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[anthony_lynch15]

Hey guys,

Was having problems with this exact same issue.
This thread got me started down the road to the solution.
So I thought I'd share what I learned.

I didn't actually work out myself, but put it together from various forum threads and this little blog post in which a post by a guy called gamekozo in the comment section gave me the final piece of the puzzle.

This is the piece of code that takes the contents of the drawing view / painting view / EAGLView / GLView (whatever you want to call it), renders it.
Then turns it into a UIImage and passes it back to whereever it came from.

- (UIImage *) glToUIImage {
    NSInteger myDataLength = 320 * 480 * 4;
	
    // allocate array and read pixels into it.
    GLubyte *buffer = (GLubyte *) malloc(myDataLength);
    glReadPixels(0, 0, 320, 480, 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 <480; y++)
    {
        for(int x = 0; x <320 * 4; x++)
        {
            buffer2[(479 - y) * 320 * 4 + x] = buffer[y * 4 * 320 + x];
        }
    }
	
    // make data provider with data.
    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, NULL);
	
    // prep the ingredients
    int bitsPerComponent = 8;
    int bitsPerPixel = 32;
    int bytesPerRow = 4 * 320;
    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
	
   //xxxxxx This is the line of code that I found in multiple solutions throughout the web but doesn't deal with the transparency
   // CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
   //xxxxxx

   //*******This is the code I used to handle the tranparency!!!
   CGBitmapInfo bitmapInfo = kCGImageAlphaPremultipliedLast;
   //*******               

    CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
	
    // make the cgimage
    CGImageRef imageRef = CGImageCreate(320, 480, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
	
    // then make the uiimage from that
    UIImage *myImage = [UIImage imageWithCGImage:imageRef];
    return myImage;
}

The vital piece of code for being able to save the transparency/alpha properties of the GLView is the line:
CGBitmapInfo bitmapInfo = kCGImageAlphaPremultipliedLast;

You can use code like the following to save the image created from the GLView in the code above.
Below I create an UIImage which I then put the image rendered into.
Then save it to the Camera Roll / Photo Album

UIImage *viewImage = [self glToUIImage];
		
//code to write the image to the Photo Album
UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);

You can put the image into an ImageView over a background and then save the whole thing etc.

Hope that helps people and saves them a day of searching.

~Anthony