ImageCompose

ImageCompose[image, overlay] gives the result of overlaying overlay onto image.

ImageCompose[image, {overlay, α}] uses alpha blending with fraction α.

Examples

Overlay an image:

img = ExampleData[{"TestImage", "Lena"}];
overlay = Image[Graphics[{Red, Disk[]}], ImageSize -> 100];
ImageCompose[img, overlay]

With transparency:

ImageCompose[img, {overlay, 0.5}]

Please visit the official Wolfram Language Reference for more details.