On Mon, 30 May 2011, Tomas Hajny wrote:
On Mon, May 30, 2011 16:16, michael.vancann...@wisa.be wrote:
Try the following code:
Img:=TFPMemoryImage.Create(0,0);
Img.UsePalette:=False;
Img.loadFromFile(FileList[i]);
That should work much faster. The reason is probably that the default
image
created by the reader uses a palette, which is of course dog slow when
reading
large images.
Interesting. What is supposed to be a "large image"? I ask because the
original post mentioned 35 kB and 65 kB (and indirectly also dimensions
around 600x400 if I understand the program output correctly) which I
certainly wouldn't consider as "large" (and the mentioned time necessary
for reading it surely not appropriate regardless of using palette or not).
I guess that some optimization may be reasonable because such pictures
could be loaded and displayed (including conversion from true colour to
256 colours palette) faster even on a 486 machine...
It depends on the colors used. The default palette algorithm simply
allocates a slot per found color in the jpg and returns the index of the
slow. For a picture, this will create a huge palette, in which the search
for a color is in essence linear, so n^2 lookups.
So, dog slow.
You could obviously speed this up by creating a palette yourself, and
limiting the number of colors.
Or, best for pictures is not to use a palette, which is what my solution
entails.
Michael.
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