I try to zoom out a picture in a picturebox using stretchblt API or paintpicture method , it 's normal working when the picture's width/height under about 6000 pixels, but if over that size, the picturebox will be filled in backcolour, any image date lost.

for example: i try to zoom out a picture (size =800x600) to 800%,
that error is occured and speed of zoom is very slow.
A famous software named ACDSEE is so good do that job, and speed of zoom is big faster than my program.

does anybody know how to solve that problem? pls give me a hand.