Ok,
so I got this now (see below).
However, the line ...
[imageToUse unbindTextureRepresentationFromCGLContext:cgl_ctx
textureUnit:GL_TEXTURE0];
gets me an error in the Output window of XCode:
2012-11-22 14:39:17.928 Quartz Composer[9102:303] *** OpenGL error
0x0502 (invalid operation) in function "-[QCPlugInInputImage
unbindTextureRepresentationFromCGLContext:textureUnit:]"
This said, I don't understand why? I mean, this call is balanced with a
call to "bindTextureRepresentationToCGLContext" in the beginning and the
used textureUnit is GL_TEXTURE0?
----> my code from hereon -------->
CGLContextObj cgl_ctx = [context CGLContextObj];
GLenum error;
if (![imageToUse lockTextureRepresentationWithColorSpace:colorSpace
forBounds:[imageToUse imageBounds]])
{
NSLog(@"Locking of texture failed.");
return NO;
}
//
[imageToUse bindTextureRepresentationToCGLContext:cgl_ctx
textureUnit:GL_TEXTURE0 normalizeCoordinates:YES];
// scaling in opengl comes here...
const GLuint scaledTexture;
const GLuint myFBO;
int width = self.inputWidthLEDWall;
int height = self.inputHeightLEDWall;
glGenTextures(1, &scaledTexture); // make the destination
scaled texture
// TODO: set up texture dimensions via glTexImage2D
glGenFramebuffers(1, &myFBO); // make the drawing FBO to
perform the scaling
glBindFramebuffer(GL_FRAMEBUFFER_EXT, myFBO);
glFramebufferTexture2D(GL_FRAMEBUFFER_EXT,
GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, scaledTexture, 0);
glDrawBuffer(GL_COLOR_ATTACHMENT0);
// bind source texture -- you might just use the bindTextureRep
call here?
//glBindTexture(GL_TEXTURE_2D (or rect?), GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, GL_TEXTURE0);
// set up projection -- pixel-for-pixel orthographic
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0,width,height,0,0,1);
// draw the source to the destination
// TODO: if better-than-bilinear-scaling is desired, add a shader
here to do bicubic or something
glBegin(GL_QUADS);
glTexCoord2f(0,0);
glVertex2f(0,0);
glTexCoord2f(1,0);
glVertex2f(width,0);
glTexCoord2f(1,1);
glVertex2f(width,height);
glTexCoord2f(0,1);
glVertex2d(0, height);
glEnd();
// done! scaledTexture now has the scaled contents using bilinear
scaling in hardware
// make sure to delete fbos and texture when done.
GLvoid* pixelData = malloc(width * height *3);
glReadPixels(0,0,width, height, GL_RGB, GL_UNSIGNED_INT_8_8_8_8,
&pixelData);
free(pixelData);
glDeleteTextures(1, &scaledTexture);
glDeleteBuffers(1, &myFBO);
[imageToUse unbindTextureRepresentationFromCGLContext:cgl_ctx
textureUnit:GL_TEXTURE0];
[imageToUse unlockTextureRepresentation];
--
Christophe Leske
multimedial.de
----------------------------------------
www.multimedial.de - i...@multimedial.de
Hohler Strasse 17 - 51645 Gummersbach
+49(0)2261-99824540 // +49(0)177-2497031
----------------------------------------
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