JPH03144780A - Image compressing system - Google Patents

Abstract

PURPOSE:To obtain a high image data compression ratio without losing picture quality by sorting image data in accordance with their properties or purposes and selecting the optimum image compressing method to execute compression processing. CONSTITUTION:An image compression method selecting means selects an image compressing method in accordance with a sort inputted by an image sort inputting means 20 for sorting plural image data in accordance with their properties or purposes. An image compressing means compresses the image data by the selected image compressing method and records the compressed data in a recording medium 32. Namely, the image data are sorted in accordance with their properties or purposes, selects the optimum image compressing method and then executes the compressing processing. Consequently, a high compression ratio can be obtained without losing the picture quality and the data volume can sharply be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to digital image processing, and particularly to an image compression method for encoding image data.

<Prior art> Various video displays, including large projectors, have been used in place of conventional OHPs, slide projectors, etc., as a means of displaying multiple image data in a composite manner at conferences and lectures. devices are starting to become popular. Unlike conventional video display devices, these display devices are based on electronic means supported by the reduction in the cost of semiconductor devices such as memory, and use a personal computer to create a composite image for display from multiple image data. , and displaying that image on a large screen.

Conventionally, the method of synthesizing and displaying multiple image data using a computer, etc. is to digitize a color photograph or word processing output with a camera or scanner, import it into a memory, etc., and then scale, crop, and layout the image data. etc. to create an image for display. The display image created in this way is recorded on a recording medium such as a magnetic disk or a floppy disk, and is transported to a conference hall or lecture venue where a composite display is performed.

<Problems to be Solved by the Invention> Since the above-described system for displaying a plurality of image data in a composite manner deals with the image data itself, the problem is that the amount of data is large. In particular, when taking created images to a conference or lecture, it is desirable to use a compact recording medium, and for this purpose, it is better to have a smaller amount of data for the same image data. To this end, it has been conventional practice to compress full-color images to reduce the amount of data by taking advantage of the fact that the human eye is relatively insensitive in areas of high spatial frequency.

However, in such applications, as illustrated in FIG. 6(a), a full-color image 6I is used as a background, appropriate partial images 62 are laid out on top of the full-color image 6I, and characters 6 for explanation are further added.
3 may be displayed overlapping each other. If you compress a full-color image in which such character and figure images are superimposed using a compression method that takes advantage of the insensitivity of the human eye in areas with high spatial frequencies as described above, if you try to obtain a normal compression rate, the character and figure parts will be compressed. There was a problem in that the deterioration of the character and graphic parts was noticeable, and conversely, if the deterioration of the character and graphic parts was to be reduced, the compression ratio had to be lowered. Furthermore, in the case of meetings and lectures, there is a method of changing part of the image to enhance the display effect. wJ6 figure (
In b) and (C), the chair 64 is displayed in a different position with the same room as the background.

In this way, when displaying the same partial image on the same background image by changing its position, or when displaying multiple text and graphic images or partial images on the same background image while changing them, In the conventional technology, a large number of images in which only a portion has changed are stored separately on a recording medium, which inevitably results in a large amount of data.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image compression method for displaying multiple image data in a composite manner, which can obtain a high compression rate without degrading image quality and can significantly reduce the amount of data. There is a particular thing.

Means for Resolving Line Order> In order to achieve the above object, the present invention is an image compression method for displaying a plurality of image data in a composite manner, and the present invention is an image compression method for displaying a plurality of image data in a composite manner. Therefore, an image classification input means for classification and the image classification input element 1 are provided.
an image compression method selection means for selecting an image compression method according to the classification inputted by the step; and compressing the image data using the image compression method selected by the image compression method selection means and recording it on a recording medium. According to the image compression method of the present invention, image data is classified according to its nature or use, and then the most suitable image compression method is selected for compression processing. Therefore, compression processing can be performed according to the nature of the image data, such as whether it is a character/figure image or other image, and compression processing can be performed according to the purpose of the image data, such as the entire image that is the base or partial images that change. .

<Embodiment> Hereinafter, an image compression method according to the present invention and a system for displaying a plurality of image data in a composite manner using the same (hereinafter referred to as "electronic presentation system") will be described. FIG. 2 shows the hardware configuration of the system used for electronic presentations, and FIG. 3 shows the flow of image data that can be pressed into this system.

This system is roughly divided into an editing system and a display system.

Display equipment is used to display images at presentations such as conferences and lectures, and is equipped with large projectors and multiple CRT monitors, and can display images created by editing equipment, with cursors and arrows. It is possible to display a pointer such as on the screen, or to execute image change processing set in advance on an editing system while the image is being displayed.

On the other hand, editing devices are used to create images to be displayed on display devices, and are used to edit and create images, set the display order of multiple images, set image change processing for display raw images, and perform the change processing. Configure the switch for startup. A display program consisting of image data, image display order data, image change processing data, etc. created by an editing system is written on a compact recording medium such as a floppy disk and delivered to a display system.

The system shown in FIG. 2 for displaying a plurality of image data in a composite manner using the image compression method according to the present invention serves both as the above-mentioned editing system and display system. The button 20 in the figure is a pull color scanner, which is used to digitize and capture not only images such as photographs and paintings, but also characters, sentences, graphs, and the like. Reference numerals 21 and 22 denote a keyboard and a mouse, respectively, which are used for inputting various operational instructions, file names, and the like. The CPO 23 controls the entire system and has internal memory and the like for storing various control programs. Image memory 24
In this case, image data to be displayed on the monitor 25 is written. It has the capacity to store image data equivalent to several pages. The memory 26 is for temporarily storing a display program created by an editing system. The magneto-optical disk device 28 is a large-capacity storage device, and is used as an image database 32 in FIG. On the other hand, the floppy disk device indicated by the reference numeral 27 in FIG. 2 is used as an example of a compact recording device, and corresponds to the recording medium 34 in FIG. 3. The DSP 29 is a digital signal processor and performs compression encoding and decoding of images.

Image data or compressed data is transferred between the image memory 24 and the DSP 29 by the CPU 23 via the FIFO or common memory shown in FIG. The common memory can be accessed by switching between access from the CPU 2B and access from the DSP 29.

Next, an outline of the flow of image data will be explained using FIG.

In this method, not only color photographs but also characters, sentences, graphs, etc. are imported as images from outside and created. That is, a pull color scanner 20 is provided as an image input means, and images such as photographs, stamp documents, and word processor printouts are input, and images are edited and created by performing scaling, affine conversion, coloring, shading, layout processing, etc. conduct.

First, a full color scanner 20 is used to capture an image. It can be imported from photographs, printed matter, or the printout of the hoop opening. The captured images are then stored in the image database 82.

As mentioned above, in this system, the magneto-optical disk 28
is used as the image database 82.

Editing and creating image data for presentations is carried out in the editing system 33 using the image database 32 as necessary.
This is done by extracting image data from the computer and performing various processing while displaying it on the monitor 25. The components of the presentation image created in this way are compressed using the image compression method according to the present invention and stored in the image database 32 again. Next, the editing system 33 creates a display program consisting of position data for arranging the component parts, data for image change processing, etc., and stores this display program and the image data of the component parts in the storage medium 34. . As mentioned above, this system uses the floppy disk device 27 as the storage medium 34. The display device 35 receives a display program and image data from the storage medium 34, creates an image from these data at the time of display, and performs a presentation.

Next, the editing and creation work of image data and the image compression method according to the present invention will be explained with a focus on image data compression processing using FIG. 1 and FIGS. 4 and 5.

1. A schematic processing flow is shown in FIG. 4. As shown by reference numeral 4I, the original image is captured into the image database 82 using the full color scanner 20. At this time, generally, the full-color entire image and character/graphic images such as those output by a word processor are input separately. Next, character and graphic images, full-color entire images, and full-color partial images that are to become component parts are extracted and converted into files. This operation not only searches for necessary images from among the images that have been input separately and stored in the image database 32 as described above, but also cuts out images that you want to treat as partial images within the entire full-color image, and Cutting out text and graphic images from the entire image is performed. The image data as a component created in this way is first stored in the image database 32 again with an appropriate file name for compression processing. Thereafter, in step 43, compressed data is created and converted into a file. Details of compressed data creation and file creation are shown in Figure 1. In this embodiment, the file is once created before creating the compressed data, but the data may be compressed directly after creating the component parts. In steps 1 to 3 in FIG. 1, press button 42 in FIG. 4 to input the image file name of the filed component from the keyboard 21 or mouse 22, and compress the image data while displaying it on the monitor 25. Choose an image. The compressed data file name is assigned depending on whether the selected component is a text/graphic image, a full-color entire image, or a partial full-color image. This distinction is made by adding an identifier to the beginning or end of the file name. The compressed data file salt attached in this way is the keyboard 2
Inputs are made as shown in 4 in FIG. 1, starting with the first prize. Next, if the input compressed data file name has an identifier for a text/graphic image, the process branches from 5 to 10 in FIG. 1 to compress the text/graphic image and record it in the image database 32 again. In addition, if the compressed data file name has an identifier for a full-color entire image, the range is 6 to 9. If the compressed data file name has an identifier for a full-color partial image, it is 7.
Then, the process branches to step 8, and the optimum image compression method is executed depending on the nature or purpose of each image, and the results are recorded in the image database 32 again.

