Trying to squeeze a bit more speed out of certain bottlenecks in my
code. Here's one of them:
NSBitmapImageRep* bits = [self pathBitmapInRect:ir];
// if any pixels in this bitmap are set, we have a hit.
int x, y;
unsigned pixel;
for( y = 0; y < ir.size.height; ++y )
{
for( x = 0; x < ir.size.width; ++x )
{
[bits getPixel:&pixel atX:x y:y];
if ( pixel < 255 )
{
hit = YES;
goto endOfLoop;
}
}
}
endOfLoop:
The <bits> object is a grayscale bitmap where the background is
painted white and any set pixels are painted black. I just need to
know if there are *any* black pixels in the image. <ir> is an NSRect
which can be any size. The imaging method (not shown) accounts for the
origin of this rect, so the test scans from 0,0. The purpose is to
test whether a given rect intersects a rendered object (path), not
just test a point against it.
Is there any faster way of doing this than just iterating over the
pixels like this? I can't think of anything but someone might have a
bright idea.
tia,
Graham
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