JPS62261293A - Image data converting method - Google Patents

Abstract

PURPOSE:To form the best image with a very small number of the color for a videotex by executing the replacement to temporary representative color color-coordinates based on an appearance frequency standard and a space Euclidean distance after image data for printing are converted to an RGB data. CONSTITUTION:RGB data are matched to a videotex and converted to the 4-bit data of respective colors. Next, a histogram is prepared in an RGB space for the RGB data of the 4-bit of respective colors, and close color coordinates are absorbed and unified in the RGB space in the sequence from the color coordinates with high frequency. Concerning the RGB data after unification, classification is executed in the sequence of the appearance frequency again and the high order NXK number of color coordinates are made into a temporary representative color. The color coordinates of the lower order than this are replaced to the NXK number of the color coordinates having the smallest L*U*V* space Euclidean distance. The designated color coordinates are selected to the representative color unconditionally and other color coordinates are automatically converted. The number of the designated color is smaller than N.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to converting image data for printing into data for videotex, and converting it into data with a limited number of colors of 1111. Regarding how to.

(Prior art and problems to be solved by the invention) In recent years, the use of videotex systems has rapidly spread. In Japan, the CAPTAIN system has been developed mainly by NTT, and in North America and other countries, the NAPLPS system has been developed. This Videotex system is characterized by the ability to exchange not only text information but also image information, but since image information cannot be transmitted by simple encoding like text information, each method uses They have their own methods for handling information and impose their own restrictions. Therefore, at present, CAP
There is no compatibility between TAIN system images and NAPLPS system or other Videotex system images. Since there is no compatibility even within the same Videotex system, there is also no compatibility between images produced by the various computer systems (including personal computers) that are currently available.

Therefore, conventionally, to create image information of the CAPTAIN method, an image input device dedicated to the CAPTAIN method was required, and to create image information of another method, another dedicated image input device was required. Ta. These dedicated image input devices are quite expensive, and require a lot of labor and time to input one image. For example, for general input work, first, use the camera or C
It is necessary to take a method of importing line drawings using OD skits, etc., or inputting them directly from a tablet, and then coloring them while referring to the monitor screen.

Regarding this coloring, there are various restrictions depending on the method, and the procedure is such that a designer prepares a coloring instruction sheet that meets these restrictions in advance, and an operator performs coloring based on this. This coloring work requires a lot of effort and time. Furthermore, even if a designer creates an image using a personal computer, etc., the handling of image information is different in each Videotex system, and there are also restrictions on scale, so in the end, this image cannot be used with a camera or COD scanner, etc. After importing, new coloring must be performed.

Therefore, in recent years, attempts have been made to convert arbitrary image information into image information that conforms to the standards of a predetermined Videotex system. However, as mentioned above, each method of the Videotex system incorporates its own method for handling image information and imposes its own restrictions. One constraint on converting arbitrary image information to a given Videotex system standard is the limited number of colors. For example, in the CAPTAIN method, one pixel is limited to 16 colors in systems with rank 2 or lower, and can be any one color in systems with rank 3 or higher.
It must be expressed in six colors. Therefore, it has been a big problem how to deal with this limitation in the number of colors when performing conversion.

Therefore, the present invention provides an image data conversion method that copes with the limitation on the number of colors required by a predetermined video ax system standard and can easily convert arbitrary image data into image data that conforms to the above standard. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, the present invention obtains RGB data by performing complementary color conversion on C1M and Y data for printing, and converts this RGB data into a Videotex color space quantization level. Together, they are expanded in the RGB space to create an appearance frequency table, absorbing the adjacent color coordinates in order of the highest appearance frequency, then create an appearance frequency table again, and select colors with a culm degree that is 2 to 4 times the number of representative colors N, in order of the highest appearance frequency. The color coordinates are used as a temporary representative color, and the color coordinates below are
'''After replacing the color coordinates with the color coordinates of the provisional representative color with the smallest V* spatial Euclidean distance, create an appearance frequency table again and use the top N color coordinates as representative colors in descending order of appearance frequency.
The 8 colors below are replaced with the top N color coordinates with the smallest L"U"■* spatial Euclidean distance to obtain image data with the number of colors for Videotex.

