一个图片缩放和裁剪的例子

#import <UIKit/UIKit.h>

@interface UIImage(extesion)
-(UIImage *)getFitSizeImage:(CGSize)size;
@end

#import "UIImageExtesion.h"

@implementation UIImage(extesion)
-(UIImage *)getFitSizeImage:(CGSize)size {

CGFloat scale = 1.0;

if ((self.size.width / self.size.height) > (size.width / size.height)) {
scale = size.height / self.size.height;
} else {
scale = size.width / self.size.width;
}

CGSize imgScaleSize = CGSizeMake(self.size.width * scale, self.size.height * scale);

CGRect rect = CGRectMake((size.width - imgScaleSize.width) / 2.0, (size.height - imgScaleSize.height) / 2.0, imgScaleSize.width, imgScaleSize.height);
UIGraphicsBeginImageContext(size);
[self drawInRect:rect];
UIImage *desImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return desImage;
}
@end