JP2981292B2 - Image display method and apparatus - 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 display method and apparatus for an image display device using a color map.

[0002]

2. Description of the Related Art A color display is widely used as an output device of a computer. However, a full-color display capable of simultaneously displaying all displayable colors is generally expensive.
Register only some of the displayable colors in the color map,
In many cases, a color display that can simultaneously display only those colors is used. This is called a color map type color display.

FIG. 4 is a block diagram for explaining the general configuration of a conventional color map type color display. In the figure,
1 is a collating unit, 2 is a color map, and 3 is a display. This collation selected with the collation unit 1 from the registered the closest color to the original color in the color map 2 for each pixel of the image data 4 to be input in the collating unit 1 color, it on the display 3 indicate. Therefore, the number of colors that can be displayed simultaneously is limited to the size of the color map 2, and red (R), green (G), and blue (B) are each represented by 8-bit gradation and 256 colors can be registered in the color map. When a taken as an example, simultaneously displayable colors are only 256 colors out of 2 ²⁴ colors.

In such an image display method, image data 4 to be displayed is smaller than the number of entries in the color map.
When many colors are used in the image, it is impossible to display the original color of the image as it is, a color different from the original color of the image is displayed, or the color changes continuously. False contours may occur in the part where there is.

[0005] Therefore, various studies have hitherto been made on a method of creating a color map which can obtain a display image as faithful as possible to the original image. One such color map creation method is to create a color map based on the color distribution of pixels included in an image to be displayed.
(Reference: Watanabe, "High-speed Algorithm for Approximately Displaying 256 Colors of Color Image", IEICE D,
Vol. J70-D, No. 4, pp. 720-726, April 1987).

In this method, first, a distribution in a color space of pixels included in an image to be displayed is obtained. Next, a representative color is sampled densely in a color region where the pixel distribution is dense, and sparsely sampled in a color region where the pixel distribution is sparse. Then, the sampled representative colors are registered in the color map. When this method is compared with a method in which the representative colors are sampled uniformly in the color space, the error increases with respect to the infrequent colors, but the colors can be reproduced more faithfully with the frequent colors. Higher quality images are obtained than with the uniform sampling method. As described above, in this method, since a color map is created according to an image, it is possible to suppress deterioration in quality of an arbitrary image.

[0007]

However, in the above-described conventional method, a color map is created by calculating the color distribution of an image each time an image is displayed. There is a problem that processing time is required in comparison.

On the other hand, depending on the application of the image display device, it may be sufficient if a high quality image can be obtained for a specific type of image. In this case, a color map adapted to an arbitrary image is created. No need. In particular, when a color image is used as the main information of an image, such as when a color display is used as a display unit for a videophone or video conference, it is important to obtain a high-quality image of the image. High quality is not required for images. Therefore, in such a case, it is not necessary to be able to display all the images with high quality by using a conventional method that requires a long processing time.

Further, when displaying a human image, it is important that a human body part is displayed with higher quality than a background part. However, in the conventional method, the representative color is simply sampled densely in a color region where the pixel distribution is dense, and sparsely sampled in the color region where the pixel distribution is sparse. Therefore, there is a possibility that a large number of representative colors are assigned to the background color portion. When many representative colors are assigned to the background color in this manner, the number of representative colors assigned to the human body part relatively decreases, and the image quality of the human body part, which is the main information of the image, deteriorates.

The image of the main information is not limited to the human body part. For example, an animal in a zoo or a car in a car race is an image of the main information, and high quality image display is required. .

By the way, looking at the image of the main information about the human body part, it is usually important that the human body part such as skin and hair is faithfully displayed in the human image, and the background part is slightly deteriorated in quality. Is acceptable. Therefore,
As for a human image, the quality of an image can be maintained by using a color map created by sampling representative colors densely near the human body color such as skin and hair, and sparsely sampling other portions. On the other hand, when this color map is used for an image other than a human image, an error between a color that does not exist in the human body and a display color increases, and the quality deteriorates.

