Specifications

Intel
®
Image Processing Library Reference Manual
5-20
5
If srcImageB does not contain an alpha channel, then
the value (1-
[α
A
)isusedforthealpha,whereα
A
is a
scaled alpha value of
srcImageA in the range 0 to 1.
alphaImageDst The image to use as the alpha channel for dstImage .If
the image already contains an alpha channel, that
channel is used. Otherwise channel 1 in the image is
used as the alpha channel. If this is not suitable for the
application, then the alpha channel number in the image
header for the image should be set appropriately before
calling this function. This argument can be
NULL,in
which case the resultant alpha values are not saved.
premulAlpha A Boolean flag indicating whether or not the input
images contain pre-multiplied alpha values. If true, they
contain these values.
divideMode A Boolean flag related to premulAlpha .Whentrue,the
resultant pixel color (see Table 5-2) is further divided by
the resultant alpha value to get the final resultant pixel
color.
Discussion
The function iplAlphaComposite() performs an image compositing
operation by overlaying the foreground image
srcImageA with the
background image
srcImageB to produce the resultant image dstImage .
The function
iplAlphaComposite() executes under one of the following
conditions for the alpha channels: