JP3075028B2 - Image processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for handling digital images, and more particularly to an image processing apparatus having an improved method for displaying a limited color image.

[0002]

2. Description of the Related Art In recent years, an image processing apparatus that handles digital images has generally become able to handle color images. Normally, when dealing with a full-color image, if each of the red (R), green (G), and blue (B) colors has 8 bits, 24 bits are required to represent one pixel, and the entire image is required. A fairly large storage capacity is required. For example, in the case of a full-color image composed of 1000 × 1000 pixels, 1000 × 10
00 × 24 = 24000000 bits, that is, about 3 megabytes of data. Under these circumstances, many systems that limit the number of colors that can be used at the same time and express one pixel with 8 bits are widely used.

In this limited color system, 256
Since only colors can be used, when multiple application softwares that use many colors are operated on a multi-window system, the color of the system side window changes every time the cursor moves in and out of each application window. . This occurs because the color map of the system is rewritten with the color map data of the application as the control shifts to the application side. Normally, several colors are already used in the multi-window system, so if any application that uses 256 colors is started, the above-described color switching always occurs. This phenomenon is particularly serious when dealing with a color image using many colors.

On the other hand, a method has been devised in which, for example, data stored in a file as full-color data is expressed using limited colors when displayed. For example, JP-A-2-1
No. 076 describes a specific method for determining a limited color. By setting a small number of colors, it is possible to create a display image having a relatively good appearance with a small number of colors. In addition, there are many methods of creating a display image with a small number of colors by adopting a dither or error diffusion method. As described above, if a full-color image can be expressed with a small number of colors, color switching can be avoided as much as possible.

[0005]

Here, the structure of the limited color image will be described with reference to FIG. As shown in FIG. 7, a limited color image represented in RGB requires a full color correspondence table called a color map as its color information, and the limited color image data is represented by a series of indices of the color map. ing. In FIG. 7, a circle represents one pixel, and a numerical value in the circle represents an index representing the pixel. The color map data has an index of 0 to 255 for each pixel.
, Three components (R, G, B) representing full color, and values 0 to 255 indicating the brightness of each component, where 0 is the darkest (or weakest) and 255 is the value indicating the brightness. Brightest (or strongest). For example, if the index of a certain pixel is a numerical value of 1, then 2 in the color map
Looking at the data of the 1st (1 in the index). In FIG. 7, since this data is (0, 0, 0), the color of this pixel is actually black. There are many devices that further limit the number of colors in order to avoid color switching even for such a limited color image and express the image with fewer colors.

However, the image data already stored in the file as the limited color image is
Usually, a limited color suitable for outputting the image to a display device or the like is selected. That is, since the limited color image has already lost much color information, there is a problem that if the color is further limited, the image quality is extremely reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image processing apparatus capable of minimizing the occurrence of color switching without extremely lowering the image quality of a color image.

[0008]

In order to solve the above-mentioned problems, in an image processing apparatus according to the present invention, a display means capable of simultaneously displaying a maximum of m (m> 1) limited colors;
File means for holding color image data consisting of (m ≧ n> 1) limited colors together with a first color map for associating the limited colors with full colors; and storing the first color map from the file means. Image file reading means to be read, and k (n ≧ k> 0) colors actually used by the color image data are extracted from n colors of the first color map read by the image file reading means. A use color extracting means, and a r color actually used in a second color map used by the system for display on the display means, and a k color extracted by the use color extracting means. And (r +
k) ≦ m, (m−m−m−k) of the second color map
A third color map is created by allocating k colors used in the color image data to r) unused entry portions, and when (r + k)> m, the third color map is obtained by using the second color map. The number of colors to be used is reduced to (mk), and k unused entry portions of the second color map are secured,
A color map creating means for creating a third color map by allocating k colors used in the color image data to the reserved unused entry portion, and a third color map created by the color map creating means And a color image reconstructing means for recreating the color image data.

[0009]

The used color extracting means extracts k (n ≧ k> 0) colors actually used by the color image data, and the color map creating means is used by the system as the display means. The relationship between the r color and the k color extracted by the used color extracting means is examined. If (r + k) ≦ m, the color image is stored in (m−r) unused entry portions of the second color map. Assign k colors used in the data, and (r +
If k)> m, the number of colors used in the second color map is reduced to (m−k), and k unused entry portions of the second color map are secured, and the secured unused portion is used. A third color map is created by assigning k colors used in the color image data to the entry section. The color image reconstructing means recreates color image data according to the created third color map.