Examples of the three image compression methods described above will be described below.

L Text/Graphic Image Compression Method The text/graphic image compression method in this system is suitable for images with strong binary image properties such as characters and graphics.

(Patent application No. 63-281129. Patent application No. 1-109914
, see Japanese Patent Application No. 1-106128. ) The processing procedure is usually
Extracts only the luminance component of the image, requantizes it, and then divides it into the "target part" (text, figures, etc.), "background part", and "halftone part", and uses run-length encoding as the basic method. It is encoded using a method.

In the case of characters, figures, etc., their shape and brightness information (or density information) for anti-aliasing are required.
The color information of the document can be provided separately at the time of decoding and is therefore not required at the time of encoding.

Therefore, in the text/graphic image compression method, only the luminance component is compressed and encoded, and the color information of the document is discarded.

Next, the luminance acid image is requantized to the required number of gradations. When dealing with a normal display of about 500 x 500 pixels, considering the number of gradations required for anti-aliasing, etc., quantization may be performed with 2 to 3 bits. Requantization uses histogram processing to reduce the pixel value of the target area to the minimum value, the pixel value of the background area to the maximum value, and
The quantization divisions are determined so that the required number of tones are used to divide between the two values, and furthermore, halftone parts can be created only at the boundary between the target part and the background part, so that the halftone part can be created only at the boundary between the target part and the background part. Make sure to remove the key parts.

Next, the requantized image is encoded. A feature of the image to be encoded is that there are very few halftone parts. An encoding method that takes advantage of this feature will be described next. First, the image is divided into a portion with the minimum pixel value (target portions such as characters and figures), a portion with the maximum pixel value (background portion), and other halftone portions.

For halftone parts, convert the image to bitbrain 1
, O. Among these, the minimum pixel value part, the maximum pixel value part, and the MSB value (0, 1
) for the above four types, and perform variable length encoding. A 2-bit flag is attached to the run length code so that it can be determined to which classification the run belongs.

In the image, the pixels with the minimum pixel value and maximum pixel value, and the MSB
The bit-brane information of is processed by encoding here 1. For the remaining halftone portion, information on bit planes other than the MSB bit plane is encoded as follows. That is, for each brane, a run length of 1, O is determined and variable length coding is performed. At this time, the minimum pixel value part and maximum pixel value part that have already been encoded are skipped, and only the halftone part is skipped. Collect and find the run length,
Perform variable length encoding. Variable length encoding includes MH encoding and M
It is possible to use R encoding.

2. Full-color entire image compression method The full-color entire image compression method is a method for compressing an entire full-color image, and uses a compression method using block encoding. (Special application 1986-2+8019
, see Japanese Patent Application No. 61-254377. ) image data
Perform IQK conversion and compress each YIQ image. 1, 7
The image is divided into blocks of 4×4 pixels. In each block, the dispersion of pixel values is examined and classified into three modes. In mode 0, which has the smallest variance, only the average value of pixels within a block is encoded. Next is the mode with the highest variance! Now, an average value, one difference value, and one bit brain are created, and when decoding, the pixel value within the block is encoded so that it can be represented by two representative values. Furthermore, in mode 2, which has the largest variance, an average value, a difference value, and two bit brains are created, and the pixel value is encoded so that it can be represented by four representative values when decoded. In the I, 0 image, detailed information is 7
Since no image is needed, each block is divided into 4×4 pixels, and then each block is encoded in mode O1 or only in mode 1. During playback, filter processing is performed to reduce block distortion.

3. Full-color partial image compression method The full-color partial image compression method is a method of compressing and encoding only a partial area in a full-color image. (Patent application 1986-195854, Patent application 1982-66819.6
See 6820.66821. ) The shape of the region is arbitrary, and there may be holes in the region.

