Image mask usage. Specifies how the mask or alpha channel of the image is used for operations on the image (for example, colorize=). When specified in an effect layer, it allows applying the effect to the background area of parent layer or to the entire parent layer rectangle.
maskUse=norm|invert|off
The following table illustrates the effect of maskUse=
depending on availability and type of the mask (alpha channel) associated with the layer image.
Value | No mask | Unassociated alpha (or separate mask image) | Associated (pre-multiplied) alpha |
---|---|---|---|
off |
Opaque image rectangle |
Opaque image rectangle |
Foreground area of image over rectangle filled with solid black |
norm |
Opaque image rectangle |
Foreground area of image |
Foreground area of image or layer |
invert |
Hidden layer |
Background area of image |
Background area of image or layer filled with solid black |
Image or layer attribute. Applies to layer 0 if layer=comp
. If specified in an effect layer, the command modifies the mask inherited from the parent layer.
The behavior of maskUse=
is undefined and unsupported when specified with text or solid color layers when no image mask is applicable (specified with mask=
or catalog::Mask
).
maskUse=norm
Colorize the background area of an image; the image foreground is defined by a separate mask image. This is achieved by layering the colorized image background on top if the unmodified image:
http://server/myRootId/myImageId?layer=1&src=myImageId&mask=myImgMask&maskUse=invert&colorize=0x306090