ImageCompose

ImageCompose[image, overlay]
gives the result of overlaying overlay onto image.

ImageCompose[image, {overlay, }]
gives the result of alpha blending overlay into image using blending fraction .

ImageCompose[image, overlay, pos]
places the center of overlay at position pos in image.

ImageCompose[image, overlay, pos, opos]
places the point opos in overlay at position pos in image.

ImageCompose[image, overlay, pos, opos, {fi, fo, mode}]
uses the compositing fractions and the specified compositing mode.

DetailsDetails

  • ImageCompose[image, ...] always gives an image with the same pixel size as image.
  • ImageCompose[image, overlay] does alpha blending if overlay has an alpha channel.
  • ImageCompose[image, {overlay, }] effectively sets the alpha value for overlay to , or multiplies an existing alpha channel by .
  • ImageCompose[image, overlay] composes overlay pixel-by-pixel onto image, without changing the size of overlay.
  • The overlay can be either an explicit image object, or a graphics object that is automatically rasterized to have the same image size as image.
  • ImageCompose[image, overlay] centers overlay in image.
  • The position pos in image or the position opos in overlay 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
  • Possible named positions include Top, Bottom, Left, Right, Center.
  • 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 overlay.
  • ImageCompose[image, ...] yields an image with an alpha channel only if image has an alpha channel.
  • ImageCompose[{image, i}, ...] effectively adds an alpha channel with value to image.
  • ImageCompose[..., {fi, fo, mode}] combines a fraction of every pixel value in image with a fraction of every pixel value in overlay, in all cases taking account of alpha channels.
  • With value for mode, overlay is treated as on top of image. With value it is treated as underneath. And with value , image and overlay 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.
  • ImageCompose[image, {o1, o2, ...}] composes multiple images onto image.
  • Using ImageCompose[image, {{o1, 1}, ...}], different alpha values can be set for different overlays.
  • Corresponding lists of positions, overlay positions, and compositing fractions and modes can also be specified when composing with multiple overlays.

ExamplesExamplesopen allclose all

Basic Examples (5)Basic Examples (5)

Overlay images that are partially transparent:

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Specify a scaled position for the center of the overlay:

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Specify an explicit position for the overlay:

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Specify an alpha-blending parameter:

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Overlay two partially transparent images:

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New in 7 | Last modified in 9
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