Further, after determining the temporary representative color, by specifying one or more color coordinates therein, a drawing method deck including the specified color in the representative colors is obtained.

(Embodiments of the Invention) An apparatus for performing processing according to the present invention will be explained with reference to FIG. 2, an image data processing procedure thereof will be explained with reference to FIG. 3, and then a color number determination according to the present invention will be explained with reference to FIG. .

First, as shown in FIG.
A color display DP and a floppy disk FD, disk DK, and tape MT as SAI devices are connected via a bus, and a C
G production equipment CG.

Personal computer PC1 captain information input mci.

A NAPLPS information input machine Nl, a layout scanner system LSS, etc. are combined.

In this device, processing as shown in FIG. 3 is performed.

First, in step 811, printing image data, such as CMYBl data, which is obtained by adding a smear process to cyan, magenta, and yellow color separation data captured from a document image using a layout scanner, is prepared. This CMYB1 data is converted to RGB data (step 513).

Since the final image is for videotex, this is done by a simple method of taking complementary colors.

Thereafter, in step 13, pixel density conversion and trimming processing are performed. This is for the purpose of data compression. In the case of printing image data, taking A4 size decomposed version data as an example, it is about 9 million drawings, which is about 50 times more data than Videotex, for example, Captain (Rank 3). Furthermore, due to the characteristics of layout scanners, when displayed on a display, the entire screen becomes glarey, so measures must be taken to prevent this.

Therefore, the data J is reduced by averaging the inter-pixel deviation of the RGB data obtained in step 812.

If a computer graphic image is prepared in step S13 (821), the image data is RGB data, so the process in step 813 is immediately performed without going through step 312.

Next, in step 814, layout processing is performed. This is a process that masks parts other than image data.
Taking the case of the captain system as an example, "i-Lance Parent" is specified.

Thereafter, in step 815, color number processing is performed.

This is the central processing of the present invention, and the details will be described later, but it is used in Videotex to process image data in accordance with the number of colors.

Subsequently, in step 816, colored block processing is performed. Taking the captain system as an example, 2 colors within 4 x 4 pixels (
It is expressed by colored blocks called the previous day's color and background color.

Therefore, in order to convert into a captain image, the image data that has been subjected to color number processing is divided into blue block units, and inappropriately colored blocks are corrected. Here, L-ranked two colors are selected based on the pixel frequency within the block, and for the third and subsequent colors, surrounding pixels are looked at and converted to whichever of the two colors is more common.

Then, in step 817, format conversion processing is performed. This is the captain PL in the case of the captain system.
Convert to photographic screen code according to PS. Also, for arbitrary color screens, an LUT (look-up table) is set in advance. Note that step S22
Screen management information (A information), character screen information (B information), connection screen information (C information), melody screen information and Can be merged.

As a result of the above, the captain screen is completed (step 518).
).

Next, step 815 in FIG. 3, that is, color number processing, will be explained in detail with reference to FIG.

The print image data is expressed in 8 bits each for RG8. Nll for this image data! ] The idea behind selecting representative colors is to distribute them as evenly as possible within the color space.
There are two methods: a method of selecting a representative color according to the pixel density of the color Ij region, and a method of selecting a representative color according to the pixel density of the color Ij region.

In the case of the captain, N=15 and the number of colors is extremely limited, resulting in a coloring book-like expression. In this case, it is better to select representative colors according to the distribution density of the colors than to select representative colors in a distributed manner to preserve the information of the original image. However, because the color distribution density is low, important colors are missing in the screen configuration.

As a countermeasure for this, we have made it possible to specify a specific color to be saved once the number of colors has been reduced to a certain degree.

The color number processing procedure of the present invention is as shown in FIG. First, step S1 corresponds to step S14 in FIG. 3, in which 8-bit RGBli@ data for each area is prepared. This RGB data is converted into 4-bit data for each color in accordance with the videotex in step S2. Various methods can be used for this conversion method. A histogram is created in the RGB space for the 4-bit RGB data for each color obtained thereby, and the data is classified in descending order of appearance frequency (step 83).

