[racket] about image operation

On Oct 10, 2010, at 4:17 AM, 김태윤 <kty1104 at gmail.com> wrote:

> there is little images(16x16) that cropped from other chipset
> and I gether them and make an image which size is about 320 x 320
> 
> and I rotate it, but it is very very slow and blink alot

This is because it really does take a lot of processing to rotate  a bitmap image by an arbitrary angle.  I bet it's really fast if you rotate by exactly 90 degrees....

> so I test basic polygon
> it works perfectly, no delay, no blinking, even if when it grows big

Yes, that's because a polygon is determined by just a few points, so there's a lot less processing to be done.

If it makes you feel better, in the old image library the polygon would have been just as slow as the bitmap :-)

I don't know enough about the internals of the image library to tell you how to speed up operations on the former picture.

Stephen Bloch