- (void)createGLTexture:(GLuint *)texName fromCGImage:(CGImageRef)img

{

GLubyte *spriteData = NULL;

CGContextRef spriteContext;

GLuint imgW, imgH, texW, texH;

imgW = CGImageGetWidth(img);

imgH = CGImageGetHeight(img);

// Find smallest possible powers of 2 for our texture dimensions

for (texW = 1; texW < imgW; texW *= 2) ;

for (texH = 1; texH < imgH; texH *= 2) ;

// Allocated memory needed for the bitmap context

spriteData = (GLubyte *) calloc(texH, texW * 4);

// Uses the bitmatp creation function provided by the Core Graphics framework. 

spriteContext = CGBitmapContextCreate(spriteData, texW, texH, 8, texW * 4, CGImageGetColorSpace(img), kCGImageAlphaPremultipliedLast);

// Translate and scale the context to draw the image upside-down (conflict in flipped-ness between GL textures and CG contexts)

CGContextTranslateCTM(spriteContext, 0., texH);

CGContextScaleCTM(spriteContext, 1., -1.);

// After you create the context, you can draw the sprite image to the context.

CGContextDrawImage(spriteContext, CGRectMake(0.0, 0.0, imgW, imgH), img);

// You don't need the context at this point, so you need to release it to avoid memory leaks.

CGContextRelease(spriteContext);

// Use OpenGL ES to generate a name for the texture.

glGenTextures(1, texName);

// Bind the texture name. 

glBindTexture(GL_TEXTURE_2D, *texName);

// Speidfy a 2D texture image, provideing the a pointer to the image data in memory

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texW, texH, 0, GL_RGBA, GL_UNSIGNED_BYTE, spriteData);

// Set the texture parameters to use a minifying filter and a linear filer (weighted average)

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

// Enable use of the texture

glEnable(GL_TEXTURE_2D);

// Set a blending function to use

glBlendFunc(GL_SRC_ALPHA,GL_ONE);

// Enable blending

glEnable(GL_BLEND);

free(spriteData);

}