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Issue 8.2


Blending by Layers

Using layers for powerful graphical effects

Issue: 8.2 (January/February 2010)
Author: JC Cruz
Author Bio: JC is a freelance technical writer living in British Columbia. He writes for various publications, pokes around with Cocoa, Python, and REALbasic, and spends time with his nephew. He can be reached at anarakisware@gmail.com
Article Description: No description available.
Article Length (in bytes): 55,116
Starting Page Number: 35
Article Number: 8211
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Download Icon 8211.zip Updated: 2010-01-04 13:06:07

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Excerpt of article text...

Welcome once again to REALGraphics, your guide to the field of image processing. Today, we will explore the concept of layer blends. We will study four groups of blends and the mathematics of each blend. Next, we will build a blending engine using REALbasic. And we will test the engine against two standard images.

The Concept of Layers

Many high-end image editors come with a Layers feature. This feature combines two or more images using a blend or composite operation. It may process the entire set of image data or just a portion of each image. Overall, the feature is akin to the darkroom process of stacking multiple photo negatives in order to form a composite positive.

The Layers feature first appeared in the commercial product Fauve Matisse, which later became Macromedia xRes. It gained widespread use when it became part of Adobe Photoshop 3.0 in the mid-1990s. The feature is also present in the open-source GIMP editor and its many variants.

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