Compositing

IceMan Reference Guide

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"

Over(fg)

fg: Foreground image (Image)

The image being operated on is the background image.


		fg := IceImage With("teapot.tif")
		bg := IceImage With("tinbox.tif")
		result := bg Over(fg)

Cover(fg)

fg: Foreground image

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


		fg := IceImage With("teapot.tif")
		bg := IceImage With("tinbox.tif")
		result := bg Cover(fg)

Atop(fg)

fg: Foreground image (Image)

Merge "atop".


		fg := IceImage With("teapot.tif")
		bg := IceImage With("tinbox.tif")
		result := bg Atop(fg)

In(fg)

fg: Foreground image (Image)

Merge "in".


		fg := IceImage with('teapot.tif')
		bg := IceImage with('tinbox.tif')
		result := bg In(fg)

MergeXor(fg)

fg: Foreground image (Image)

Merge XOR operation.


		fg := IceImage With("teapot.tif")
		bg := IceImage With("tinbox.tif")
		result := bg MergeXor(fg)

Out(fg)

fg: Foreground image (Image)

Merge out operation.


		fg := IceImage With("teapot.tif")
		bg := IceImage With("tinbox.tif")
		result := bg Out(fg)

TransmissionFilter(fg)

fg: Foreground image (Image)

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


		fg := IceImage With("teapot.tif")
		bg := IceImage With("tinbox.tif")
		result := bg TransmissionFilter(fg)

AlphaDivide()

Divide image by alpha channel.

AlphaMultiply()

Multiply image by alpha channel.

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