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function retpixels = glReadPixels( x, y, width, height, format, type, bufferoffset )
% glReadPixels Interface to OpenGL function glReadPixels
%
% usage:
% For standard readback into a Matlab or Octave image matrix:
% retpixels = glReadPixels( x, y, width, height, format, type )
%
% For readback into the currently bound OpenGL Pixelbuffer object (PBO):
% glReadPixels( x, y, width, height, format, type, bufferoffset )
% where bufferoffset is the positive integer byte-offset into the PBO.
%
% C function: void glReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid* retpixels)
% 24-Jan-2006 -- created (generated automatically from header files)
% 25-Jan-2006 -- return argument allocated for case format=GL_RGB,
% type=GL_UNSIGNED_BYTE (RFM)
% 13-Jun-2009 -- Remove special code for Octave -> No longer needed. (MK)
% ---allocate---
% ---protected---
if nargout > 0
% Standard path: Readback pixels to host memory, return image in return
% argument 'retpixels':
if nargin~=6,
error('Invalid number of arguments: Must be (x, y, width, height, format, type) for readback to host-memory.');
end
bufferoffset = -1;
else
% PBO backed path: Readback into a Pixelbuffer object. Nothing is
% directly returned to Matlab, but instead the read pixels are written
% to the currently bound pixelbuffer object at the offset provided by
% 'bufferoffset'
if nargin~=7,
error('Invalid number of arguments: Must be (x, y, width, height, format, type, bufferoffset) for readback into PBO.');
end
if isempty(bufferoffset)
error('You must provide a valid "bufferoffset" into the PBO!');
end
if bufferoffset < 0
error('You must provide a valid, zero or positive integral "bufferoffset" into the PBO!');
end
end
% check format and type
global GL
if x < 0 || y<0
error('Invalid (negative) (x,y) offset passed to glReadPixels.');
end;
if width <= 0 || height<=0
error('Invalid (negative or zero) (width, height) passed to glReadPixels.');
end;
switch(format)
case {GL.RED, GL.GREEN, GL.BLUE, GL.ALPHA, GL.LUMINANCE, GL.INTENSITY, GL.DEPTH_COMPONENT, GL.STENCIL_INDEX }
numperpixel = 1;
case {GL.LUMINANCE_ALPHA }
numperpixel = 2;
case {GL.RGB , GL.BGR }
numperpixel = 3;
case {GL.RGBA , GL.BGRA }
numperpixel = 4;
otherwise
error('Invalid format passed to glReadPixels.');
end;
if bufferoffset == -1
% Readback to host memory, aka Matlab- or Octave- matrix:
% Allocate memory:
pixels=zeros(numperpixel, width, height, 2);
% Tell OpenGL that we accept byte-aligned aka unaligned data.
glPixelStorei(GL.PACK_ALIGNMENT, 1);
% Perform proper type-cast:
switch(type)
case GL.UNSIGNED_BYTE
pixels = uint8(pixels);
pclass = 'uint8';
case GL.BYTE
pixels = int8(pixels);
pclass = 'int8';
case GL.UNSIGNED_SHORT
pixels = uint16(pixels);
pclass = 'uint16';
case GL.SHORT
pixels = int16(pixels);
pclass = 'int16';
case GL.UNSIGNED_INT
pixels = uint32(pixels);
pclass = 'uint32';
case GL.INT
pixels = int32(pixels);
pclass = 'int32';
case GL.FLOAT
pixels = moglsingle(pixels);
pclass = 'double';
otherwise
error('Invalid type argument passed to glReadPixels()!');
end;
% Execute actual call:
moglcore( 'glReadPixels', x, y, width, height, format, type, pixels );
% Hack around Matlab R2015b+ bug: Needs > 1 component to be passed into
% moglcore as prhs argument for data return to work, so we extend pixels
% by a 4th dimension with one useless 2nd layer, which we strip away here
% again before returning data to usercode. The 2nd layer guarantees that
% prhs pixels has at least 2 components if width=height=numperpixel==1
pixels = pixels(:,:,:,1);
% Rearrange data in Matlab friendly format:
retpixels = zeros(size(pixels,2), size(pixels,3), size(pixels,1), pclass);
for i=1:numperpixel
retpixels(:,:,i) = pixels(i,:,:);
end;
else
% Readback into bound Pixelbuffer object PBO:
moglcore( 'glReadPixels', x, y, width, height, format, type, bufferoffset );
retpixels = [];
end
return
% ---autocode---
%
% function pixels = glReadPixels( x, y, width, height, format, type )
%
% % glReadPixels Interface to OpenGL function glReadPixels
% %
% % usage: pixels = glReadPixels( x, y, width, height, format, type )
% %
% % C function: void glReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid* pixels)
%
% % 05-Mar-2006 -- created (generated automatically from header files)
%
% % ---allocate---
%
% if nargin~=6,
% error('invalid number of arguments');
% end
%
% pixels = (0);
%
% moglcore( 'glReadPixels', x, y, width, height, format, type, pixels );
%
% return
%
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