/usr/share/psychtoolbox-3/PsychGLImageProcessing/MakeTextureDrawShader.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 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 90 91 92 93 94 | function glsl = MakeTextureDrawShader(windowPtr, shadertype, backgroundColorOffset)
% glsl = MakeTextureDrawShader(windowPtr, shadertype [, backgroundColorOffset = [0,0,0,0]]);
%
% Create a special GLSL shader that can apply some special image processing
% operations that modify the normal drawing of textures via
% Screen('DrawTexture(s)'). Return a handle 'glsl' to the shader.
%
% The created shader can be attached to specific textures via passing the
% returned 'glsl' argument as the optional 'textureShader' argument for the
% Screen('MakeTexture', ....., textureShader); function. It can be also
% applied on a per-draw basis by passing the 'glsl' handle as optional
% 'textureShader' argument to the Screen('DrawTexture(s)', ...); function.
%
%
% Mandatory arguments:
%
% 'windowPtr' A handle to the onscreen window to which the shader should be
% associated.
%
% 'shadertype' A name string that defines the type of shader / image
% processing operation to apply. It can be one of the following:
%
% - 'SeparateAlphaChannel': Alpha values are looked up at the regular
% locations defined via the 'srcRect' parameter in a Screen('DrawTexture')
% call. RGB color values are looked up at srcRect, offset by some (dx,dy)
% offset, as provided by the 'auxParameters' vector [dx, dy, 0, 0].
% Providing non-zero offset values for dx and dy allows to "shift" or
% "scroll" the RGB or Luminance image inside a texture during drawing,
% while keeping the alpha image at a fixed location, solely defined by
% 'srcRect'. This is mostly useful if you want to draw some drifting
% stimulus with a fixed alpha channel mask applied, ie., the color image
% should move, but the alpha mask should stay fixed.
%
% - 'PremultipliedAlphaChannel': Like 'SeparateAlphaChannel', but the alpha
% value is not written to the framebuffer, but premultiplied to the RGB
% color pixel before writeout.
%
% 'backgroundColorOffset' Optional, defaults to [0 0 0 0]. A RGBA offset
% color to add to the final RGBA colors of the drawn texture, prior to
% drawing it.
%
% History:
% 03/31/2009 Written. (MK)
% Global GL struct: Will be initialized in the LoadGLSLProgramFromFiles below:
global GL; %#ok<NUSED>
% Make sure we have support for shaders, abort otherwise:
AssertGLSL;
if nargin < 2
error('You must provide the "windowPtr" and "shadertype" arguments!');
end
if nargin < 3
backgroundColorOffset = [];
end
if isempty(backgroundColorOffset)
backgroundColorOffset = [0 0 0 0];
else
if length(backgroundColorOffset) < 4
error('The "backgroundColorOffset" must be a 4 component RGBA vector [red green blue alpha]!');
end
end
% This dummy-call just makes sure the context of the proper window 'windowPtr' is bound:
Screen('GetWindowInfo', windowPtr);
switch shadertype
case {'SeparateAlphaChannel'}
% Load shader for separate lookup of RGB and alpha channels:
glsl = LoadGLSLProgramFromFiles('SeparateAlphaTextureShader', 1);
case {'PremultipliedAlphaChannel'}
% Load shader for separate lookup of RGB and alpha channels with premultiplied alpha:
glsl = LoadGLSLProgramFromFiles('PremultipliedAlphaTextureShader', 1);
otherwise
error('Unknown or unsupported "shadertype" string provided!');
end
% Setup shader:
glUseProgram(glsl);
% Set backgroundColorOffset:
glUniform4f(glGetUniformLocation(glsl, 'Offset'), backgroundColorOffset(1),backgroundColorOffset(2),backgroundColorOffset(3),backgroundColorOffset(4));
% Setup done.
glUseProgram(0);
% Ready!
return;
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