JPH01181292A - Color picture transmitter - Google Patents

Abstract

PURPOSE:To improve the quality of picture reproduction by dividing a representative color in a color picture into representative color groups, giving a tree hierarchy structure between the representative color groups and applying hierarchical transmission of the color picture according to the hierarchy structure. CONSTITUTION:A picture memory 11 stores a color picture expressed by a number of representative color. A representative color storage section 12 stores a representative color required to display the color picture. Then the number starting from 0 is given to the representative color and the number corresponds to the number stored in the picture memory 11. A characteristic quantity calculation means 13 calculates the quantity of characteristic for each representative color stored in the representative color storage section 12. The hierarchy means 14 divides the representative color into plural representative color groups according to the characteristic quantity and gives the hierarchy structure to the representative color group by repeating the division. A CPU 25 applies various proecessings such as characteristic quantity calculation of the representative color according to a control program stored in a memory 26, hierarchical processing of the representative color, generation of a characteristic color of the representative color group and hierarchical transmission.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a color image displayed on a display device having a frame memory and a color map that outputs RGB values using the contents of the frame memory as an address value. That is, the present invention relates to a color image transmission apparatus that hierarchically transmits a color image in which each pixel has not an RGB value as its pixel value but an address value of a color map, that is, a color number.

[Prior Art] In recent years, image transmission devices have been used for remote monitoring, videophones, and the like. In such image transmission,
It is desirable to be able to determine the content of images to be transmitted at an early stage of transmission, and various hierarchical transmission methods are being considered.The zero-layer transmission method includes: (1) first transmitting images with a small number of #211; (2) a method of first thinning out pixels to transmit an image with low spatial resolution, and then gradually increasing the number of transmitted pixels to obtain an image with high spatial resolution; (3) There is a method that combines the above two methods.・For example, in the case of a black and white image, assuming 8 bits/pixel, the brightness of each pixel is such that a digital value of 0 corresponds to black and 255 corresponds to white, and an almost linear relationship is established between the brightness and digital value. Therefore, by considering the digital value of each pixel as a binary number and transmitting it in order from the bit plane of the most significant bit, it is possible to easily configure a hierarchical image transmission apparatus as described in (1) above. Furthermore, by first thinning out pixels to transmit an image with low spatial resolution, and then gradually increasing the number of pixels to be transmitted to raise the spatial resolution, a hierarchical transmission device as described in (2) above can be easily configured.

On the other hand, in a color image that is displayed with a limited number of representative colors, the pixel value of each pixel or the number of the representative color is used, so a linear relationship like the one shown in L does not hold between the pixel value and the representative color. ,
Therefore, even if the representative color is first transmitted and then the image data is transmitted sequentially from the most significant bit plane as in the case of a monochrome image, it is not possible to reproduce a meaningful image step by step on the receiving side. Therefore, in a color image transmission device that transmits such a color image, hierarchical transmission is possible by first thinning out pixels to transmit an image with a low spatial resolution, and then gradually increasing the spatial resolution. When transmitting pixels, color run length encoding is performed to reduce redundancy.

Figure 5 shows, for example, Journal of the Television Society, Vol. 34.
．． No. 3, pp. 186-193.

19 is a block diagram schematically showing a conventional color image transmission device using color run-length encoding described in ``Trends in 19BOr image file encoding system''.

In FIG. 5, (11) is an image memory, and this image memory (11) stores color images expressed by representative color numbers. (12) is a representative color storage section, and this representative color storage section (12) stores representative colors necessary for displaying a color image. (51) is a run length counting means, and this run length counting means (51) reads each pixel value from the image memory (11) and counts the number of consecutive pixels having the same number. Reference numeral (52) denotes a coded transmission means, which reduces the redundancy of the run length data obtained by the run length counting means (51) by entropy coding or the like and transmits the data.

FIG. 6 shows the format of encoded data transmitted by the above color image transmission device. In the same figure, (I
DI), (ID2) is the representative color number, and (RLI).

