Color Space Conversion For Digital Imaging

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color spaceColor space is the method by which we create, visualize and specify colors. A color is described using three parameters, viz. the human brain uses brightness, the color (red, green and blue) and its intensity to define a color in a color space.

All colors are the result of our perception to a combined effect of variation in the parameters of these basic colors.

There are various color space systems e.g., RGB (red- green- blue), CMY (cyan-magenta- yellow), HSL (hue- saturation- luminance), and YCC (luminance- chrominance) etc. Use of these systems is device dependent, e.g. RGB is used in television, computer etc. while the printer uses CMY system.

Color intensity in digital imaging is coded by data of a set of bits. For each color, 8-bit code is specified per pixel in a 256-level-brightness system (the human eye can differentiate only 200 levels). One can generate 16 million different colors in this system. By increasing number of bits per pixel, more color tones or gray shades can be captured.

Production of a good image depends on many things like illumination during capture, the scanning device and each of them follows different color space system. Therefore, some mathematical manipulation of data is necessary while converting one color space into another.

As RGB system suffers from high information loss and gives 20 bit output per 24 bit data so it is converted to HSL (natural colors) or HSV (value) system (fluorescent colors) to obtain 30-36 bit resolution. In some devices the YCC is also used. The output digital image thus becomes much better in terms of clarity, color and detailing.

The digital imaging experts have formulated algorithms for converting different color spaces from one to another so that the main operant device works on a common color space (to manage the colors of image) where the different spaces of input and output device overlap. An in depth knowledge of color management module (CMM) and colorimetric tools are necessary for best results.

Steps prior to color space conversion in CMM include linearization, to remove effect of gamma correction and collected data are expressed in terms of ‘gamut’ values, next is profiling, i.e. allotting working space and storage format and space to an image for further editing followed by conversion. Color space conversion involves- translation of space data and linking them, mapping gamut for different devices and colorimetric management on the four rendering intents.

CMM is the application software involving embedded algorithms to adjust numeric values when different devices are connected.

Posted in: Digital Imaging

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