>Psychtoolbox>PsychRects

r = ScaleRect(r,horizontalFactor,verticalFactor)

Scales a rect, by multiplying the left and right coordinates by the
horizontal scale factor and multiplying the top and bottom coordinates
by the vertical scale factor. Also see Expand and InsetRect.
Input can be multiple rects, concatenated into a Mx4 matrix

Also see PsychRects.