FIG. 2 is a specific system configuration diagram of the color image transmission device. In the figure, (21) is a display device, and this display device M (21) includes a frame memory (22), a color map (23), and a display. (24), and the frame memory (22) and color map (23) respectively correspond to the image memory (11) and representative color storage section (12) in FIG. 5 described above. The color map (23) is hardware that generates RGB values using the contents of the frame memory (22) as address values. (25) is a CPU, and this CPU (25) performs run-length encoding according to a control program stored in a memory (26), and transmits encoded data from a communication port (27).

FIG. 7 is an explanatory diagram of hierarchically transmitting encoded data. As shown in the figure, an image is divided into square regions of NxN pixels, and the pixel at position l is first transmitted, and then 2.
By increasing the number of pixels to be transmitted in the manner of 3..., images with progressively higher spatial, resolution, and accuracy can be obtained on the receiving side. This is the run length counting means (51)
This can be achieved by controlling the address value of the pixel read out.

As described above, the conventional color image transmission apparatus transmits representative colors and run-length encoded data.

Furthermore, hierarchical transmission is performed in the form of progressively increasing spatial resolution.

[Problems to be Solved by the Invention] In the conventional color image transmission device as described above, hierarchical transmission in which the spatial resolution gradually increases is possible by thinning out pixels and transmitting them. However, since the value of each pixel is the number of the representative color, and there is no linear relationship between that value and the representative color, hierarchical transmission in which the number of gradations, that is, the types of colors, gradually increases. It is not possible to perform hierarchical transmission in which the spatial resolution and number of gradations gradually increase.

This invention was made to solve the above-mentioned problems, and in the transmission of a color image realized using a limited number of representative colors, that is, a color image whose pixel value is the number of the representative color. It is an object of the present invention to provide a color image transmission device that can perform hierarchical transmission regarding spatial resolution and number of gradations.

[Means for Solving the Problems] A color image transmission device according to the present invention repeatedly divides a representative color into a plurality of representative color groups in order to obtain the feature amount calculated by the feature amount calculation means that calculates the feature amount of one representative color. A hierarchization means that creates a tree-like hierarchical structure between the representative color groups by dividing them, a characteristic color creation means that creates a characteristic color representing the representative color group of each hierarchy, and a characteristic color creation means that creates a characteristic color representing the representative color group of each hierarchy, Hierarchical transmission means for sequentially transmitting hierarchical information created from the characteristic color of the representative color group and the number of the representative color group to which each pixel of the color image belongs, starting from the highest layer of a tree-like hierarchical structure. It is characterized by

[Operation] According to the present invention, the feature amount calculation means calculates the feature amount of the representative color, and the hierarchization means divides the representative color into a plurality of representative color groups according to the calculated feature amount, and repeats this division. This gives a hierarchical structure between these representative color groups. Next, the characteristic color creation means creates a characteristic color representing each representative color group in each layer, and the hierarchical transmission means consists of, for each layer, the characteristic color of that layer and the number of the representative color group to which each pixel belongs. Hierarchical information is created and this hierarchical information is transmitted in order from the highest layer.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram schematically showing a color image transmission apparatus according to an embodiment of the present invention, and FIG. 2 is a detailed system diagram thereof.

In FIG. 1, (11) is an image memory, and this image memory (11) stores color images expressed by representative color numbers. (12) is a representative color storage section, and this representative color storage section (12) stores representative colors necessary for displaying a color image. Here, a number starting from O is given to the representative color, and this number corresponds to the number stored in the image memory (11).

(13) is a feature amount calculation means, and this feature amount calculation means (1
3) calculates the feature amount for each representative color stored in the representative color storage section (12). Possible feature amounts include (a) brightness information L=0.3R+0.59G+O, IIB, (b) color information, (C) frequency of occurrence of representative colors, and a combination of these.

(14) is a hierarchization means, which divides the representative color into a plurality of representative color groups according to the feature amount, and further repeats this division to give a hierarchical structure to the representative color groups. For example, when luminance information is used as a feature, the hierarchization means (14) divides the representative colors into a high-luminance group and a low-luminance group so that each representative color group has the same number of representative colors, and further divides the representative colors into a high-luminance group and a low-luminance group, and then By repeating the division of the groups into high-luminance groups and low-luminance groups, the division continues until each representative color group finally becomes one representative color.

