iphone 压缩图片到指定的大小

1.本文摘自：http://www.cocoachina.com/bbs/read.php?tid-20940.html

 

#import <Foundation/Foundation.h> @interface UIImage (UIImageExt) - (UIImage*)imageByScalingAndCroppingForSize:(CGSize)targetSize; @end

复制代码 #import "UIImageExt.h" @implementation UIImage (UIImageExt) - (UIImage*)imageByScalingAndCroppingForSize:(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 > heightFactor)             scaleFactor = widthFactor; // scale to fit height         else             scaleFactor = heightFactor; // scale to fit width         scaledWidth  = width * scaleFactor;         scaledHeight = height * scaleFactor;                  // center the image         if (widthFactor > heightFactor)         {             thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;         }         else             if (widthFactor < heightFactor)             {                 thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;             }     }                UIGraphicsBeginImageContext(targetSize); // this will crop          CGRect thumbnailRect = CGRectZero;     thumbnailRect.origin = thumbnailPoint;     thumbnailRect.size.width  = scaledWidth;     thumbnailRect.size.height = scaledHeight;          [sourceImage drawInRect:thumbnailRect];          newImage = UIGraphicsGetImageFromCurrentImageContext();     if(newImage == nil)         NSLog(@"could not scale image");          //pop the context to get back to the default     UIGraphicsEndImageContext();     return newImage; } @end