等比压缩图片的方法

- (UIImage*)imageEqualRatioScaledToSize:(CGSize)targetSize

{

UIImage *sourceImage = self;

UIImage *newImage = nil;

CGSize imageSize = sourceImage.size;

CGFloat srcWidth = imageSize.width;

CGFloat srcHeight = imageSize.height;

CGFloat targetWidth = targetSize.width;

CGFloat targetHeight = targetSize.height;

if (srcWidth <= targetWidth && srcHeight <= targetHeight) {

// 如果源图已经小于缩放尺寸，则返回源图

newImage = sourceImage;

} else {

// 如果源图长或宽大于缩放尺寸，则等比缩放

double scale = (double)targetWidth/srcWidth < (double)targetHeight/srcHeight ? (double)targetWidth/srcWidth : (double)targetHeight/srcHeight;

CGFloat scaleWidth = scale * srcWidth;

CGFloat scaleHeight = scale * srcHeight;

CGSize newSize = CGSizeMake(scaleWidth, scaleHeight);

UIGraphicsBeginImageContext(newSize);

CGRect thumbnailRect = CGRectMake(0, 0, scaleWidth, scaleHeight);

[sourceImage drawInRect:thumbnailRect];

newImage = UIGraphicsGetImageFromCurrentImageContext();

if(newImage == nil)

DLog(@"could not scale image");

UIGraphicsEndImageContext();

}

return newImage;

}