Figure 3 shows the hierarchical structure between the representative color groups in a tree-like manner.
IO, C11) is given. Further, the leaves at the lowest level correspond to the lowest layer, and each representative color group consists of one representative color, which is a characteristic color-representative color (C30 to C37).

For example, in the second layer, representative colors (020 to C23)
is divided into 4 groups, and each representative color group has (0/
l) is given a number. In this way, each representative color group is given a number based on the group division one layer higher.

Next, the characteristic color of each representative color group is created by the characteristic color creation means (1
5). The characteristic color is (a) an arbitrary representative color belonging to each group as the characteristic color.

(b) If the frequency of occurrence of each representative color can be used as a feature amount, select the representative color with the highest frequency of occurrence in each group or the average value of the representative colors as the feature color.

Determined by etc. And hierarchical transmission means (16
) transmits information about each pixel according to the hierarchical structure of representative color groups.

Figure gS4 shows the format of the encoded data transmitted by the hierarchical transmission means (16). That is,
First, for the first layer, the characteristic color of each representative color group and the number of the representative color group to which each pixel belongs, that is, the number given to the tree note, are transmitted, and then the same information is transmitted to the second and third layers. It is transmitted in the order of...

The system configuration diagram in Figure 2 is the same as the conventional example, and the CPU
(25) is stored in the memory (26), and performs various processes such as calculating characteristic values of representative colors, hierarchizing representative color groups, creating characteristic colors of each representative color group, and hierarchically transmitting according to the control program.

In the color image transmission device configured as above,
On the receiving side, when the information on the first layer is received, an image using the characteristic colors of the first layer can be reproduced, and when the information on the lowest layer is received, the same image as on the transmitting side can be reproduced. At this time, on the receiving side, it becomes possible to reproduce images in which the number of colors gradually increases, which was not possible with conventional color image transmission devices. Furthermore, for transmission in which the spatial resolution gradually increases, pixels may be thinned out and transmitted first as in the conventional method, and pixels that have not been transmitted may be sequentially transmitted. This can be easily achieved by controlling the addresses of the pixels read out from the hierarchical transmission means or the image memory. Furthermore, since the information transmitted by the hierarchical transmission means includes redundancy like a normal image, the amount of data can be reduced by encoding processing to remove this redundancy.

[Effects of the Invention] As explained above, according to the present invention, in a color image displayed using a limited number of representative colors, one representative color is divided into representative color groups, and a tree-like pattern is created between the representative color groups. Since a hierarchical structure is provided, there is an effect that it is possible to hierarchically transmit color images desired to have this hierarchical structure, and in particular, to enable image reproduction in which the types of colors gradually increase on the receiving side.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing an outline of a color image transmission device according to an embodiment of the present invention, FIG. 2 is a system configuration diagram thereof, FIG. 3 is a diagram explaining the hierarchical structure of representative color groups, and FIG. 4 is the format of encoded data, MS5 is a block diagram schematically showing a conventional color image transmission device,
FIG. 6 is a diagram explaining the encoded data format of color run length encoding, and FIG. 7 is a diagram explaining the sampling pattern. (13)...Feature amount calculation means, (14)--Hierarchization means, (ts)--Feature color creation means, (16)-
...Hierarchical transmission means. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] (1) In a device that transmits a color image displayed with a limited number of representative colors, a feature amount calculating means that calculates a feature amount of the representative color, and a plurality of representative colors according to the feature amount. A hierarchizing means for creating a tree-like hierarchical structure between representative color groups by repeating dividing into groups and dividing each divided representative color group into a plurality of representative color groups, and each representative color in each layer. A characteristic color creation means for creating a characteristic color representing a group, and hierarchical information consisting of the characteristic color of the representative color group belonging to that layer and the number of the representative color group to which each pixel of the color image belongs for each layer. 1. A color image transmission device comprising: hierarchical transmission means for creating hierarchical information and sequentially transmitting this hierarchical information from the highest layer of a tree-like hierarchical structure.