Here is a cleaned up version of Quakeboy’s code.
I tested it on iPad, and works just fine.
The improvements include:
- works with any size EAGLView
- works with retina display (point scale 2)
- replaced nested loop with memcpy
- cleaned up memory leaks
- saves the UIImage in the photoalbum as a bonus.
Use this as a method in your EAGLView:
-(void)snapUIImage
{
int s = 1;
UIScreen* screen = [ UIScreen mainScreen ];
if ( [ screen respondsToSelector:@selector(scale) ] )
s = (int) [ screen scale ];
const int w = self.frame.size.width;
const int h = self.frame.size.height;
const NSInteger myDataLength = w * h * 4 * s * s;
// allocate array and read pixels into it.
GLubyte *buffer = (GLubyte *) malloc(myDataLength);
glReadPixels(0, 0, w*s, h*s, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
// gl renders "upside down" so swap top to bottom into new array.
// there's gotta be a better way, but this works.
GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);
for(int y = 0; y < h*s; y++)
{
memcpy( buffer2 + (h*s - 1 - y) * w * 4 * s, buffer + (y * 4 * w * s), w * 4 * s );
}
free(buffer); // work with the flipped buffer, so get rid of the original one.
// make data provider with data.
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, NULL);
// prep the ingredients
int bitsPerComponent = 8;
int bitsPerPixel = 32;
int bytesPerRow = 4 * w * s;
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
// make the cgimage
CGImageRef imageRef = CGImageCreate(w*s, h*s, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
// then make the uiimage from that
UIImage *myImage = [ UIImage imageWithCGImage:imageRef scale:s orientation:UIImageOrientationUp ];
UIImageWriteToSavedPhotosAlbum( myImage, nil, nil, nil );
CGImageRelease( imageRef );
CGDataProviderRelease(provider);
CGColorSpaceRelease(colorSpaceRef);
free(buffer2);
}