Render a layer to an image with scalefactor

gistfile1.txt

    dispatch_async(dispatch_get_main_queue(), ^{
        previewToSave = nil;
        CGSize screenSize = self.view.bounds.size;
        float scaleFactor = 0.2;
        const size_t originalWidth = screenSize.width * scaleFactor;
        const size_t originalHeight = screenSize.height * scaleFactor;

        CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
        CGContextRef ctx = CGBitmapContextCreate(nil, originalWidth, originalHeight, 8, 4*(int)originalWidth, colorSpaceRef, kCGImageAlphaPremultipliedLast);
        if (ctx != nil) {
            CGContextSetShouldAntialias(ctx, NO);
            CGContextSetAllowsAntialiasing(ctx, NO);
            CGContextSetInterpolationQuality(ctx, kCGInterpolationMedium);
            
            CGContextTranslateCTM(ctx, 0, originalHeight);
            CGContextScaleCTM(ctx, scaleFactor, -1 * scaleFactor);
            
            [aView.layer renderInContext:ctx];
            CGImageRef cgImage = CGBitmapContextCreateImage(ctx);
            CGContextRelease(ctx);
            CGColorSpaceRelease(colorSpaceRef);
            
            previewToSave = [UIImage imageWithCGImage:cgImage];
            NSLog(@"%d, %d, %d", (int)previewToSave.size.width, (int)previewToSave.size.height, [UIImagePNGRepresentation(previewToSave) length]/1024);
            CGImageRelease(cgImage);
        }
    });