storage unit 408. (Referred to as “color reduction palette”).

  The reduced color palette storage unit 406 stores the reduced color palette generated by the reduced color palette generation unit 405.

  The color conversion table generation unit 409 converts color information that is not included in the color reduction palette among the color information stored in the raster data color information storage unit 408 into any color information included in the color reduction palette. Generate a color conversion table.

  The color conversion table storage unit 410 stores the color conversion table generated by the color conversion table generation unit 409.

  The color reduction processing unit 411 uses the color reduction palette stored in the color reduction palette storage unit 406 and the color conversion table stored in the color conversion table storage unit 410 to perform non-color reduction stored in the non-color reduction raster data storage unit 414. Apply color reduction processing to raster data. The raster data obtained as a result of the color reduction processing in the color reduction processing unit 411 is hereinafter referred to as “color reduction raster data”.

  The display control unit 412 performs display control for displaying the color reduction raster data generated in the color reduction processing unit 411 on the cathode ray tube 413.

  The functional configuration shown in the figure shows an embodiment of the image forming apparatus of the present invention. Depending on the apparatus, a scanner unit, a printer unit, a modem, a speaker, and the like are provided in addition to the above configuration. May be. Further, when the image forming method according to the present invention is realized by software or the like, each block in the figure does not necessarily have to be arranged in the image forming apparatus.

4). Process Flow in Image Forming Apparatus Hereinafter, the process flow in the image forming apparatus 101 will be described with reference to the flowchart of FIG. The description will be made with reference to FIGS. 6 to 8 showing the color reduction palette generated by the color reduction palette generation unit 405 and FIG. 9 showing the color conversion table generated by the color conversion table generation unit 409. .

  In step S501, the non-reduced color raster data generation unit 401 reads vector data (SVG) from the vector data storage unit 402, and generates non-reduced color raster data (32-bit bitmap data). In this embodiment, anti-aliasing is performed in four stages, and white transparent is used as the background color. The generated non-reduced color raster data is as shown in FIG. 3, and it is assumed that the number of colors constituting the non-reduced color raster data is 30.

  In step S502, the vector data analysis unit 403 reads the vector data (SVG) from the vector data storage unit 402, analyzes it, and extracts color information explicitly described in the elements of the SVG. These are explicitly given at the time of SVG creation, for example, the colors intended as output by the designer of vector data.

  In step S503, the vector data analysis unit 403 determines whether or not the number of colors of the extracted color information exceeds the number of colors that can be displayed by the CRT 413 (in this embodiment, “16”).

  If it is determined in step S503 that the number has been exceeded, the process ends. On the other hand, if it is determined that it does not exceed, the process proceeds to step S504, and the extracted color information is stored in the vector data color information storage unit 404.

  In step S505, the color reduction palette generation unit 405 reads the color information stored in the vector data color information storage unit 404 and adds it to the color reduction palette. For example, in the case of the vector data shown in FIG. 2, fill = “# ff0000” is explicitly described as the color information inside <circle>, and fill-opacity = “0.5” is explicitly described as the opacity thereof. . Since these are expressed as 32-bit ARGB and become “# 7fff0000”, they are added to the color reduction palette. FIG. 6 shows a subtractive color palette generated based on the vector data shown in FIG. The generated color reduction palette is stored in the color reduction palette storage unit 406.

  In step S506, the reduced color palette generation unit 405 reads the reduced color palette from the reduced color palette storage unit 406, and determines whether all the color information for 16 colors has been registered.

  If it is determined in step S506 that all the color information for 16 colors has been registered, the process proceeds to step S508. Here, the color-reduction palette is in the state shown in FIG. 6, and color information is not registered for palette numbers 3 to 15. For this reason, in step S506, it is determined that the color-reduction palette still has space, and the process proceeds to step S507.

  In step S507, color information is registered in the color reduction palette based on the non-color reduction raster data stored in the non-color reduction raster data storage unit 414. Specifically, the raster data analysis unit 407 reads the non-reduction color raster data from the non-reduction color raster data storage unit 414, counts the number of pixels of each color constituting the non-reduction color raster data, and associates it with the color information of each color. The raster data is stored in the color information storage unit 408. Further, the color reduction palette generation unit 405 reads the color information stored in the raster data color information storage unit 408, sorts color information other than the color information already included in the color reduction palette based on the number of pixels, and has a large number of pixels. Sequentially add color information to the color reduction palette. As a result, all the color information for 16 colors is registered in the color reduction palette as shown in FIG. The reduced color palette after the addition is stored in the reduced color palette storage unit 406.

  In step S <b> 508, the color conversion table generation unit 409 reads the reduced color palette stored in the reduced color palette storage unit 406. Then, a color conversion table (FIG. 8) is generated so that the color information included in the subtractive color palette is directly converted into the palette number, and is stored in the color conversion table storage unit 410.

  In step S509, the color conversion table generation unit 409 reads the color conversion table from the color conversion table storage unit 410 and the color information from the raster data color information storage unit 408, respectively. Then, it is determined whether there is color information that is not included in the color conversion table among the color information read from the raster data color information storage unit 408.

  If it is determined in step S509 that it does not exist, the process proceeds to step S512. In the case of this embodiment, the number of colors of color information read from the raster data color information storage unit 408 is 30, and there is color information that is not included in the subtractive color palette, so that it is added to the color conversion table.

  In step S510, the color conversion table generation unit 409 calculates the similarity between the color information not included in the color conversion table and the 16-color color information registered in the color reduction palette.