The present invention solves these problems described above,
It is an object of the present invention to provide an image display method which is faster than a conventional image display method and in which an image of main information is displayed with higher quality than other images.

[0013]

According to the present invention, there is provided a color map in which colors that can be simultaneously displayed on a screen are registered, and a color closest to the color of the pixel is referred to in the color map with reference to the color map for each pixel. In the method of displaying an image by selecting from registered colors and displaying the color instead of the original color of the pixel, the color of the image of the main information is relatively smaller than the other colors. Using a color map for main information configured so that the scale is fine and a general color map configured so that the scale is uniform for all colors,
It is determined whether or not the image to be displayed is the image of the main information, and the image determined to be the image of the main information is searched for the closest representative color using the main information color map, and Is displayed, and an image determined to be not an image of main information is searched for the closest representative color using the general color map, and the representative color is displayed.

[0014]

According to the present invention, for example, when the image of the main information is a human image, first, the representative colors are densely set in the color area near the human body color such as skin color and hair color. Second, general colors composed of representative colors obtained by uniformly sampling a color space using a color map for a person image obtained by sampling and representatively sampling representative colors for other color regions. Using the map, it is further determined whether or not the image to be displayed is a person image, and when it is determined that the image is a person image, the image is displayed using the color map for the person image. Is determined, the image is displayed using the general color map.

As described above, in the color map for a human image, since representative colors are densely sampled with respect to the skin and hair of a human body, when a human image is displayed using this color map, the skin and hair portions are displayed. Can reduce the error between the primary color and the display color, and can display the human body part, which is the main information of the human image, with high quality.

On the other hand, since the general color map uses representative colors obtained by uniformly sampling a color space, when an image is displayed using this color map, the quality of a specific color is degraded. And the same error can be displayed for any color.

Since the color map for the person image and the color map for the general purpose are used by switching depending on whether or not the image is a person image, the human body can be displayed faithfully with respect to the person image. Can be displayed using a general-purpose color map so that each color has the same error.

In displaying an image, a color map for a person image and a color map for a general image prepared in advance are used, so that the image can be displayed at a higher speed than the conventional method.

[0019]

In this embodiment, the original image is represented by 2 ²⁴ colors of 8 bits each for R, G and B, and 256 colors registered in the color map out of 2 ²⁴ colors can be displayed simultaneously. The following description will be made by taking as an example the case where the gradation of the original image is different, the color expression other than RGB is used, or the number of colors that can be registered in the color map is different.

FIG. 1 is a block diagram of an example of a system configuration embodying the present invention. In the figure, reference numeral 1 denotes a collating unit, 2A denotes a color map for a human image, 2B denotes a general color map, 3 denotes a display, and 5 denotes a judgment. The unit 6 is a color map switching unit.

The color map 2 for a person image shown in FIG.
A is a color map created by finely sampling representative colors for the human body color such as skin and hair.

FIG. 2 is an example of a processing flow for creating the color map 2A for a person image. First, the skin and hair parts other than the clothes and background are cut out from the person ( step 1 ).
A point is plotted at a corresponding position in the RGB space for each pixel of the cut-out portion ( step 2 ). That is, for example, the RGB value of a certain image is R = 10
If 0, G = 200 and B = 200, the point (100, 200, 200) is plotted in the RGB space.
Such extraction and plotting are performed for a plurality of different human images ( step 3 ).

Next, the RGB space, the density of the plotted points is divided into areas S ₂ the other a region S ₁ which is equal to or greater than a predetermined threshold value (Step 4). And the area S
₁ is divided into _部分 partial areas ( step 5 ). The center point of each partial area is set as a representative color ( step 7 ).

Further, by dividing the area _{S 2} 256-to _χ number of partial areas (step 6), is referred to as representative color center point of the partial regions (step 7). However, _chi as the volume ratio of the area _{S 1} and the area _{S 2 γ,} χ> 256 × to satisfy the _gamma. The person image color map 2A is composed of 256 representative colors sampled in this manner.

