海神

  //
  // UIImage-Extensions.h
  //
  // Created by Hardy Macia on 7/1/09.
  // Copyright 2009 Catamount Software. All rights reserved.
  //
  #import <Foundation/Foundation.h>

  @interface UIImage (CS_Extensions)
  - (UIImage *)imageAtRect:(CGRect)rect;
  - (UIImage *)imageByScalingProportionallyToMinimumSize:(CGSize)targetSize;
  - (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize;
  - (UIImage *)imageByScalingToSize:(CGSize)targetSize;
  - (UIImage *)imageRotatedByRadians:(CGFloat)radians;
  - (UIImage *)imageRotatedByDegrees:(CGFloat)degrees;

  @end;

  //
  // UIImage-Extensions.m
  //
  // Created by Hardy Macia on 7/1/09.
  // Copyright 2009 Catamount Software. All rights reserved.
  //

  #import "UIImage-Extensions.h"

  CGFloat DegreesToRadians(CGFloat degrees) {return degrees * M_PI / 180;};
  CGFloat RadiansToDegrees(CGFloat radians) {return radians * 180/M_PI;};

  @implementation UIImage (CS_Extensions)

  -(UIImage *)imageAtRect:(CGRect)rect
  { 
  CGImageRef imageRef = CGImageCreateWithImageInRect([self CGImage], rect);
  UIImage* subImage = [UIImage imageWithCGImage: imageRef];
  CGImageRelease(imageRef);

  return subImage;

  }

  - (UIImage *)imageByScalingProportionallyToMinimumSize:(CGSize)targetSize {

  UIImage *sourceImage = self;
  UIImage *newImage = nil;

  CGSize imageSize = sourceImage.size;
  CGFloat width = imageSize.width;
  CGFloat height = imageSize.height;

  CGFloat targetWidth = targetSize.width;
  CGFloat targetHeight = targetSize.height;

  CGFloat scaleFactor = 0.0;
  CGFloat scaledWidth = targetWidth;
  CGFloat scaledHeight = targetHeight;

  CGPoint thumbnailPoint = CGPointMake(0.0,0.0);

  if (CGSizeEqualToSize(imageSize, targetSize) == NO) {

  CGFloat widthFactor = targetWidth / width;
  CGFloat heightFactor = targetHeight / height;

  if (widthFactor &gt; heightFactor) 
  scaleFactor = widthFactor;
  else
  scaleFactor = heightFactor;

  scaledWidth = width * scaleFactor;
  scaledHeight = height * scaleFactor;

  // center the image

  if (widthFactor &gt; heightFactor) {
  thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; 
  } else if (widthFactor &lt; heightFactor) {
  thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
  }
  }


  // this is actually the interesting part:

  UIGraphicsBeginImageContext(targetSize);

  CGRect thumbnailRect = CGRectZero;
  thumbnailRect.origin = thumbnailPoint;
  thumbnailRect.size.width = scaledWidth;
  thumbnailRect.size.height = scaledHeight;

  [sourceImage drawInRect:thumbnailRect];

  newImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();

  if(newImage == nil) NSLog(@"could not scale image");


  return newImage ;
  }

  - (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize {

  UIImage *sourceImage = self;
  UIImage *newImage = nil;

  CGSize imageSize = sourceImage.size;
  CGFloat width = imageSize.width;
  CGFloat height = imageSize.height;

  CGFloat targetWidth = targetSize.width;
  CGFloat targetHeight = targetSize.height;

  CGFloat scaleFactor = 0.0;
  CGFloat scaledWidth = targetWidth;
  CGFloat scaledHeight = targetHeight;

  CGPoint thumbnailPoint = CGPointMake(0.0,0.0);

  if (CGSizeEqualToSize(imageSize, targetSize) == NO) {

  CGFloat widthFactor = targetWidth / width;
  CGFloat heightFactor = targetHeight / height;

  if (widthFactor &lt; heightFactor) 
  scaleFactor = widthFactor;
  else
  scaleFactor = heightFactor;

  scaledWidth = width * scaleFactor;
  scaledHeight = height * scaleFactor;

  // center the image

  if (widthFactor &lt; heightFactor) {
  thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; 
  } else if (widthFactor &gt; heightFactor) {
  thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
  }
  }


  // this is actually the interesting part:

  UIGraphicsBeginImageContext(targetSize);

  CGRect thumbnailRect = CGRectZero;
  thumbnailRect.origin = thumbnailPoint;
  thumbnailRect.size.width = scaledWidth;
  thumbnailRect.size.height = scaledHeight;

  [sourceImage drawInRect:thumbnailRect];

  newImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();

  if(newImage == nil) NSLog(@"could not scale image");


  return newImage ;
  }

  - (UIImage *)imageByScalingToSize:(CGSize)targetSize {

  UIImage *sourceImage = self;
  UIImage *newImage = nil;

  // CGSize imageSize = sourceImage.size;
  // CGFloat width = imageSize.width;
  // CGFloat height = imageSize.height;

  CGFloat targetWidth = targetSize.width;
  CGFloat targetHeight = targetSize.height;

  // CGFloat scaleFactor = 0.0;
  CGFloat scaledWidth = targetWidth;
  CGFloat scaledHeight = targetHeight;

  CGPoint thumbnailPoint = CGPointMake(0.0,0.0);

  // this is actually the interesting part:

  UIGraphicsBeginImageContext(targetSize);

  CGRect thumbnailRect = CGRectZero;
  thumbnailRect.origin = thumbnailPoint;
  thumbnailRect.size.width = scaledWidth;
  thumbnailRect.size.height = scaledHeight;

  [sourceImage drawInRect:thumbnailRect];

  newImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();

  if(newImage == nil) NSLog(@"could not scale image");


  return newImage ;
  }

  - (UIImage *)imageRotatedByRadians:(CGFloat)radians
  { return [self imageRotatedByDegrees:RadiansToDegrees(radians)];
  }

  - (UIImage *)imageRotatedByDegrees:(CGFloat)degrees 
  { 
  // calculate the size of the rotated view's containing box for our drawing space
  UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,self.size.width, self.size.height)];
  CGAffineTransform t = CGAffineTransformMakeRotation(DegreesToRadians(degrees));
  rotatedViewBox.transform = t;
  CGSize rotatedSize = rotatedViewBox.frame.size;
  [rotatedViewBox release];

  // Create the bitmap context
  UIGraphicsBeginImageContext(rotatedSize);
  CGContextRef bitmap = UIGraphicsGetCurrentContext();

  // Move the origin to the middle of the image so we will rotate and scale around the center.
  CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);

  // // Rotate the image context
  CGContextRotateCTM(bitmap, DegreesToRadians(degrees));

  // Now, draw the rotated/scaled image into the context
  CGContextScaleCTM(bitmap, 1.0, -1.0);
  CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2, self.size.width, self.size.height), [self CGImage]);

  UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  return newImage;

  }

  @end;