JP3754903B2 - Image processing apparatus, control method therefor, computer program, and storage medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus that reproduces and outputs JPEG compressed image data, a control method thereof, a computer program, and a storage medium.
[0002]
[Prior art]
In conventional image editing in color copying machines and other imaging devices, the original paper is placed on a digitizer (coordinate input device), the trimming position, etc. is specified, and scanning and printing are performed based on the position information. It was.
[0003]
In recent years, multifunctional color imaging devices having an electronic sort function and the like are appearing as the price of memory is reduced and the compression technology is improved. Image editing in an imaging device that needs to spool such a page image to memory is not performed by a digitizer or the like, but rather by using a display device such as a color liquid crystal and performing an interactive preview display on the operation screen. Editing is desirable.
[0004]
[Problems to be solved by the invention]
By the way, the original purpose of such an imaging device is print output. Recent printer engines have higher recording resolution. Most of them are 600 dpi or more. Thus, of having to spool the image read simply, how although the memory becomes less expensive, and requires a huge capacity, necessarily, has to be compressed.
[0005]
On the other hand, a display device such as a liquid crystal display device for previewing generally has a display resolution of about 72 dpi. Therefore, in order to perform the preview, it is necessary to expand the compressed high-resolution image into a plain image and perform resolution conversion to generate a reduced image for preview. At this time, the compressed image is expanded. Therefore, a larger work memory is required as the difference in resolution is larger. Further, since the preview is on the operation screen, it is necessary to frequently change the enlargement / reduction of the image even after the preview image is displayed. However, if a reduced image is generated from a high-resolution image every time, it takes a long time to generate a preview image, which may cause problems such as a slow display response speed and poor operability of the device. is expected. In order to improve the reaction speed, generating preview images with a plurality of resolutions is one means, but this consumes a large amount of memory.
[0006]
The present invention has been made in view of such a problem, and an image processing apparatus that makes it possible to reproduce JPEG compressed image data with a simple configuration and with a desired reduction ratio while suppressing memory consumption. And a control method thereof, a computer program, and a storage medium.
[0007]
[Means for Solving the Problems]
In order to solve this problem, for example, an image processing apparatus of the present invention has the following configuration. That is,
An image processing apparatus for reproducing JPEG compressed image data,
Spatial frequency data generation means for generating spatial frequency data as a DCT conversion result by performing Huffman decoding and inverse quantization on JPEG image data;
When the reduction ratio is S / 8 (S = 1, 2, 3,..., 8), S × S reduced pixel block data is obtained from the 8 × 8 spatial frequency data obtained by the spatial frequency data generating means. Reduced pixel block data generating means for generating;
Storage means for storing each S × S reduced pixel block data obtained by the reduced pixel block data generating means ;
Output means for outputting the image stored in the storage means ,
The reduced pixel block data generation means includes:
Reduction means for outputting S × S data having a direct current component as the origin in 8 × 8 spatial frequency data generated by the spatial frequency data generation means as effective data, and outputting the other as 0;
Inverse DCT conversion means for generating 8 × 8 pixel data by inverse DCT transforming the 8 × 8 data generated by the reduction means;
Of the 8 × 8 pixel data obtained by the inverse DCT conversion means, S × S pixels are used as effective pixel data, and the other pixel data are deleted, thereby reducing the S × S effective pixel data. Pixel reduction means for generating pixel block data .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.
[0009]
A configuration diagram of a JPEG decompressor in the embodiment is shown in FIG. 1 and will be described below.
[0010]
The JPEG bit stream to be decompressed is first input to the Huffman decoder 102, and the Huffman-encoded bit stream is decompressed into quantized spatial frequency data. Subsequently, the quantized spatial frequency data is input to the inverse quantization circuit 103, and the quantized spatial frequency data is expanded to the original number of bits (here, 8 bits) and aligned to 8 bits. Spatial frequency data is generated. The spatial frequency data arranged in 8 bits is input to the reduction circuit 104 in MCU units (8 × 8 pixels).
