Extremely slow imshow() when using 16-bit images
3 views (last 30 days)
Show older comments
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.
See Also
Categories
Find more on Display Image in Help Center and File Exchange
Products
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!