UIImage 按照指定宽度等比例裁切

//使用
UIImage *portraitImg = [info objectForKey:UIImagePickerControllerOriginalImage];
portraitImg = [Util reSizeImage:portraitImg WithWidth:1242];

//代码
//对image按照width缩放剪裁
+ (UIImage *)reSizeImage:(UIImage *)originImage WithWidth:(float)width{

float   scaleSize = width/originImage.size.width;

if (scaleSize < 1) {

UIGraphicsBeginImageContext(CGSizeMake(originImage.size.width * scaleSize, originImage.size.height * scaleSize));
[originImage drawInRect:CGRectMake(0, 0, originImage.size.width * scaleSize, originImage.size.height * scaleSize)];
UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();
return scaledImage;

}
return originImage;
}