Compositing

Compositing

The basic image merging operations defined by Porter and Duff in their 1984 paper, with a couple of additions.  All these operations are methods of Image and return a new Image instance.

Each of the following operations is illustrated with these foreground and background images:

teapot.tif

Alpha channel of "teapot.tif"

tinbox.tif

Alpha channel of "tinbox.tif"

ice.Image Over(fg)

fg: Foreground image (ice.Image).

The image being operated on is the background image.

fg = ice.Load('teapot.tif') bg = ice.Load('tinbox.tif') result = bg.Over(fg)

ice.Image Cover(fg)

fg: Foreground image (ice.Image).

Correlated Over operation.  Similar to Over, but works better for correlated subpixel coverage.

fg = ice.Load('teapot.tif') bg = ice.Load('tinbox.tif') result = bg.Cover(fg)

ice.Image MergeAtop(fg)

fg: Foreground image (ice.Image).

Merge "atop".

fg = ice.Load('teapot.tif') bg = ice.Load('tinbox.tif') result = bg.MergeAtop(fg)

ice.Image In(fg)

fg: Foreground image (ice.Image).

Merge "in".

fg = ice.Load('teapot.tif') bg = ice.Load('tinbox.tif') result = bg.In(fg)

ice.Image MergeXOR(fg)

fg: Foreground image (ice.Image).

Merge XOR operation.

fg = ice.Load('teapot.tif') bg = ice.Load('tinbox.tif') result = bg.MergeXOR(fg)

ice.Image Out(fg)

fg: Foreground image (ice.Image).

Merge out operation.

fg = ice.Load('teapot.tif') bg = ice.Load('tinbox.tif') result = bg.Out(fg)

ice.Image TransmissionFilter(fg)

fg: Foreground image (ice.Image).

In this operation, the foreground acts as a color filter for the background.

fg = ice.Load('teapot.tif') bg = ice.Load('tinbox.tif') result = bg.TransmissionFilter(fg)

ice.Image AlphaDivide()

Divide image by alpha channel.

ice.Image AlphaMultiply()

Multiply image by alpha channel.