How to efficiently update an image if one matrix element is changed
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I have a matrix in which I change only one element in every iteration of a loop. I want to display that matrix as an image using image or imagesc. What I am doing now is to update the CData property of the image handle so as to refresh the image of the matrix. With several thousands of iterations, it turned out that the bottleneck is the image/imagesc function according to the Profiler. So I thought of changing the color of the tile corresponding to the changed matrix entry. How can I do that? There would be no problem with the colormap since the matrix only contains zeros and ones.
Image Analyst on 18 Oct 2015
Don't use image. Use set(). See this demo:
grayImage = imread('moon.tif');
hImage = imshow(grayImage);
promptMessage = sprintf('Do you want to assign new pixels,\nor Quit?');
titleBarCaption = 'Continue?';
buttonText = questdlg(promptMessage, titleBarCaption, 'Continue', 'Quit', 'Continue');
if strcmpi(buttonText, 'Quit')
for k = 1 : 50 : numel(grayImage);
grayImage(k) = 255; % Make this pixel bright white.
set(hImage, 'CData', grayImage);
I think it should be fast enough for you.