Ross Boylan wrote:
On Tue, 2010-04-13 at 21:05 -0700, Andreas Raab wrote:
Hi Ross -
Profiling is your friend. In most cases, 95% of the time are spent in 5% of the code. From what you're saying below it sounds that you're using one of the 'special' PNG modes (black and white, or gray-scale) that probably have seen less attention for optimization than others. Any chance you can post a sample image for profiling it?
I've attached a test image, which takes about 30 seconds for me. It is a 1 bit depth image. Not sure if the attachment will make it through....
Ross
Profiling is indeed your friend. There is some serious inefficiency there. Quickly hacking this (warning: will only work for 1bpp):
copyPixelsGray: y "Handle non-interlaced grayscale color mode (colorType = 0)" | word base ii | base := y * form width//32 +1. 0 to: thisScanline size-1 // 4 do: [ :i | ii := i * 4. word := (thisScanline at: ii+1) << 24 bitOr: ( (thisScanline at: ii+2) << 16 bitOr: ( (thisScanline at: ii+3) << 8 bitOr: ( (thisScanline at: ii+4)))). form bits at: base + i put: word ].
gives over 30x speed increase (from 10 seconds down to 310 mSec) on my system. This is not a solution, just some food for thought.
Cheers, Juan Vuletich