The general color map 2B is a color map created by uniformly sampling representative colors in the RGB space.

FIG. 3 is an example of a flow of a process for creating the general color map 2B. First, the RGB space is 256
It is divided into a plurality of partial areas ( step 1 ). This division is performed so that the space is divided as evenly as possible.
Then, the center point of each partial area is set as the representative color ( step
2 ). The general color map 2B is composed of these 256 representative colors.

Next, the operation of the system shown in FIG. 1 will be described. When the image data 4 is input, the determination unit 5 determines whether or not the image to be displayed is a human image. As a determination method, there is a method of determining whether or not the image is a human image using an image recognition device, a method of assigning an identifier indicating whether or not the image is a human image at the time of creating image data, and determining the image based on the identifier.

The collating unit 1 searches for a representative color closest to the original color of the pixel with reference to the color map, and displays the representative color on the display 3. That is, the color map is displayed using the color map for human image 2A by the color map switching unit 6 when the image is determined to be a human image by the determination unit 5, and by using the general color map 2B when it is determined to be not a human image. 3 is displayed at high speed.

The above description has been made by taking a person image as an example of the main information, but as described above, animals in a zoo, cars in a car race, and the like also use individual color maps, respectively, and are distinguished from general color maps. Thereby, the same image display effect can be obtained.

[0030]

As described above, according to the image display method and apparatus of the present invention, since a predetermined color map is used, a color distribution is obtained for each image and a conventional color map is created. Images can be displayed at high speed. In addition, for the image of the main information, for example, a human image, a color map in which the color portion of the human body is finely sampled is used.

[Brief description of the drawings]

FIG. 1 is a block diagram of an example of a system configuration for implementing the present invention.

FIG. 2 is a diagram showing a processing flow for creating a color map for a person image used in the present invention.

FIG. 3 is a diagram showing a processing flow for creating a general color map used in the present invention.

FIG. 4 is a block diagram illustrating an outline of a configuration of a conventional color map display.

[Explanation of symbols]

1 collation unit 2A color map for human image 2B
General color map, 3 display, 4 image data, 5 determination unit, 6 color map switching unit.

Continuation of the front page (56) References JP-A-59-123390 (JP, A) JP-A-60-91770 (JP, A) JP-A-60-220660 (JP, A) JP-A-62-84386 (JP) JP-A-62-281067 (JP, A) JP-A-63-303339 (JP, A) JP-A-63-312151 (JP, A) JP-A-64-17042 (JP, A) 1-176560 (JP, A) JP-A-2-96477 (JP, A) JP-A-3-135290 (JP, A) JP-A-3-182192 (JP, A) JP-A-4-270474 (JP, A) A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G09G 1/00 G09G 3/20 G09G 5/00 G06F 15/62 H04N 5/00

Claims (2)

(57) [Claims] 1. A color map in which colors that can be simultaneously displayed on a screen are registered, and a color closest to a pixel color is selected for each pixel from the colors registered in the color map with reference to the color map. In the method of displaying an image by displaying the color in place of the original color of the pixel, the color of the image of the main information is pre- configured so that the color increment is relatively small compared to other colors. Using the color map for main information and the general color map configured in advance so that all colors are equally spaced, it is determined whether the image to be displayed is the image of the main information or not. If it is determined to be a picture, the entire display image
With respect to the main information color map, the closest representative color is searched for and the representative color is displayed , and when it is determined that the main information is not an image, the general color map is used for the entire display image. An image display method for searching for a near representative color and displaying the representative color. 2. A judging section that judges whether an image of the image the main information to be displayed, an important color for key information
As for the colors, the color notch is relatively small compared to other colors
Color map for main information pre-configured ,
Pre-configure so that all colors are evenly spaced
The general-purpose color map generated and the main information
Switch between the two color maps when determined to be an image
Color map switching unit, and color map switching unit
Refer to the color map validated by
Search for the representative color closest to the color of
An image display device comprising: a collation unit for displaying the image in (a); and a display for displaying an image.