This procedure mirrors the colormap destructively and vertically thus exchanging the upper and lower half accordingly.
The colormap is modified.
The mirrored colormap is returned.
> (define image (colormap-readjpg "horses.jpg")) image > (colormap-writejpg (colormap-vmirror! image) "horses-vmirrored.jpg") ok >
The input image displays as follows (horses.jpg, JPG, 2400x1600):
The vertically mirrored image looks like this: