Free appplication that calculates the area of a picture. The backgroud will be recognised on hand of the alpha channel. The threshold of the alpha channel (opacity) can be modified. It does not matter in which unit you have entered the picture width. The result will be the square of the used unit.
PictureArea supports all native OS X picture formats like PNG, PSD and TIFF. Pictures w/o an alpha channel can not be calculated.
Icon Mask Maker