[0011]
The reduction circuit 104 operates in accordance with an external control signal (magnification designation signal). Nothing is done in the case of the same magnification, and when a reduced image is generated, the image is reduced at a magnification of 1/8 to 7/8 in the frequency space. In the case of 1/8 reduction, the reduction process is not performed, and only the DC (direct current) component obtained by the above process exists at the origin of the MCU (the upper left corner of the 8 × 8 matrix), and other spatial frequency components. 0 data is output. In the case of 4/8 times, 4 × 4 data having the MCU origin (the position where the DC component is present) as the upper left corner and 0 data for the other spatial frequency components are output. That is, in the case of S / 8 times (S = 1, 2,..., 8), S × S data with the DC line segment DC of the 8 × 8 data after inverse quantization as the origin is output, Data other than 0 is output as 0 data.
[0012]
The reduced or unchanged spatial frequency data is returned to image data in MCU units by the inverse DCT circuit 105. The data returned to the MCU unit image is input to the pixel reduction circuit 106. In the case of normal JPEG expansion at the normal magnification, an 8 × 8 pixel image is output as it is, and in the case of reduction / expansion (depending on the control signal) For example, if the magnification is 7/8, 7 × 7 pixels are clipped and output from the origin of the MCU. By performing this processing on all JPEG bitstreams, JPEG decompression can be performed, and at the time of reduction, the magnification is reduced in units of MCU. 1/1, 7/8, 6/8, 5/8, 4/8, 3 Images of / 8, 2/8, and 1/8 are obtained.
[0013]
FIG. 2 is a schematic diagram showing a one-dimensional operation of the reduction circuit 104. The images arranged in the frequency space are reduced (in this case, 6/8 times) and output as the lower data in the figure. The actual reduction circuit 104 performs this processing for the two dimensions of X and Y.
[0014]
FIG. 3 is a schematic diagram showing how the image is reduced. The 8 × 8 pixel MCU 301 compressed in the JPEG format is reduced to 6/8 times by the reduction circuit 104, and is expanded in the memory as a 6 × 6 pixel image 311 by the pixel reduction circuit 106. The subsequent MCU 302 is also reduced by 6/8, and is expanded as an image 312 on the memory without leaving an interval with the image 311. By repeating this, a reduced image is generated.
[0015]
FIG. 4 is a block diagram showing a system configuration of the imaging apparatus (digital color copying machine) of the present embodiment. The JPEG decompressor shown in FIG. 1 is employed in the JPEG decoder 101 in FIG. Further, CPU 402 would also output Contact Keru control signal in FIG. Hereinafter, the configuration of FIG. 4 will be described together with its operation.
[0016]
An image scanned by the scanner 406 is taken into the multi-function controller 401 via the scanner interface 407. The captured image is stored in the main memory 403 via the crossbar circuit 404. The CPU 402 compresses the captured image and spools it in the main memory 403. The spooled image is once decompressed to a 1/8 resolution plain image using the JPEG decompressor 101, and then JPEG compressed again as a 1/8 resolution image for previewing, and stored in the memory 403. As a result, the main memory 403 stores JPEG data of the resolution of the read image and 1/8 JPEG data.
[0017]
The CPU 402 determines the size of the preview image, generates a plain image having a desired resolution from the high-resolution original image or the preview 1/8 image by the JPEG decompressor 101, and copies (transfers) it to the VRAM 413 of the display unit 411. The plain image copied to the VRAM 413 is displayed on the LCD 412 as a preview image. Note that the display unit 411 is provided with an input unit 414 for inputting various instructions, and one of them is a coordinate input plate (touch panel) provided on the front surface of the LCD 412.
[0018]
The spool compressed image data designated for printing by the user is decompressed by the image decompression circuit 101, rotated by the image processing circuit 410, and then printed on paper by the printer 408 via the printer interface 409. In the case of a network scan operation, the spooled compressed image data is sent to the host 413 via the network interface 405.
[0019]
FIG. 5 is a schematic diagram showing a page image format of the present embodiment. One page image is divided into 32 × 32 pixel tiles and JPEG compressed in tile units. An A4 600 dpi image corresponds to 155 × 216 tiles. A reduced image of 1/8 resolution corresponds to 20 × 27 tiles. During JPEG compression, 32 × 32 pixels are further divided into 8 × 8 pixel MCUs. The JPEG decompressor 101 performs image reduction in this MCU unit.
[0020]
FIG. 6 is a flowchart showing a preview operation sequence (mainly the CPU 402). In the following description, it is assumed that the document image is JPEG compressed from the scanner 406 and read into the main memory 403.
