Imaging Features > Image Display > Implementing Transparency

Implementing Transparency

You can implement transparency when doing any of the following:

Region processing. Defining a region in an image makes it possible to treat the area outside the region as transparent. The PaintRegion method](../ld/rasterimagepainter-paintregion.html) paints only the region that is defined for an image. The [CombineFastCommand class combines only the area inside the region. You can define a region in a number of ways, including specification of a color. For example, if a transparent color is defined for an image, you can create a region that omits pixels of that color. For details, refer to Creating a Region.

Once a region is defined, you can create a mask from it, using the CreateMaskFromRegion method, which you can save in the alpha channel of a 16-bit or 32-bit file. Refer to the SetAlphaImage method for an example of how to save a region in an alpha channel. When specifying a transparent color, you can use the Windows PALETTEINDEX macro to refer to a particular palette index (where the RasterColor value is >= 0x01000000). Using a palette index for transparency means that one of the remaining colors in the palette can have the same RGB value as the transparent color, without being interpreted as transparent.