http://www.bit-101.com/blog/?p=1861

C:

  1. -(UIImage *) glToUIImage {

  2.     NSInteger myDataLength = 320 * 480 * 4;

  4. // allocate array and read pixels into it.

  5.     GLubyte *buffer = (GLubyte *) malloc(myDataLength);

  6.     glReadPixels(0, 0, 320, 480, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

  8. // gl renders "upside down" so swap top to bottom into new array.

  9. // there's gotta be a better way, but this works.

  10.     GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);

  11. for(int y = 0; y <480; y++)

  12. {

  13. for(int x = 0; x <320 * 4; x++)

  14. {

  15.             buffer2[(479 - y) * 320 * 4 + x] = buffer[y * 4 * 320 + x];

  16. }

  17. }

  19. // make data provider with data.

  20.     CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, NULL);

  22. // prep the ingredients

  23. int bitsPerComponent = 8;

  24. int bitsPerPixel = 32;

  25. int bytesPerRow = 4 * 320;

  26.     CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();

  27.     CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;

  28.     CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;

  30. // make the cgimage

  31.     CGImageRef imageRef = CGImageCreate(320, 480, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);

  33. // then make the uiimage from that

  34.     UIImage *myImage = [UIImage imageWithCGImage:imageRef];

  35. return myImage;

  36. }

  38. -(void)captureToPhotoAlbum {

  39.     UIImage *image = [self glToUIImage];

  40.     UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);

  41. }