/usr/share/psychtoolbox-3/PsychAlphaBlending/AlphaDestinationTerm.m is in psychtoolbox-3-common 3.0.11.20131230.dfsg1-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 | function newDestinationMat=AlphaDestinationTerm(destinationFactorStr, sourceMat, destinationMat)
% newDestinationMat=AlphaDestinationTerm(destinationFactorStr, sourceMatrix, destinationMatrix)
%
% AlphaDestinationTerm simuluates the step of multplying an alpha factor with the
% destination image in OpenGL alpha blending.
%
% Apply an OpenGL source factor rule such as 'GL_ZERO' to the image matrix
% 'destinationMat', returing the dot product of destinationMat and the
% alpha factor selected by string 'sourceFactor'.
%
% The source image matrix 'sourceMat' is required because destination
% factor strings may select alpha values from the source image.
%
% AlphaDestinationTerm calculates with double-precision (64-bit) floating
% point arithmatitic whereas the precision of an OpenGL renderer which it
% simulates is unspecified, except that OpenGL guarantees perfect precision
% for alpha values 0 and 1 (255 via Screen). Comparison of
% AlphaDestinationTerm with the OpenGL renderer shows that alpha
% multiplicaion discards up to one bit of precision.
%
% see also: AlphaSourceTerm, PsychAlphaBlending
% HISTORY
%
% mm/dd/yy
%
% 2/11/05 awi wrote it.
sourceMatDims=size(sourceMat);
destinationMatDims=size(destinationMat);
if length(sourceMatDims) ~= 3 || sourceMatDims(3) ~= 4
error('Argument ''sourceMat'' must be a matrix with dimensions [x,y,4]');
end
if length(destinationMatDims) ~= 3 || destinationMatDims(3) ~= 4
error('Argument ''destinationMat'' must be a matrix with dimensions [x,y,4]');
end
sourceMatAlphaPlane=sourceMat(:,:,4);
destinationMatAlphaPlane=destinationMat(:,:,4);
if strcmp(destinationFactorStr, 'GL_ZERO')
newDestinationMat=AlphaTimes(destinationMat,0);
elseif strcmp(destinationFactorStr, 'GL_ONE')
newDestinationMat=AlphaTimes(destinationMat,255);
elseif strcmp(destinationFactorStr, 'GL_SRC_COLOR')
newDestinationMat=AlphaTimes(destinationMat, sourceMat);
elseif strcmp(destinationFactorStr, 'GL_ONE_MINUS_SRC_COLOR')
newDestinationMat=AlphaTimes(destinationMat, 255 - sourceMat);
elseif strcmp(destinationFactorStr, 'GL_SRC_ALPHA');
newDestinationMat=AlphaTimes(destinationMat, sourceMat(:,:,4));
elseif strcmp(destinationFactorStr, 'GL_ONE_MINUS_SRC_ALPHA')
newDestinationMat=AlphaTimes(destinationMat, 255 - sourceMat(:,:,4));
elseif strcmp(destinationFactorStr, 'GL_DST_ALPHA');
newDestinationMat=AlphaTimes(destinationMat, destinationMat(:,:,4));
elseif strcmp(destinationFactorStr, 'GL_ONE_MINUS_DST_ALPHA');
newDestinationMat=AlphaTimes(destinationMat, 255-destinationMat(:,:,4));
else
error('Argument "sourceFactor" is unrecognized or invalid');
end
|