Stamps come in a range of sizes and can be enlarged automatically. In The Gimp, the mask is shown alongside the layer.
This is only feasible with Photoshop 4 or later however, channels may be seen in Photoshop Elements. Locate the stamps in Tux Paint and open them in a photo editing program like Photoshop or The GIMP to examine the four channels, notably the Alpha channel, which is the mask.
Each stamp includes a mask that crops the picture, enabling any type of stamp to be used. Stamps are images that have a mask over them.
