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Tile based color space transformation

IP.com Disclosure Number: IPCOM000237921D
Publication Date: 2014-Jul-21
Document File: 3 page(s) / 113K

Publishing Venue

The IP.com Prior Art Database

Abstract

Color space transformation using tetrahedral interpolation is one of the more computationally expensive functions in the color image path for digital copiers and Multifunction Devices (MFD’s). In a software based image path, it is desirable to speed up the color space transformation function to improve the system performance. This proposal describes a method to reduce the amount of computation needed for color space transformation. The idea can be used in converting an image from CIELab to CMYK. It can also be used in other conversions such as from CIELab to YCbCr. Specifically, the color space transformation method is selected on a tile-by-tile basis. For tiles detected as having color content, regular tetrahedral interpolation is performed; for tiles detected as neutral, a simple L* to CMYK table look-up is performed. The proposed method fits nicely into the tile-based processing framework in a software based image path. There is no extra overhead in tile-based neutral detection as that’s a needed step in page-level neutral/color detection. For pages with a limited amount of color, the saving in computation time is very significant with the proposed method.

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Tile based color space transformation

Color space transformation using tetrahedral interpolation is one of the more computationally expensive functions in the color image path for digital copiers and Multifunction Devices (MFD’s). In a software based image path, it is desirable to speed up the color space transformation function to improve the system performance.  This proposal describes a method to reduce the amount of computation needed for color space transformation.  The idea can be used in converting an image from CIELab to CMYK. It can also be used in other conversions such as from CIELab to YCbCr. Specifically, the color space transformation method is selected on a tile-by-tile basis.  For tiles detected as having color content, regular tetrahedral interpolation is performed; for tiles detected as neutral, a simple L* to CMYK table look-up is performed. The proposed method fits nicely into the tile-based processing framework in a software based image path. There is no extra overhead in tile-based neutral detection as that’s a needed step in page-level neutral/color detection. For pages with a limited amount of color, the saving in computation time is very significant with the proposed method.

Figure 1 shows an example of a software based image path with tile based Lab to CMYK conversion.

Figure 1. System level image path diagram with tile-based Lab to CMYK Conversion

In the example illustrated in Figure 1, the image-signal processor, which is a DSP type of component that can be found in some SoC (System on a Chip) processors, is used to perform the conversion from RGB to Lab one tile at a time. The image-signal processor can also detect and report if a tile is neutral or it contains color content. The conversion f...