/usr/share/psychtoolbox-3/PsychAlphaBlending/SetDestinationAlpha.m is in psychtoolbox-3-common 3.0.11.20140816.dfsg1-1.
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 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 | function [newSourceImage, newDestinationImage]=SetDestinationAlpha(destinationFactorStr, alpha, sourceImage, destinationImage)
% [newSourceMat, newDestinationMat]=SetDestinationAlpha(destinationFactorStr, alpha, sourceImage, destinationImage)
%
% Given an alpha blending factor, "destinationFactorStr", insert "alpha"
% into the source or destination image such that on alpha blending with the
% specified destinationFactorStr "alpha" is selected as the destination
% alpha.
%
% For some combinations of destination factor string and source factor
% string, SetDestinationAlpha may undo a subsequent call to SetSourceAlpha
% or be undone by a previous call to SetSourceAlpha. This happens when
% both the destination factor string and the source factor string specify
% the same location of alpha values yet store different alpha values. For
% example, if both the source alpha and destination alpha are drawn from
% the source alpha plane (GL_SRC_ALPHA) then setting the source alpha to 0
% would also change the destination alpha to 0. Both source and destination
% would share the source alpha plane for storage of the alpha value.
%
% SetAlphaDestination helps test OpenGL alpha blending precision.
%
% see also: PsychAlphaBlending
% HISTORY
%
% mm/dd/yy
%
% 2/17/05 awi wrote it.
%expand alpha to be an alpha plane
destinationMatDims=size(destinationImage);
alphaMatDims=size(alpha) ;
if alphaMatDims(1)*alphaMatDims(2)==1
alphaPlane=repmat(alpha, destinationMatDims(1), destinationMatDims(2));
else
alphaPlane=alpha;
end
glOnePlane=repmat(255, destinationMatDims(1), destinationMatDims(2));
glZeroPlane=zeros(destinationMatDims(1), destinationMatDims(2));
%insert the alpha into the storage location for alpha
if strcmp(destinationFactorStr, 'GL_ZERO')
if any(any(alpha ~= 0))
error('destination factor GL_ZERO is incompatible with alpha values not equal to 0.');
end
%change nothing
newSourceImage=sourceImage;
newDestinationImage=destinationImage;
elseif strcmp(destinationFactorStr, 'GL_ONE')
if any(any(alpha ~= 255))
error('destination factor GL_ONE is incompatible with alpha values not equal to 255.');
end
%change nothing
newSourceImage=sourceImage;
newDestinationImage=destinationImage;
elseif strcmp(destinationFactorStr, 'GL_SRC_COLOR')
%change source image
newSourceImage=repmat(alphaPlane,[1,1,4]);
newDestinationImage=destinationImage;
elseif strcmp(destinationFactorStr, 'GL_ONE_MINUS_SRC_COLOR')
%change source image
newSourceImage=255-repmat(alphaPlane,[1,1,4]);
newDestinationImage=destinationImage;
elseif strcmp(destinationFactorStr, 'GL_SRC_ALPHA');
%change source image
newSourceImage=sourceImage;
newSourceImage(:,:,4)=alphaPlane;
newDestinationImage=destinationImage;
elseif strcmp(destinationFactorStr, 'GL_ONE_MINUS_SRC_ALPHA')
%change source image
newSourceImage=sourceImage;
newSourceImage(:,:,4)=255-alphaPlane;
newDestinationImage=destinationImage;
elseif strcmp(destinationFactorStr, 'GL_DST_ALPHA');
%change the destination image
newSourceImage=sourceImage;
newDestinationImage=destinationImage;
newDestinationImage(:,:,4)=alphaPlane;
elseif strcmp(destinationFactorStr, 'GL_ONE_MINUS_DST_ALPHA');
%change the destination image
newSourceImage=sourceImage;
newDestinationImage=destinationImage;
newDestinationImage(:,:,4)=255-alphaPlane;
else
error('Argument "sourceFactor" is unrecognized or invalid');
end
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