Extremely slow imshow() when using 16-bit images
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I'm starting by taking a matrix of data from a DICOM file and making it indexed (so that I can apply a user-specified colormap).
shades = 2^bit_val
grayData = mat2gray(dicomData);
% Limiting to shades-1 to allow for a special mark-up color
indexedData = gray2ind(data, shades-1);
%Then code to calculate cmap with the special color at the end
...
imshow(indexedData, cmap, handles.Axes);
If bit_val is 8, then the code takes 0.01 seconds to display which is fine. However, if bit_val is 16, then it takes nearly a whole second to display.
The primary issue is that I want to be able to quickly/smoothly switch between different slices being displayed.
Is there any way to improve the rendering time?
Edit:
According to Wikipedia's entry for palette ( http://en.wikipedia.org/wiki/Palette_%28computing%29#System_and_logical_palettes_under_Microsoft_Windows )
Under Windows, "When a given application intends to output colorized graphics and/or images, it can set their own logical palette, that is, its own private selection of colors (up to 256)."
Perhaps this explains why an 8-bit color map (with only 256 colors) displays faster than a 16-bit color map (with 65536 colors) on Windows.
3 Comments
Answers (1)
Sean de Wolski
on 12 Dec 2012
Edited: Sean de Wolski
on 12 Dec 2012
X = uint16(rand(1000)*60000);
t = 0;
figure;ax = axes;
for ii = 1:10
tic;
imshow(X,'parent',ax);
drawnow;
t = t+toc;
cla;
drawnow;
end
disp(t/10);
% 0.0335 on my system
Also Have you seen implay()?
doc implay
4 Comments
Sean de Wolski
on 17 Dec 2012
@Christopher: Put this in a loop (like I did) and run it in a script file. That way you don't get any overhead that may be introduced by the command window.
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