According to this, when r + k ≦ m, all r used colors of the apparatus are included in the color map, and k used colors of the image data are allocated to the remaining space. Therefore, since the colors used by the apparatus and the colors used by the image data can be used as they are, color switching can be avoided. In the case of r + k> m, all the used colors of the image data are allocated, but the number of used colors of the device is reduced to m−k, so that some used colors are not included. Therefore, although color switching occurs for some colors, the colors used in the image data can be used as they are, so that it is possible to prevent the image quality of the color image from deteriorating.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image processing apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a functional configuration of an image processing apparatus according to an embodiment. The image processing apparatus 10 includes an image display unit 11, a file device 12, an image reading unit 13, a used color extracting unit 14, a color map creating unit 15, and an image reconstructing unit 16.

The image display means 11 is a display device for performing multi-window display, and can simultaneously display a maximum of m (m> 1) limited colors.

The file device 12 is a storage device that stores color image data of an application in a file format. In this embodiment, the limited color image data of n (m ≧ n> 1) (hereinafter referred to as image data) is used. Holding).

The image reading means 13 reads from the file device 12 a color map for associating image data consisting of n colors with full colors.

The used color extracting means 14 scans the image data read by the image reading means 13 and extracts k (n ≧ k> 0) colors actually used among the n colors.

The color map creating means 15 uses the r colors actually used in the color map used in the apparatus (hereinafter also referred to as a system) and the image data obtained from the used color extracting means 14. A new color map is created based on the k colors used. When (r + k) ≦ m, the color map creating means 15 stores the k colors used in the color image in (m−r) unused entry portions of the color map used in the apparatus. Create a colormap by assigning it. Also,
When (r + k)> m, the number of colors used in the device is (m
−k), and secure k unused entry portions of the color map used by the device, and assign the k colors used in the image to the unused entry portions. create.

The color image reconstructing means 16 recreates image data according to the color map newly created by the color map creating means 15 and displays the image data on the image display means 11.

Next, a processing procedure for creating a new color map in the above-described image processing apparatus will be described with reference to a flowchart of FIG. In this embodiment, an image display unit 11 that can handle 256 colors at the same time is used. In a window system, colors used by the system itself are allocated from the head (index 0) of the color map. .

In step 101, an inquiry is made to the window system to obtain a color map used in the system. Hereinafter, this is referred to as sys_cmap. It is also assumed that the number of colors used at this time is r, and the colors are allocated from entry 0 to (r-1) of the color map.

In step 102, a limited color image file of the application is read. here,
The subroutine shown in FIG. 3 is called to grasp the colors actually used in the image data.

First, at step 201, 25
6 flags (has TRUE or FALSE as value)
(Hereinafter referred to as “used”), and all elements are set to FALSE. Next, step 20
In step 2, information (width, height, resolution, color map, etc.) of the color image is read from the file. Hereinafter, the color map of this image is referred to as org_cmap. In step 203, one line of image data is read from a file and stored in a memory. In step 204, the value of one pixel of the read image data is set to p and used
[P] ← TRUE; This is performed for one line. As a result, the used element corresponding to the color map actually used is set to TRUE. Alternatively, a certain element used [k] is TR
If it is a UE, the element indicated by the index K in the color map is used in the image. In step 205, it is determined whether or not data to be read remains, and the processing is repeated until the processing is completed for all data. After the processing is completed, the process returns to the main routine of FIG.

At step 103 following step 102, a subroutine shown in FIG. 4 is called to create a new color map.

First, in step 301, a table new_cmap for storing a new color map is prepared. In step 302, r data from the top of sys_cmap are copied to new_cmap. That is, i =
For 0, 1, ..., (r-1), new_cmap
[I] ← sys_cmap [i]; Conversion table tran for associating the color map of the image data read in step 303 with a new color map
Prepare a slator. This is a table having 256 integer values, the values of which have not been determined yet. Step 3
04, i ← 255, j = 255, 254,.
For 0, it is determined whether used [j] is TRUE or FALSE.
ew_cmap [i] ← org_cmap [j]; and t
execute the following operation: transformer [j] ← i; tran
The reason why i is substituted for slator [j] is to remember that the element of the color map whose index is j corresponds to the element of the new color map whose index is i. In step 304, used
If [j] is FALSE, do nothing. After the processing is completed, the process returns to the main routine of FIG.

