Pixel Format Conversion during Image Saving

ImageGear supports a variety of pixel formats (color spaces and channel depths). However, most image file formats support only a limited set of pixel formats. For example, PNG format does not support CMYK color space, and JPEG Lossy format does not support storing 16-bit per channel pixel values. ImageGear provides conversion from a source image's pixel format into one of the pixel formats supported by the destination image file format.

Availability of a specific pixel format for saving depends on the requested compression, saving options, and filter control parameters.

ImageGear uses the following logic to select the pixel format for saving:

If the format filter directly supports saving of image's pixel format, ImageGear uses this pixel format;
Otherwise, if the format filter supports saving of pixel formats that exceed the image's pixel format (so no image quality degradation occurs), ImageGear uses the one that takes least storage space;
Otherwise, ImageGear uses the pixel format that results in least degradation of image quality.

A special case is when the image color space has to be converted, and multiple choices of channel depths are available. In that case, ImageGear selects channel depths that are equal to the image's channel depths, rather than larger channel depths. This results in a slightly worse quality degradation, but avoids an unexpected increase in image size. For example, PNG format does not support CMYK color space, but it supports storing 8- or 16-bits per channel. ImageGear saves a 32-bit CMYK to PNG as 24-bit RGB rather than 48-bit RGB.

ImageGear does not support conversion from multichannel truecolor color spaces (RGB, CMYK, etc.) into an indexed color space during saving.

Use ImGearSaveOptions.ConversionMode Property to specify the acceptability of image quality degradation or bit depth promotion during saving.

Use ImGearSaveOptions.ForceColorspace Property to make ImageGear use a specific color space for saving.