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function Color3DLUTTest
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% A simple test/demo of use of 3D CLUT color correction.
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% Shows some simple test color transformations, performs some CLUT
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% conversion accuracy test at the end, measuring how smaller CLUT sizes /
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% resolutions affect the precision of color conversion.
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% Press any key to progress through different tests/demos.
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% 21.09.2012 mk Written.
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% Open window with 3D CLUT color correction enabled:
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PsychImaging('PrepareConfiguration');
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PsychImaging('AddTask', 'AllViews', 'DisplayColorCorrection', 'LookupTable3D');
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w=PsychImaging('OpenWindow', 0, 0, [0 0 400 400], [], [], [], [], [], kPsychGUIWindow);
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% Build initial identity 3D-CLUT with 16 slots in each color dimension:
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clut = ones(3,16,16,16);
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% Put red-intensity gradient along red-axis of clut cube:
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for i=0:15; clut(1,i+1,:,:) = ones(16,16) * (i/15); end
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% Put green-intensity gradient along gree-axis of clut cube:
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for i=0:15; clut(2,:,i+1,:) = ones(16,16) * (i/15); end
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% Put blue-intensity gradient along blue-axis of clut cube:
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for i=0:15; clut(3,:,:,i+1) = ones(16,16) * (i/15); end
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% Store original identity lut as baseline:
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DrawStim(w, clut, 'Identity mapping: gray gradient, increasing left to right.');
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% Reduce level of verbosity of PsychColorCorrection() to warnings:
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oldverbosity = PsychColorCorrection('Verbosity', 2);
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% Invert red intensity gradient:
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for i=0:15; clut(1,i+1,:,:) = ones(16,16) * (1 - (i/15)); end
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DrawStim(w, clut, 'Identity mapping: Red channel gradient, decreasing left to right.');
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% Invert green intensity gradient:
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for i=0:15; clut(2,:,i+1,:) = ones(16,16) * (1 - (i/15)); end
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DrawStim(w, clut, 'Identity mapping: Green channel gradient, decreasing left to right.');
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% Invert blue intensity gradient:
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for i=0:15; clut(3,:,:,i+1) = ones(16,16) * (1 - (i/15)); end
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DrawStim(w, clut, 'Identity mapping: Blue channel gradient, decreasing left to right.');
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% Only yellow gradient: Clear blue output subvolume:
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DrawStim(w, clut, 'Identity mapping: Yellow gradient, blue channel all-zeros.');
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% Some basic correctness test:
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Screen('FillRect', w, 0);
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% Iterate over various CLUT subsampling levels from full resolution
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% identity mapping to a unit value cube and measure how precision of color
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% mapping degrades with decreasing resolution of the 3D CLUT:
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clut = ones(3,mi+1,mi+1,mi+1);
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% Put red-intensity gradient along red-axis of clut cube:
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for i=0:mi; clut(1,i+1,:,:) = ones(mi+1,mi+1) * (i/mi); end
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% Put green-intensity gradient along gree-axis of clut cube:
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for i=0:mi; clut(2,:,i+1,:) = ones(mi+1,mi+1) * (i/mi); end
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% Put blue-intensity gradient along blue-axis of clut cube:
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for i=0:mi; clut(3,:,:,i+1) = ones(mi+1,mi+1) * (i/mi); end
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PsychColorCorrection('SetLookupTable3D', w, clut);
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% Each RGB input triplet should map to identical output triplet (minus
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% interpolation errors, of course:
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refImage = uint8(rand(400, 400, 3) * 255);
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tex = Screen('MakeTexture', w, refImage);
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Screen('DrawTexture', w, tex);
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% Run pipeline, readback result:
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Screen('DrawingFinished', w);
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testImage = Screen('GetImage', w, [], 'backBuffer');
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% Compute differences:
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diffImage = testImage - refImage;
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maxdiff = max(max(max(diffImage)));
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mindiff = min(min(min(diffImage)));
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meandiff = mean(mean(mean(diffImage)));
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fprintf('k=%i : CLUT Resolution %i : max = %f min = %f mean = %f error.\n', k, mi+1, maxdiff, mindiff, meandiff);
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PsychColorCorrection('Verbosity', oldverbosity);
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function DrawStim(w, clut, label)
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% Draw some test stim:
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Screen('FillOval', w, [255 0 0]);
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% A little intensity gradient from rgb (0,0,0) to (255,255,255):
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Screen('DrawLines', w, [[0 ; 200] , [400 ; 200]], 10, [[0 ; 0 ; 0] , [255 ; 255 ; 255]]);
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% Show label for this test:
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Screen('TextSize', w, 14);
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DrawFormattedText(w, label, 'center', 50, 255);
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PsychColorCorrection('SetLookupTable3D', w, clut);
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% And show the color corrected stim:
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% Wait until keypress:
added
removed
Psychtoolbox/PsychTests/Color3DLUTTest.m