[0021]
First, a 1/8 resolution plane image is created from the high resolution original image (stored in the main memory 403) using the JPEG decompressor 101 (step S601). Subsequently, the created 1/8 resolution plane image is divided into tiles shown in FIG. 5, and JPEG compression is performed in units of tiles (step S602). As a result, the JPEG compressed data of the original high resolution image and 1/8 resolution image is held in the memory 403 (step S603).
[0022]
Subsequently, from the 1/8 resolution image, the JPEG decompressor 101 is set to a 4/8 times reduction mode, and a 1/16 resolution plain image used for actual preview is created (step S604). Then, by copying a 1/16 resolution plain image to the VRAM 413, a preview image can be displayed on the LCD 412 (step S605).
[0023]
Subsequently, it is determined whether or not the user desires to enlarge or display the preview image from the input unit 414 of the display unit 411 (step S606). If the resolution is higher than 1/8 resolution (step S608), if the resolution is high, the tile necessary for display is cut out from the original high resolution image using the tile management information (step S609), and the cut high A plane image is created from a desired tile of the resolution image at a desired reduction ratio using the JPEG decompressor 101 (step S610), and the plane image is copied to the VRAM 413 and enlarged display is performed (step S605).
[0024]
If the image requested to be displayed is lower than 1/8 resolution, a desired tile is cut out from the 1/8 resolution JPEG compressed image data (step S611), and the desired 1/8 resolution image is cut out. A plain image is created from the tile using the JPEG decompressor 101 at a desired reduction ratio (step S612), and the plain image is copied to the VRAM 413 to display a preview (step S605). As a result, a reduction ratio of 1/8 to 1/64 can be obtained by using 1/8 resolution JPEG compressed image data.
[0025]
If the user operation is neither enlargement nor reduction of the preview, it is next determined whether the preview processing of the image is completed (step S607). If not completed, the process returns to determination of whether the operation is expansion or reduction (step S607). S606), if it is finished, it is judged whether the next preview processing is another image (step S608). If the preview is another image, a 1/8 resolution plain image of the other image is created by the JPEG decompressor 101. (Step S601) If it is not a preview process for another image, the preview process is terminated.
[0026]
FIG. 7 is a schematic diagram showing how the preview image is displayed in the present embodiment. Preview processing First, an image 701 of 1/16 resolution of the entire page is displayed on the LCD 412. When the user designates enlargement (touching the enlargement button), the CPU 402 determines an enlargement request (step S606), and since the user's request is twice the enlargement of the preview image, the image becomes 1/8 resolution. In the resolution determination (S608), the 1/8 resolution retained image is selected, and the tiles necessary for display in contact with the origin of the 1/8 resolution image are cut out (step S611), and developed by the JPEG decoder 101 at the same magnification. Thus, a preview plane image of 1/8 resolution image is created (step S612), and an enlarged preview image 702 is displayed on the LCD 412 by copying the image to the VRAM 413.
[0027]
In the above example, enlargement / reduction of the preview display when the document is read has been described. However, editing processing such as trimming is performed as a separate process. In any case, when the editing process is completed, a process corresponding to the editing instruction is performed, and the printer engine 408 prints out.
[0028]
As described above, according to the present embodiment, the image can be reduced to 1/8 times simultaneously with JPEG expansion, the work memory can be reduced, and a high-resolution image can be tiled using a JPEG expander. Each tile is JPEG-compressed and stored and managed, and a low-resolution image is generated from this high-resolution image, stored, cut out in tile units, JPEG decompression, and scaling are performed. The preview processing of the display unit can be performed at high speed.
[0029]
Further, according to the present embodiment, the original document is JPEG compressed and stored, and the 1/8 resolution plane image is further JPEG compressed and stored, so that 8/8 to 1/8 and 1/8 to 1/64. It is possible to freely generate an image with double the resolution.
[0030]
In the embodiment, the example applied to the copying machine has been described. However, the present invention is not limited to the above embodiment because the present invention may be applied to any apparatus as long as it can display an image as a preview. Absent.
[0031]
The compression and decompression processing in the above-described embodiment can also be applied to a general-purpose information processing apparatus such as a personal computer that reads and displays the data from a scanner or a storage medium storing JPEG compressed data. In this case, since most of the processing (the portion corresponding to the block diagram of FIG. 1 and the processing according to the flowchart of FIG. 6) is performed by software, the present invention can also be applied to software incorporated in an information processing apparatus. When software is installed in a computer, a storage medium (floppy disk, CDROM, etc.) that stores the program is usually set in the apparatus and copied or installed. A medium is also included in the present invention.
