How Can I Compress Texture in OpenGL on iPhone/iPad?
- by nonamelive
Hi,
I'm making an iPad app which needs OpenGL to do a flip animation. I have a front image texture and a back image texture. Both the two textures are screenshots.
// Capture an image of the screen
UIGraphicsBeginImageContext(view.bounds.size);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// Allocate some memory for the texture
GLubyte *textureData = (GLubyte*)calloc(maxTextureSize*4, maxTextureSize);
// Create a drawing context to draw image into texture memory
CGContextRef textureContext = CGBitmapContextCreate(textureData, maxTextureSize, maxTextureSize, 8, maxTextureSize*4, CGImageGetColorSpace(image.CGImage), kCGImageAlphaPremultipliedLast);
CGContextDrawImage(textureContext, CGRectMake(0, maxTextureSize-size.height, size.width, size.height), image.CGImage);
CGContextRelease(textureContext);
// ...done creating the texture data
[EAGLContext setCurrentContext:context];
glGenTextures(1, &textureToView);
glBindTexture(GL_TEXTURE_2D, textureToView);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, maxTextureSize, maxTextureSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, textureData);
// free texture data which is by now copied into the GL context
free(textureData);
Each of the texture takes up about 8MB memory, which is unacceptable for an iPhone/iPad app. Could anyone tell me how can I compress the texture to reduce the memory. I'm a complete newbie to OpenGL.
Any help would be appreciated!
