JPS6252680A - Image processor - Google Patents

Abstract

PURPOSE:To obtain a natural display effect by referring to data on a color axis having the largest dynamic range among data on densities and rewriting the density data so as to expand the dynamic range of other color axis in an image memory. CONSTITUTION:According to equations a processor 5 obtains the dynamic ranges DR, DG and DB of three primary colors, and then obtains their averaged density. From the results calculated by the equations, a red color having the largest dynamic range, for instance, and densities with respect to data on dark and light images in respective colors are rewritten. Namely, the red dark and light image data remains unchanged, whereas, with respect to the green dark and light image data, a value obtained from adding a difference between averaged values of the green dark and light image data at a picture element to the red dark and light image data at the picture element is replaced with the green dark and light image data at the picture element. In terms of the blue dark and light image, its replacement is made in the same manner as said green data. Upon the completion of density replacement, a color is rewritten and modified according to the color obtaining the table data of the look-up table 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field> The present invention particularly relates to an image processing device capable of changing color, density, etc. of an image.

<Prior Art> In the past, changing colors has often been done as one of image processing techniques. For example, by changing only the color data of areas corresponding to leaves in a landscape image from green to yellow, a new image with a different flavor from the original image has been generated. In short, for this processing, each of the RED, GREEN, and BLUE data of each image pixel may be replaced with different data. However, if it is attempted to rewrite the data of each image pixel each time the color is changed, the number of accesses from processing hardware such as a CPU to the image memory will naturally increase.

For this reason, color change processing by rewriting the image memory inevitably increases processing time. Therefore, frequent color change processing is unsuitable for systems that require high-speed response, high resolution, or extremely large storage capacity of image memory, and therefore requires specially configured hardware (for example, processors), resulting in complex hardware systems and specialized programming.

Furthermore, in the process of changing the color by rewriting the image memory, once the image data is changed, the original data is erased. Therefore, it is not suitable for a system that often compares the original color and the changed color to IJj, such as color change simulation.

From this point of view, the present inventors created the image processing device described below - fdi2. FIG. 2 shows a partial block diagram of the image processing apparatus.

Reference numeral 1 represents a logical image memory to be described later, and reference numeral 2 represents an image memory that is provided corresponding to R (red), G (green), and B (blue) and stores density information. 3 is a lookup table, and 4 is a D/A converter. The output (video analog signal) of the D/A converter 4 is sent to a CRT for image display.

The lookup table 3 is a type of arithmetic unit, and is composed of a static RAM capable of high-speed signal processing. The data output from the image memory 2 and the logical image memory 1 are combined to form the address signal of the look-up table 3. The capacity of the lookup table 3 is, for example, 256 bytes, and 256 types of information are divided into separate pieces of information (8
bit). However, here, the table data of lookup table 3 is determined so that when the least significant bit of the address signal of lookup table 3 is 1, the data is switched, and when the least significant bit is O, the data is not switched. put.

When image A exists in background B as shown in FIG. 3, if it is desired to change only the color of image A to another color, the following processing is performed.

The data DI is sent to the logical image memo IJ 1 through the processing of the processor 5 shown in FIG. The value of the pixel (pixel) corresponding to the area B which is not changed is stored as 0. On the other hand, the data D2 is sent to the image memory 2 by the processing of the processor 5, and the image memory 2 (capacity of mXnX8 bits when composed of mXn pixels) stores grayscale image data consisting of 7 bits.

Next, as shown in the data flow in FIG. 4, when displaying an image, the value D3 (1 in this case) of the pixel corresponding to the area A whose color is to be changed is stored in the lookup table 3 from the logical image memory 1. is sent, and 7-bit grayscale image data D4 corresponding to the area A is sent from the image memory 2.
When (a7a6a 5a4a3azat) is sent, D4 of the upper 7 bits of lookup table 3 and the lowest 1
The data at the address specified by D3 is c
7c 6c5C4C3C2C11, which is converted into data D5 and sent to the D/A converter 4. On the other hand, the look-up table 3 contains the pixel value D3 corresponding to the area B whose color is not changed from the logical image memory 1.
(0 in this case) is sent from the image memory 2 to the above area B.
7-bit grayscale image data D4 (b7b6b
When 5b4b3b2b1) is sent, the data at the address specified by the upper 7 bits D4 and the least significant bit D3 of lookup table 3 is b7b6b5b.
4b3b2b10 and is converted to this data D5,
This is sent to the D/A converter 4.

As mentioned above, if the contents of the table data of lookup table 3 are adjusted appropriately, the lowest bit of the input address value is 1 or 0, and the contents of the lookup table are referred to differently, so the grayscale image data cannot be changed or changed. Changes can be easily controlled.

