When we need to look at two images together—for example, to compare the input and output of a particular image processing operation, or to compare different images of the same scene—overlaying one image on top of the other is often more effective than viewing the images side-by-side. Each pixel in a Handle Graphics® image object can be assigned a different level of transparency using the ‘AlphaData’ property of the image. The ‘AlphaData’ is a MxN matrix of the same size as the image with each element in the range [0 1] indicating the “opacity” of a pixel.
This article focuses on two transparency patterns that can be applied to create a wide variety of image visualizations: a checkerboard that shows portions of two images in an alternating pattern of squares, and a data-dependent pattern that uses varying shades of a single color
By Steve Eddins, The MathWorks
This article was published in The MathWorks News & Notes, 2009