This is documentation for Mathematica 8, which was
based on an earlier version of the Wolfram Language.

# ImageCompose

 ImageComposegives the result of overlaying overlay onto image. ImageComposegives the result of alpha blending overlay into image using blending fraction . ImageComposeplaces the center of overlay at position pos in image. ImageComposeplaces the point opos in overlay at position pos in image. ImageComposeuses the compositing fractions and the specified compositing mode.
• ImageCompose always gives an image with the same pixel size as image.
• ImageCompose does alpha blending if obj has an alpha channel.
• ImageCompose effectively sets the alpha value for obj to , or multiplies an existing alpha channel by .
• ImageCompose overlays obj pixel-by-pixel onto image, without changing the size of obj.
• The object obj can be either an explicit image object, or a graphics object that is automatically rasterized to have the same image size as image.
• The position pos in image, or the position opos in obj can be specified in the following ways:
 {x,y} absolute pixel offset from the bottom-left corner Scaled[{sx,sy}] scaled position from 0 to 1 across the object {posx,posy} named and positions
• If only one of and is given, the other is assumed to be Center.
• The pixel offsets can be negative, indicating a point outside of image or obj.
• ImageCompose yields an image with an alpha channel only if image has an alpha channel.
• ImageCompose effectively adds an alpha channel with value to image.
• ImageCompose combines a fraction of every pixel value in image with a fraction of every pixel value in obj, in all cases taking account of alpha channels.
• With value for mode, obj is treated as on top of image. With value it is treated as underneath. And with value , image and obj are treated symmetrically.
• The following choices of correspond to standard Duff-Porter compositing operators:
 {1,1,1} object "over" image (default) {0,1,1} object "atop" image {1,0,1} object {0,0,1} object "in" image {1,1,0} "xor" operation {0,1,0} image "out" object {1,0,0} object "out" image {0,0,0} "clear" image {1,1,-1} image "over" object {0,1,-1} image {1,0,-1} image "atop" object {0,0,-1} image "in" object
• The "over" operators given by and effectively perform alpha blending.
• The "in" operators given by and mask one image with the alpha channel of the other image.
• The "out" operators and mask one image with the complement of the alpha channel of the other image.
• The "atop" operators given by and effectively combine the alpha channels of the two images before performing alpha blending.
Overlay images that are partially transparent:
Specify an explicit position for the overlay:
Specify an alpha-blending parameter:
Overlay two partially transparent images:
Overlay images that are partially transparent:
 Out[1]=

Specify an explicit position for the overlay:
 Out[1]=

Specify an alpha-blending parameter:
 Out[1]=

Overlay two partially transparent images:
 Out[1]=
 Applications   (1)
Create a motion blur effect:
Explore the full range of alpha-compositing modes and parameters:
New in 7