Arbitrary rotation of a CGImage

7 réflexions au sujet de “Arbitrary rotation of a CGImage”

1. This kind of code snippet is a perfect fit for a gist: http://gist.github.com

2. It is now: http://gist.github.com/180812

3. Ping : NSCoriolisBlog » Blog Archive » Arbitrary rotation of a CGImage « Connor Denman's Blog

4. The code above was a great starting point, but did not work correctly in any of the tests I did. This repo contains a fixed version derived from the above code:
   https://github.com/JanX2/CreateRotateWriteCFImage

5. Ping : 9-slice scaling/stretching in the background, using Cocoa on iOS. | taking a bite into Apple

6. Here is the working version for everyone else that stumbles upon this awesome function but finds it to be broke like I did.

   
- (CGImageRef)CGImageRotatedByAngle:(CGImageRef)imgRef angle:(CGFloat)angle
{
CGFloat angleInRadians = angle * (M_PI / 180);
CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);

   CGRect imgRect = CGRectMake(0, 0, width, height);
   CGAffineTransform transform = CGAffineTransformMakeRotation(angleInRadians);
   CGRect rotatedRect = CGRectApplyAffineTransform(imgRect, transform);

   CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
   CGContextRef bmContext = CGBitmapContextCreate(NULL,
   rotatedRect.size.width,
   rotatedRect.size.height,
   8,
   0,
   colorSpace,
   kCGImageAlphaPremultipliedFirst);
   CGContextSetAllowsAntialiasing(bmContext, TRUE);
   CGContextSetInterpolationQuality(bmContext, kCGInterpolationNone);
   CGColorSpaceRelease(colorSpace);
   CGContextTranslateCTM(bmContext,
   +(rotatedRect.size.width/2),
   +(rotatedRect.size.height/2));
   CGContextRotateCTM(bmContext, angleInRadians);
   CGContextTranslateCTM(bmContext,
   -(rotatedRect.size.width/2),
   -(rotatedRect.size.height/2));
   CGContextDrawImage(bmContext,
   CGRectMake((rotatedRect.size.width-width)/2.0f,
   (rotatedRect.size.height-height)/2.0f,
   width,
   height),
   imgRef);

   CGImageRef rotatedImage = CGBitmapContextCreateImage(bmContext);
CFRelease(bmContext);
return rotatedImage;
}


7. Thanks for the snippet!

   Pure genius and exactly what I needed.