iOS 网络/本地 图片 按自定义比例缩放 不失真 方法

+ (CGRect )scaleImage:(UIImage *)image toSize:(CGRect)newSize
{
float actualHeight = image.size.height;
float actualWidth = image.size.width;
float imgRatio = actualWidth/actualHeight;
float maxRatio = newSize.size.width/newSize.size.height;

if(imgRatio!=maxRatio){
if(imgRatio < maxRatio){
imgRatio = newSize.size.height/ actualHeight;
actualWidth = imgRatio * actualWidth;
actualHeight = newSize.size.height;
}
else{
imgRatio = newSize.size.width / actualWidth;
actualHeight = imgRatio * actualHeight;
actualWidth = newSize.size.width;
}
}
CGRect rect = CGRectMake(0.0, 0.0, actualWidth, actualHeight);
return rect;
}
调用时候 rect的宽和高 就是所需要得新的图片大小