Well, you're not stretching the pixels, you're actually asking your image editing software to fill in the missing pixels by interpolating from the actual pixels around it. So, if you enlarge your image from 640x480 to 1280x960, this is effectively 4 times as many pixels as your original image, which the software has to insert. Since it is really only making an educated guess about what colours those pixels should be, the net effect is loss of detail, blurriness, and blockiness after compression. The bigger the enlargement factor, the more inaccurate the process becomes, and you'll eventually e