[0032]
【The invention's effect】
As described above, according to the present invention, it is possible to reproduce JPEG compressed image data at a desired reduction ratio with a simple configuration and with reduced memory consumption.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram of a JPEG decompressor according to an embodiment.
FIG. 2 is a schematic diagram illustrating an operation of a reduction circuit in the embodiment.
FIG. 3 is a schematic diagram illustrating a state before and after image reduction in the embodiment.
FIG. 4 is a system block configuration diagram in the embodiment.
FIG. 5 is a diagram illustrating an image format in the embodiment.
FIG. 6 is a flowchart illustrating an operation process of a preview operation according to the embodiment.
FIG. 7 is a schematic diagram showing a display state in the embodiment.

Claims (7)

An image processing apparatus for reproducing JPEG compressed image data,
Spatial frequency data generation means for generating spatial frequency data as a DCT conversion result by performing Huffman decoding and inverse quantization on JPEG image data;
When the reduction ratio is S / 8 (S = 1, 2, 3,..., 8), S × S reduced pixel block data is obtained from the 8 × 8 spatial frequency data obtained by the spatial frequency data generating means. Reduced pixel block data generating means for generating;
Storage means for storing each S × S reduced pixel block data obtained by the reduced pixel block data generating means ;
Output means for outputting the image stored in the storage means ,
The reduced pixel block data generation means includes:
Reduction means for outputting S × S data having a direct current component as the origin in 8 × 8 spatial frequency data generated by the spatial frequency data generation means as effective data, and outputting the other as 0;
Inverse DCT conversion means for generating 8 × 8 pixel data by inverse DCT transforming the 8 × 8 data generated by the reduction means;
Of the 8 × 8 pixel data obtained by the inverse DCT conversion means, S × S pixels are used as effective pixel data, and the other pixel data are deleted, thereby reducing the S × S effective pixel data. An image processing apparatus comprising: a pixel reduction unit that generates pixel block data . Further, when JPEG image data is given, compression means for generating a 1/8 reduced image by the reduced pixel block data generating means and JPEG compressing the 1/8 reduced image;
Selecting means for selecting either the JPEG compressed image data or the 1/8 JPEG compressed image compressed by the compression means according to a specified magnification;
The image processing apparatus according to claim 1 , wherein the selected JPEG compressed image data is output through the reduced pixel block data generation unit and the storage unit. A control method of an image processing apparatus for reproducing JPEG compressed image data,
A spatial frequency data generation step of generating spatial frequency data as a DCT conversion result by performing Huffman decoding and inverse quantization on JPEG image data;
When the reduction ratio is S / 8 (S = 1, 2, 3,..., 8), S × S reduced pixel block data is obtained from the 8 × 8 spatial frequency data obtained in the spatial frequency data generation step. A reduced pixel block data generation step to generate;
A storage step of storing each S × S reduced pixel block data obtained in the reduced pixel block data generation step ;
An output step of outputting the image stored in the storage step ,
The reduced pixel block data generation step includes:
A reduction step of outputting S × S data having a direct current component as an origin in 8 × 8 spatial frequency data generated in the spatial frequency data generation step as effective data and outputting the other as 0;
An inverse DCT conversion step of generating 8 × 8 pixel data by performing inverse DCT conversion on the 8 × 8 data generated in the reduction step;
Of the 8 × 8 pixel data obtained in the inverse DCT conversion process, S × S pixels are used as effective pixel data, and the other pixel data are deleted, thereby reducing the S × S effective pixel data. A control method for an image processing apparatus, comprising: a pixel reduction process that generates pixel block data . A computer program that functions as an image processing apparatus that reproduces JPEG compressed image data by being read and executed by a computer, the image processing apparatus comprising:
Spatial frequency data generation means for generating spatial frequency data as a DCT conversion result by performing Huffman decoding and inverse quantization on JPEG image data;
When the reduction ratio is S / 8 (S = 1, 2, 3,..., 8), S × S reduced pixel block data is obtained from the 8 × 8 spatial frequency data obtained by the spatial frequency data generating means. Reduced pixel block data generating means for generating;
Storage means for storing each S × S reduced pixel block data obtained by the reduced pixel block data generating means ;
Functions as output means for outputting the image stored in the storage means,
