When you move or copy a selection, some of the pixels surrounding the border are included, especially when the selection is anti-aliased or feathered. Matting cleans up the border by removing these pixels.
There are three Matting commands: Remove Black Matte, Remove White Matte, and Defringe. Use the Remove Black Matte or Remove White Matte command when the selection is from an image with a black or white background. These commands remove the black or white pixels at the selection edges.
Use the Defringe command when the selection is from an image with a colored background. Defringing bleeds non-feathered pixels in the selection edges outward and over the “jaggies” in the feathered part of the selection.
Important: This command works on 16 million color and greyscale images only. To increase the color depth of an image, see Increasing the Color Depth of an Image.
To use a Matting command:
If the selection is not floating, choose Selections > Float.
Do one of the following:
To remove the black matte, choose Layers > Matting > Remove Black Matte.
To remove the white matte, choose Layers > Matting > Remove White Matte.
To move a colored matte, choose Layers > Matting > Defringe. The Defringe dialog opens. Enter the number of pixels to defringe and click OK.
Adding or Removing a Color from a Selection
Changing the Feathering of a Selection
Modifying the Select Selection Borders