DE19525177C1 - Simultaneous transmission of still colour graphics image and text - Google Patents

Abstract

The transmission of document test that consists of an RGB picture and text commences with the image being reduced with the air of a colour palette having 256 colours. The reduced image and test is then subjected to a data compression operation followed by transmission. The data is received and processed by a data expansion unit before being relayed for screen display. The process can be adapted to handle information for which there are a number of pictures.

Description

The invention relates to a method according to the preamble of Claim

From US 4 951 132 it is known to scan strung color images and the Store image signals as R-G-B color separations in a memory. The saved Image signals are displayed on a monitor so that a viewer can see one visual color correction for an image sample by manual adjustment of the Color components can perform. The correction setting found is then used for all other images take effect. However, this correction procedure leaves the Correcting the changing image impression or taste of the viewer, whereby a color correction according to the individual requirements of the individual images is not is possible. Rather, the individual images are not individual, but only corrected uniformly according to a subjectively selected image sample.

From US 5 047 842 it is known to reduce the number of colors in a color image to reduce the three primary colors red, green and blue to a total of 256 Mixed color levels (= color palette) can be classified.

DE 40 41 054 A1 discloses a method for transferring templates from an image and a text, which is illustrated with reference to FIG. 1. In order to keep the data capacity for transmission as low as possible, an RGB extract of the image is reduced with a special image compression method and the text with a special data compression method, and the compressed image and text data are combined in a suitable manner. After the transfer has taken place, the data are separated and subjected to a corresponding image and data decompression. If only a limited number of colors can be displayed on the receiver side on the screen, the known method must additionally be reduced to, for example, 256 colors (= color palette) before the image and text can be displayed together on one image.

In the known method, however, there is a very high outlay for the separate Compression of image and text as well as for the separate decompression of image and text required. Furthermore, in the known method Markers are generated to show the spatial associations between image and Ensure text when played back correctly.

In contrast, the object of the invention is to reduce the effort for Reduce compression and decompression of image and text without the Impair the quality of the color images.

The object is achieved by the characterizing features of the Claim specified.

The invention is based on the consideration when there are color-reduced images common data compression method for image data and text data use. Shown multiple color images on the screen at the same time must also have a common color palette for the images in question generated and transferred to the playback page and saved there if necessary. The image-specific color palettes are no longer used for the color reduction, but used the common color palette.

The invention is explained in more detail below with reference to the drawings. Show it:

Figure 1 is a schematic representation of the transmission path for an image and text with different compression methods for image and text data.

Figure is a schematic representation of the transmission path according to an image and text using a compression method for image and text data to the inventive method. 2;

Fig. 3 is a schematic representation of the transmission path for several images and texts with a compression method for image and text data according to the inventive method.

In Fig. 1, the conventional method for transferring templates with an RGB image and text is shown schematically. In order to keep the data capacity for transmission as low as possible, an RGB image is reduced using a special image compression method and the text is reduced using a special data compression method, and the compressed image and text data are combined in a suitable manner. After the transfer has taken place, the data are separated and subjected to a corresponding image and data decompression. If only a limited number of colors can be displayed on the receiver side on the screen, a reduction to, for example, 256 colors must also be carried out before the image and text are displayed together on one screen.

In the method according to the invention shown in FIG. 2, as in FIG. 1, a template with an image in the form of an RGB color separation and text is assumed. In contrast to FIG. 1, the image to be transmitted is already reduced on the transmitter side to a color palette with, for example, 256 colors. The reduced image data together with the text data are then subjected to a data compression process that is optimally designed for this data, and then transmitted. In the receiver, the received data are again subjected to a common decompression procedure and displayed on the screen without additional calculations.

FIG. 3 shows the method according to the invention when several color images with texts are to be displayed together on one screen. A reference palette is generated from a reduced-color reference image, for example image 162 on page 90 of the Broadcasting Communications, special issue 1967, which is either permanently stored in the receiver or which is sent together with the associated image data. For each pixel of the images to be transferred, the individual colors are converted to the values in the reference palette. The converted images and the associated texts are then subjected to a common data compression and transmitted. According to FIG. 2, the received data are decompressed together and displayed without further conversion using the common reference palette.

The following advantages can be achieved with the method according to the invention:

• 1. Since there is no separate image decompression on the receiver side for image data must be performed, and image and text data decompressed together are cheap decoder concepts with little computing effort realizable.
• 2. There is also an (optimal) conversion of the color assignment to the Reference range already on the code side, so that the one necessary in the decoder Computational effort can be reduced further.
• 3. Since no image compression method is used, no defects occur in the picture.  
• 4. The necessary transmission capacity of the method according to the invention is Similar or less than when using common image Compression method (e.g. JPEG).

Claims (1)

Method for the simultaneous display of at least one standing color image and a text on a screen, the color image to be displayed being reduced in the number of its colors in the sense of an image-specific color palette, characterized by the following method steps:

• a) If two or more color images are available, a reference palette is generated from a reference image, which is permanently or temporarily saved on the receiver side,
• b) the color assignment of the pixels of the color-reduced color images is converted from the values of the image-specific color palettes to the values of the reference palette,
• c) the reduced color images are transmitted and reproduced by the recipient using the reference palette;
• d) prior to their transmission, the color-reduced color image or images are subjected to a common data compression with the text;
• e) the received, data-compressed image and text data are subjected to a common data decompression and
• f) the decompressed image and text data are separated, the separated image data being reproduced together with the text using the reference palette stored on the receiver side.