ImageGear for C and C++ on Windows v19.3 - Updated
Extra Channels Supported
Alpha channel defines opacity/transparency of an image. Only one Alpha channel per image can exist. A color space with an Alpha channel can be pre-multiplied or non-pre-multiplied. This is the common definition of an Alpha channel, used by most file formats, such as TIFF, PNG, SGI, TGA, etc.
Extra channel is any channel besides regular color channels or Alpha. There can be any number of Extra channels per image. Extra channels may have some defined semantics, such as Mask or Spot channels, or can be "Unknown", meaning that ImageGear does not know how to display or process them. See the following sub-sections for more information:
Mask channel specifies a mask or selection in the image. There can be any number of mask channels per image. Images are never pre-multiplied by mask channels. In ImageGear, Mask channel is a subtype of Extra channel.
Spot channel uses a specific color. The color can be specified using a standard color space, such as RGB or CMYK, or using a custom color, such as Pantone, TRUMATCH, etc. The custom spot color is defined by its Vendor ID and Color ID.
Existing Vendor IDs:
In ImageGear, Spot channel is a subtype of Extra channel.
Unknown channel is an additional channel whose purpose is unknown to ImageGear. In ImageGear, Unknown channel is a subtype of Extra channel.