Based on this classification result, in step S4, the color coordinates with the highest frequency of appearance are selected in the RGB space by, for example, ±1 or ±2.
Absorb and integrate adjacent color coordinates in a range of pixels. The RGB data after this integration is classified again in order of appearance frequency, and the top NXK color coordinates are set as temporary representative colors (K=2 to 4).

Color coordinates lower than this are replaced with the NXK color coordinates having the smallest L*U''V'' spatial Euclidean distance (step S5).

The image thus obtained is displayed on a display and viewed by an operator. For colors that are important in the double-sided configuration but appear less frequently, the position of the color on the screen is designated with a cursor. This is the color specification in step S7. The specified color coordinates are unconditionally selected as the representative color, and other color coordinates are automatically converted. The number of designated colors is less than N.

When the necessary color designation is completed, a representative color is extracted in step S8. In this case, each color coordinate is classified in order of frequency of appearance, and the top N color coordinates are extracted as representative colors. As in step S5, the color coordinates with a lower rank are L“u”
“v” spatial Euclidean distance! Top N with smallest distance
Replaced with color coordinates.

The image data thus obtained is processed in steps 316 and 317 in FIG. 3 to become videotex image data.

(Effects of the Invention) As described above, the present invention converts printing image data into RGB data, compresses the data based on appearance frequency, and selects temporary color coordinates that are approximately 2 to 4 times the final number of colors. Other color coordinates are changed to temporary color coordinates based on the L'U''V'' spatial Euclidean distance, and then the upper color coordinates corresponding to the final number of colors are used as the representative color, and the color coordinates are changed again to Videotex. For f! ! , because we obtained several image data,
Data processing can be performed closer to human color perception than when all color processing is performed in RGB space. Because you can specify the color once you have decided on the temporary representative color,
The best image can be formed with a very small number of colors for videotex.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the procedure of color number processing according to the present invention, FIG. 2 is an explanatory diagram showing the configuration of an image processing apparatus according to the present invention, and FIG. It is diyat. COM...Computer, C8...Console, O
P...display, FD...floppy disk, DK...disk, M...tape. Applicant's agent Sato-Omomo 2 Figure 31 yen] Tesho Cne 11 Orthography (Method)) August 5, 1961

Claims (1)

[Claims] 1. Expand RGB data in RGB space according to the videotex color space quantization level to create an appearance frequency table, absorb color coordinates that are close to each other in descending order of appearance frequency, and then calculate the appearance frequency. Make a table and rank the representative colors N from 2 to 4 in order of frequency of appearance.
The upper color coordinates that are twice as high are set as temporary representative colors, and the other lower color coordinates are replaced with color coordinates in L^*U^*V^* space, absorbed into the temporary representative colors by distance calculation, and then an appearance frequency table is created. The top N color coordinates in order of frequency of appearance are used as representative colors, and the other lower color coordinates are replaced with color coordinates in L^*U^*V^* space and absorbed into the representative color by distance calculation to become representative colors. An image data conversion method for obtaining videotex color image data expressed by N colors. 2. Develop the RGB data into the RGB space according to the videotex color space quantization level, create an appearance frequency table, absorb color coordinates that are close to each other in order of appearance frequency, then create an appearance frequency table and sort them in descending order of appearance frequency. The upper color coordinates of approximately 2 to 4 times the number of representative colors N are set as temporary representative colors, and at least one color coordinate of this temporary representative color is selected as the specified color according to the specified input, and other lower color temporary coordinates are selected. Replaces the color coordinates in L^*U^*V^* space, absorbs them into the temporary representative color by distance calculation, and creates an appearance frequency table and selects the top N color coordinates that include the specified color in descending order of appearance frequency as the representative color. Then, the mark containing the specified color in other lower color coordinates is replaced with color coordinates in L^*U^*V^* space and absorbed into the representative color by distance calculation, resulting in a video expressed by the number of representative colors N. An image data conversion method that obtains image data with the number of colors for Tex.