In step 104, a subroutine shown in FIG. 5 is called, and image data is recreated based on the newly created color map.

In step 401, one pixel of the image data is fetched from the memory, and the value of the pixel fetched in step 402 is set as p, and the pixel is called a translator.
Replace with [p]. In step 403, it is determined whether or not data remains in the memory, and the processing is repeated until the processing is completed for all the pixels stored in the memory. After the processing is completed, the process returns to the main routine of FIG.

In step 105, the image data reconstructed by the above-described processing is displayed on the image display means 11.

The extent to which the system use colors (r) are included in the newly created color map is determined by the number of use colors (k) of the image data. FIG. 6 shows the configuration of the newly created color map. FIG. 7A shows the configuration when r + k ≦ 256.
In this case, the color map contains all r used colors of the system, and the remaining space is assigned k used colors of the image data. Therefore, since the colors used in the system and the colors used in the image data can be used as they are, color switching can be avoided. On the other hand, FIG. 2B shows the configuration when r + k> 256. In this case, all the used colors of the image data are assigned, but the number of used colors of the system is reduced to 256-k, so that some used colors are not included. Therefore, color switching occurs for some of the colors, but the colors used in the image data can be used as they are, so that the image quality of the color image can be prevented from lowering.

As is clear from the above-described embodiment, since the processing itself of the image processing apparatus is not complicated, high-speed processing can be realized.

This embodiment is an example for embodying the image processing apparatus according to the present invention, and a similar effect can be obtained by changing or changing the procedure.

[0031]

As described above, in the image processing apparatus according to the present invention, when a new color map is created based on the colors used by the display device and the colors used by the image data, the display of the display device is performed. The colors used in the display device are limited according to the number of colors that can be used, and the colors used in the image data are assigned as they are on the color map. Therefore, it is possible to represent a color image without performing the above operation. Therefore, it is possible to prevent the color switching of the system window as much as possible while preventing the image quality of the color image from deteriorating.

As described above, according to the image processing apparatus of the present invention, it is possible to provide an environment in which the user can operate the apparatus without stress. It is possible to construct a comfortable user interface.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a functional configuration of an image processing apparatus according to an embodiment.

FIG. 2 is a flowchart illustrating a processing procedure when creating a color map.

FIG. 3 is a subroutine showing a processing procedure when reading a file.

FIG. 4 is a subroutine showing a processing procedure when creating a color map.

FIG. 5 is a subroutine showing a processing procedure when reconstructing an image.

FIG. 6 is a diagram showing a configuration of a newly created color map.

FIG. 7 is a diagram showing a configuration of a limited color image.

[Description of Signs] 11 ... Image display means, 12 ... File device, 13 ...
Image reading means, 14 ... Used color extracting means, 15 ...
Color map creation means, 16 ... Image reconstruction means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G06T 1/00 G06T 5/00 G06T 11/00 G09G 5/06

Claims (1)

(57) [Claims] 1. A display means capable of simultaneously displaying a maximum of m (m> 1) limited colors, and converting color image data consisting of n (m ≧ n> 1) limited colors into full colors The first to match
File means for holding the first color map together with the color map, image file reading means for reading the first color map from the file means, and the color image among n colors of the first color map read by the image file reading means Use color extraction means for extracting k (n ≧ k> 0) colors actually used by the data, and associating m limited colors used by the system for display on the display means with full colors Color map creating means for creating a new third color map based on the r colors actually used in the second color map and the k colors extracted by the used color extracting means; Color image reconstruction means for recreating the color image data in accordance with the third color map created by the map creation means Wherein (r + k) ≦ m, the (m−r) unused entry portions of the second color map are used in the color image data. The third color map is created by allocating k colors, and when (r + k)> m, the number of colors used in the second color map is reduced to (m−k) and the second color map is created. And k is reserved for the unused entry portion of the color map, and k colors used in the color image data are assigned to the reserved unused entry portion to create the third color map. Image processing device.