Specifically, as shown in No. 51N(a), the table data of lookup table 3 should be formed so that the data exactly the same as the input address value is output regardless of the value of D3 (0 or l). There is no change in color. However, if the table data of lookup table 3 is formed so that data different from the input address value is output according to the value of D3 as shown in 4th [1J(b), only a specific part (here, area A ) color change is performed. That is, the brightness of area A is improved by lifting only the data at odd addresses. This processing is a kind of emphasis processing, but by switching the table data of the lookup table 3, other processing such as binarization and 2-inversion of the shading of the area A can also be executed.

However, when changing the color as described above, if the original color of the area where the color change is being made is close to a pure color, for example, if you want to change to a color that is complementary to that color, a good display color may be used. The problem is that it cannot be realized. In other words, in the case of an image with shadows, the color becomes flat, with most of the shadows producing the image. The reason for this is as follows.

If the original color is close to a pure color (for example, red), the density change of the red color will be very large if there is a shadow in the image, and therefore the dynamic range of the red color will be large. Therefore, it is possible to obtain subtle changes in shading. However, if we focus on the blue component in the same image, it is close to the pure color of red, so there is very little change in the density of blue.

Therefore, the dynamic range of blue is small. Here, in order to change the color of the image to blue, the output of the red lookup table is reduced and the output of the blue lookup table is expanded, and the color of the image changes to blue. However, as mentioned above, the dynamic range of blue is small, so subtle changes in shading cannot be obtained.
- <Purpose> The present invention has been made in view of the above points, and provides a system that can quickly change the partial color of an image, and also maintains natural shading when changing the color. The purpose is to provide a device that can.

<Embodiment> Hereinafter, an embodiment of an image processing apparatus according to the present invention will be described in detail using the drawings.

Next, a step-by-step explanation will be given of arithmetic processing for gray scale image data of each of the three primary colors R, G, and B stored in the image memory 2. The basic device configuration is as shown in FIG.

1) Step 1 The processor 5 calculates the dynamic ranges DR, DG, and DB of the three primary colors.

In the equation (+), 12g and b are the grayscale image data of the three primary colors at each pixel, and the calculation is performed by extracting the image data over the entire range of the image.

11) Step 2 The processor 5 calculates the density average of each of the three primary colors.

In formula (2), <r>, <cr>, <b>
is the density average value of each color, and n is the number of pixels.

iii) Step 3 Based on the calculation result of the fi1 formula, assuming that the color with the largest dynamic range, red in this case, is the color, the processor 5 performs the following calculation on the grayscale image data of each pixel.

In Equation (3), for red shading image data, the original data remains unchanged, and for green shading image data, the red shading image data at that pixel is changed to the green shading at that pixel. The value obtained by adding the difference from the average value of the image data is replaced with the green gradation image data at that pixel, and for blue gradation image data, the blue gradation image data at that pixel is added to the red gradation image data at that pixel. The value obtained by adding the difference between the average value of the grayscale image data and the average value of the grayscale image data is replaced with the blue grayscale image data at that pixel. However, the data after calculation r g−<cr>
Since it is impossible to display when is a negative value, let q=0 and r
When +b-<b> is a negative value, it is impossible to display it, so b
=0.

The above calculation was for the case of DR>DG, DB, but DG
>DR, DB, r=g+r <r> 1 is used, and when DB>DR, DG, the grayscale image data can be switched using the following formula.

1) Step 4 With the grayscale image data in the image memory switched in Step 3, the color is changed by rewriting the table data in the lookup table 3 according to the desired color.

Effects> According to the present invention described above, a sufficient dynamic range can be obtained in any direction of the color axes of the three primary colors, so that a natural display effect can be obtained. Therefore, color changes using lookup tables can be performed more effectively by simple calculations.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing density data distribution of each color in color space, FIG. 2 is a partial block configuration diagram of an embodiment of an image processing apparatus according to the present invention, FIG. 3 is an explanatory diagram of an image, The figure is an explanatory diagram of the data flow, and FIG. 5 is a characteristic diagram of the lookup table. In the figure, 1: Logical image memory 2° Image memory % IJ 3° Lookup table 4: D/A converter 5' Processor
6: Main memory 7: Latch circuit 8: Gate agent Patent attorney Aihiko Fukushi (and 2 others) and σ
(b
) Figure l: $2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. An image memory that stores density data of each pixel constituting an image; a logical image memory that stores data that determines a pixel corresponding to an area where the density data is to be changed; and the image memory. and a look-up table that is introduced by the output data of the logical image memory and rewrites and sets the density data of the pixels corresponding to the area where the density data is to be changed, and data on the color axis having the largest dynamic range of density data. and a display means for displaying an image based on the output of the lookup table. Processing equipment.