[racket] about image operation

I still wonder how kind of google earth rotate image very fast
anyway, thank you for your advice~!


2010/10/10 Stephen Bloch <sbloch at adelphi.edu>

> 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
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