How to Resize UIImage and Keep the Aspect Ratio

leothenerd 1:04 pm on December 21, 2009 | Answers: 1    
Tags: aspect (3), ratio (3), resize (3), uiimage (2)

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• leothenerd 1:04 pm on December 21, 2009
  

  
  - (UIImage *)scaleImage:(UIImage *) image maxWidth:(float) maxWidth maxHeight:(float) maxHeight
  {
    CGImageRef imgRef = image.CGImage;
    CGFloat width = CGImageGetWidth(imgRef);
    CGFloat height = CGImageGetHeight(imgRef);
  
    if (width <= maxWidth && height <= maxHeight)
    {
      return image;
    }
  
    CGAffineTransform transform = CGAffineTransformIdentity;
    CGRect bounds = CGRectMake(0, 0, width, height);
  
    if (width > maxWidth || height > maxHeight)
    {
      CGFloat ratio = width/height;
  
      if (ratio > 1)
      {
        bounds.size.width = maxWidth;
        bounds.size.height = bounds.size.width / ratio;
      }
      else
      {
        bounds.size.height = maxHeight;
        bounds.size.width = bounds.size.height * ratio;
      }
    }
  
    CGFloat scaleRatio = bounds.size.width / width;
    UIGraphicsBeginImageContext(bounds.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextScaleCTM(context, scaleRatio, -scaleRatio);
    CGContextTranslateCTM(context, 0, -height);
    CGContextConcatCTM(context, transform);
    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
  
    UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
  
    return imageCopy;
  
  }