A region is represented by adding data to each pixel indicating whether it is a region or a boundary portion. This data is called area information. The area information is information on L bits of each pixel, and has a value of 2-
When the value is 1, it is inside the area, when the value is 00, it is outside the area, that is, the background, and when the value is 1 to 2-2, it is the boundary part. When superimposing full-color partial images, this value represents a pixel-by-pixel mixing ratio of the full-color partial image and the background image to be superimposed. To create region information for a partial image from an original image, a color difference extraction method that takes advantage of the difference in color between the object and the rest of the background is used. The area information is encoded using run-length encoding for pixels with a value of 0.2L-1, and for other areas, the original value is used as its t1 code. Alternatively, since the properties of the area information are the same as those of the text and graphics images described above, it is also possible to use a compression method for text and graphics images.

The image information is encoded only in the portion where the area information has the value 2L-1. In the boundary area, the image information of the original image is not encoded, but is interpolated from pixel values within the area during reproduction. The same compression method as the full-color whole image compression method is used to encode the image information, and when the image is divided into blocks, only the blocks containing pixels within the region are processed. During the decryption process, 1.
Decode area information. As a result, it is possible to know where the area on the screen (that is, the area in which the image information must be reproduced) is, and the reproduced image information can then be written into the area. Parts other than the area are
One casing of the original pixel value is left without any processing. For the boundary part, the decoded value of the nearby pixel in the area and the pixel value of the background pixel at that position are calculated according to the value of the area information at that position.
Let's mix it up and write the value.

An example of the compression method has been described above for each of the three types of image data.

Now, returning to FIG. 4 again, at 44, display program creation and editing work is performed. Through this operation, as shown in FIG. 5, a display program consisting of data on the display order of each component, data on image change processing, etc. is created. Here, memories for two images are prepared in the image memory 24 of FIG. 2 and are called screen 2 and screen 2, respectively. 1.1 in Figure 5
Select an image for the background from 00 to 103. Next 104-10
In step 9, it is determined whether or not to combine the partial image with the background image, and the files to be combined, the coordinates of the combining position, etc. are determined.

Furthermore, in steps 110 to +14, the file of the character/figure image to be synthesized with the image created in steps 100 to +09, the coordinates of the synthesis position, etc. are determined. button, 103, 109, 1 in the same figure
The purpose of storing the restoration command name in step 14 is for error handling. Generally, screen 2 is used to save images before composition. As described above, one presentation image is edited, but in reality, the above process is repeated to create a plurality of screens.

The display program created in this way is temporarily stored in the memory 26.

Next, in FIG. 4, the display program is completed by adding image change processing, pointer display commands, etc. to the display program created in step 44.

Finally, in step 46, the display program and the image compression data used therein are recorded on the recording medium 34. This recording medium 34 is divided in advance into an area for recording a display program and an area for recording compressed image data, and each data is stored in a separate area.

The data for the composite display created in this way is transported to a conference hall or a lecture hall, and the composite display is performed. When actually performing composite display (47 in Figure 4), CPO23
Compressed data file names of a plurality of images to be displayed in a composite manner are read from a display program recorded in the recording medium 34. Next, the KCPU 2i11 restores the compressed data corresponding to each of the seven isle names using a restoration method corresponding to each compression method, and then displays the images in a superimposed manner. In this way, a composite image of the white cane is displayed. A meeting or lecture will be held by repeating the above composite display operation.

<Effects of the Invention> As explained above, according to the image compression method of the present invention,
The image data is classified according to its nature or purpose, and then the most suitable image compression method is selected and compressed.
Compression processing can be performed according to the nature of the image data, such as whether it is a character/figure image or other images, and compression processing can be performed according to the purpose of the image data, such as the entire image that is the base or partial images that change. It has been possible to provide an image compression method for displaying a plurality of image data in a composite manner, which can obtain a high compression ratio of image data without degrading the image quality, and can significantly reduce the amount of data.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the image compression method of the present invention, FIG. 2 is a system configuration diagram of the present invention, FIG. 3 is an explanatory diagram of the flow of image data of the present invention, and FIG. 4 is an explanatory diagram of the image compression method of the present invention. FIG. 5 is a diagram for explaining the method of creating a display program according to the present invention, and FIG. 6 is a diagram showing an example of a presentation screen.

Claims (1)

[Claims] 1. An image compression method for displaying a plurality of image data in a composite manner, comprising an image classification input means for classifying the plurality of image data according to their properties or uses; and the image classification. an image compression method selection means for selecting an image compression method according to the classification input by the input means; and compressing the image data using the image compression method selected by the image compression method selection means and recording it on a recording medium. An image compression method comprising an image compression means for.