  In step S511, a color conversion table is generated so that it is converted into the palette number having the highest similarity as a result of the calculation in step S510. As a result, the color conversion table is as shown in FIG. The color conversion table generated in this way is stored in the color conversion table storage unit 410.

  In step S512, the color reduction processing unit 411 reads the color conversion table from the color conversion table storage unit 410 and the non-color reduction raster data from the non-color reduction raster data storage unit 414, respectively. Convert according to

  As a result, the non-reduced color raster data is converted into a 4-bit palette image (reduced color raster data) and transmitted to the display control unit 412. The display control unit 412 outputs the reduced color raster data to the cathode ray tube 413.

  As is apparent from the above description, in the present embodiment, when generating raster data having a predetermined number of colors based on vector data, the palette used for the color reduction processing is defined by the color explicitly described in the vector data. It was set as the structure produced | generated using information.

  This makes it possible to avoid a situation in which the color intended by the designer of the vector data is not reflected by the color reduction process.

  In addition, among the palettes used for the color reduction processing, for the color information other than the color information explicitly described in the vector data, a color having a large number of pixels among colors that can be expressed by the vector data is used.

  This makes it possible to leave a color with a large area in the color reduction process.

  From the above, high-quality color reduction processing can be realized.

[Other Embodiments]
Note that the present invention can be applied to a system (for example, a copier, a facsimile machine, etc.) consisting of a single device even when applied to a system composed of a plurality of devices (for example, a host computer, interface device, reader, printer, etc.). You may apply.

  Needless to say, the object of the present invention can also be achieved by supplying a system or apparatus with a storage medium storing software program codes for realizing the functions of the above-described embodiments. In this case, the above functions are realized by the computer (or CPU or MPU) of the system or apparatus reading and executing the program code stored in the storage medium. In this case, the storage medium storing the program code constitutes the present invention.

  As a storage medium for supplying the program code, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, or the like is used. be able to.

  Further, the present invention is not limited to the case where the functions of the above-described embodiments are realized by executing the program code read by the computer. For example, an OS (operating system) running on a computer performs part or all of actual processing based on an instruction of the program code, and the functions of the above-described embodiments may be realized by the processing. Needless to say, it is included.

  Furthermore, after the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the functions of the above-described embodiments are realized. Is also included. That is, after the program code is written in the memory, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing based on the instruction of the program code, and is realized by the processing. This is also included.

1 is a diagram illustrating a configuration of an image forming apparatus 101 according to an embodiment of the present invention. 3 is a diagram illustrating an example of vector data to be processed by the image forming apparatus 101. FIG. It is a figure which shows a mode that the vector data shown in FIG. 1 is a block diagram showing a functional configuration of an image forming apparatus 101 according to an embodiment of the present invention. 4 is a flowchart showing a flow of processing in the image forming apparatus 101. It is a figure which shows the color reduction palette produced | generated in the color reduction palette production | generation part 405. FIG. It is a figure which shows the color reduction palette produced | generated in the color reduction palette production | generation part 405. FIG. It is a figure which shows the color reduction palette produced | generated in the color reduction palette production | generation part 405. FIG. It is a figure which shows the color conversion table produced | generated in the color conversion table production | generation part 409.

Claims (8)

An image forming apparatus that generates raster data having a predetermined number of colors based on vector data described in a page description language,
Data generating means for generating raster data using all color information that can be expressed by the vector data;
Extraction means for extracting color information explicitly described in the elements described in the vector data;
Pallet generation for generating the palette with the predetermined number of colors using the color information extracted by the extraction unit and a part of the color information used for generating the raster data in the data generation unit Means,
A color conversion table for allocating color information not used for generating the palette among the color information used for generating the raster data in the data generating means to any color information constituting the palette Table generating means for generating
An image forming apparatus comprising: a color reduction processing unit that performs color reduction processing on the raster data generated by the data generation unit using the palette and the color conversion table. The palette generating means includes
The image forming apparatus according to claim 1, wherein the palette is generated by giving priority to the color information extracted by the extracting unit. The palette generating means includes
2. The palette is generated with priority given to color information having a large number of pixels in the raster data among the color information used to generate the raster data in the data generation means. Image forming apparatus. The table generating means includes
Of the color information used to generate the raster data in the data generation means, color information that was not used for generating the palette is assigned to the most similar color information among the color information included in the palette. The image forming apparatus according to claim 1, wherein the color conversion table is generated.   The image forming apparatus according to claim 1, wherein the vector data is an XML (Extensible Markup Language) file.   The image forming apparatus according to claim 5, wherein the XML file is described in an SVG (Scalable Vector Graphics) format. An image forming method in an image forming apparatus for generating raster data having a predetermined number of colors based on vector data described in a page description language,
A data generation step in which data generation means generates raster data using all color information that can be expressed by the vector data;
Extraction means, in said written in the vector data elements, an extraction step of extracting explicitly described color information,
A palette having a predetermined number of colors using the color information extracted in the extraction step and a part of the color information used to generate the raster data in the data generation step. A pallet generating process for generating
Of the color information used for generating the raster data in the data generation step by the table generation means, the color information that has not been used for generating the palette is assigned to any color information constituting the palette. A table generation step for generating a color conversion table for
An image forming method comprising: a color reduction processing step in which a color reduction processing means performs color reduction processing on the raster data generated in the data generation step using the palette and the color conversion table. A program for causing a computer to execute each step of the image forming method according to claim 7.