Overlaying color image on grayscale image

I have two images, one in grayscale and one in color. The color image is a quantitative map (e.g. blood flow), while the grayscale simply shows anatomy. How can I segment out a portion of the color image and overlay on the grayscale image?

Answer 1

[Walter Roberson]

image(TheGrayscaleImage);
colormap(gray(256));
hold on
image(TheColorImage, 'AlphaData', YourTransparencyData)

YourTransparencyData should be 1 in the places you want TheColorImage to completely show up, 0 in the places where you want the grayscale image to be completely visible and the color image not visible, and anything inbetween for the places you want to "blend" the two images.