Color Spaces

Image color matching uses color spaces to define the set of colors available for a device. To each device context, the system assigns a default color space whose attributes, such as color space type, gamut-matching method and color endpoints, fully define how the system transforms color values for the device. You can create your own color spaces and replace the default color space for a device context by using the CreateColorSpace and SetColorSpace functions. These functions let you explicitly set the format of the color values you use in your application and how the device interprets those values and generates colors.

To create a color space, you set the members of a LOGCOLORSPACE structure and pass the structure to the CreateColorSpace function. You can either set the members to the values you want or specify the filename of a color profile that contains the characterization of the device. For more information, see Color Profiles.

Every color space must have a color space type and a gamut matching method. Gamut matching specifies whether colors in a given image are transformed into an exact match or are modified to make best use of the gamut of the given device, and is described in Gamut Matching Method.

The color space types can be device RGB (red, green, blue), device CMYK (cyan, magenta, yellow, black), or calibrated RGB. Device RGB, the default color space for device contexts, consists of the arbitrary set of colors for the specified output device. Logical color values in this space are given as three 8-bit color values (in a 32-bit value) and are sent to the device driver without transformation. Device CMYK is similar to device RGB except that logical color values are given as four 8-bit values. You use this color space for devices, typically printers, that use CMYK color values. For example, you might use it to carry out color separation and pass color values directly to a CMYK printer.

Calibrated RGB consists of colors in the set defined by three color endpoints. The color endpoints are given as three 32-bit values and are interpreted as defined by the 1931 CIE (Commission Internationale de L'Eclairage) XYZ standard.

After you have created a color space, you can select it into a device context by using the SetColorSpace function. You can delete a color space if you no longer need it by using the DeleteColorSpace function.

You can retrieve the color space for a specified device context by using the GetColorSpace function. This is useful if you want to get the logical definition or color profile file associated with the color space. You can use the GetLogColorSpace function to copy this information to a LOGCOLORSPACE structure.

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