The reduced pixel block data generation means includes:
Reduction means for outputting S × S data having a direct current component as the origin in 8 × 8 spatial frequency data generated by the spatial frequency data generation means as effective data, and outputting the other as 0;
Inverse DCT conversion means for generating 8 × 8 pixel data by inverse DCT transforming the 8 × 8 data generated by the reduction means;
Of the 8 × 8 pixel data obtained by the inverse DCT conversion means, S × S pixels are used as effective pixel data, and the other pixel data are deleted, thereby reducing the S × S effective pixel data. Pixel reduction means for generating pixel block data
A computer program that functions as: Computer-readable storage medium characterized by storing a computer program according to claim 4. In an image processing apparatus that reads a document with a reading unit and prints it out,
A first storage unit that compresses image data obtained by reading by the reading unit using a JPEG compression unit and stores the compressed image data in a predetermined storage unit;
Spatial frequency data generation means for generating spatial frequency data as a DCT conversion result by performing Huffman decoding and inverse quantization on the JPEG compressed image data stored in the first storage means ;
S × S reduced pixel block data from 8 × 8 spatial frequency data obtained by the spatial frequency data generating means at a given reduction ratio S / 8 (S = 1, 2, 3,... 8). Reduced pixel block data generating means for generating
A reduction ratio 1/8 is set in the reduced pixel block data generating means, reduced image data composed of the generated reduced pixel block data is generated, and reduced JPEG compressed image data is generated using the JPEG compression means. Second storage means for storing in the storage means;
Based on the reduction ratio designated at the time of preview display, either the JPEG compressed image data stored by the first storage unit or the reduced JPEG compressed image data stored by the second storage unit is stored. Display means for selecting and displaying a preview of the image data obtained through the spatial frequency data generation means ,
The reduced pixel block data generation means includes:
Reduction means for outputting S × S data having a direct current component as the origin in 8 × 8 spatial frequency data generated by the spatial frequency data generation means as effective data, and outputting the other as 0;
Inverse DCT conversion means for generating 8 × 8 pixel data by inverse DCT transforming the 8 × 8 data generated by the reduction means;
Of the 8 × 8 pixel data obtained by the inverse DCT conversion means, S × S pixels are used as effective pixel data, and the other pixel data are deleted, thereby reducing the S × S effective pixel data. An image processing apparatus comprising: a pixel reduction unit that generates pixel block data . In a control method of an image processing apparatus that reads a document with a reading unit and prints it out
A first storage step of compressing image data obtained by reading by the reading unit using a JPEG compression unit and storing the compressed image data in a predetermined storage unit;
A spatial frequency data generation step of generating spatial frequency data as a DCT conversion result by Huffman decoding and inverse quantization of the JPEG compressed image data stored in the first storage step ;
S × S reduced pixel block data from 8 × 8 spatial frequency data obtained in the spatial frequency data generation step at a given reduction ratio S / 8 (S = 1, 2, 3,... 8). Reduced pixel block data generating step for generating
A reduction ratio 1/8 is set in the reduced pixel block data generation step, reduced image data composed of the generated reduced pixel block data is generated, and reduced JPEG compressed image data is generated using the JPEG compression means. A second storage step for storing in the storage means;
Based on the reduction ratio specified in the preview display, either the JPEG compressed image data saved in the first saving step or the reduced JPEG compressed image data saved in the second saving step is stored. Selecting and displaying a preview of the image data obtained through the spatial frequency data generation step ,
The reduced pixel block data generation step includes:
A reduction step of outputting S × S data having a direct current component as an origin in 8 × 8 spatial frequency data generated in the spatial frequency data generation step as effective data and outputting the other as 0;
An inverse DCT conversion step of generating 8 × 8 pixel data by performing inverse DCT conversion on the 8 × 8 data generated in the reduction step;
Of the 8 × 8 pixel data obtained in the inverse DCT conversion process, S × S pixels are used as effective pixel data, and the other pixel data are deleted, thereby reducing the S × S effective pixel data. A control method for an image processing apparatus, comprising: a pixel reduction process that generates pixel block data .

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