【iOS】根据尺寸和比例缩放图片

根据尺寸

//根据指定尺寸缩放图片 -(UIImage *)imageCompressWithSize:(CGSize)size { **// UIGraphicsBeginImageContext(size); ///<用这个失真** UIGraphicsBeginImageContextWithOptions(size, NO, 0.0); ///<用这个不失真 [self drawInRect:CGRectMake(0, 0, size.width, size.height)]; UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return newImage; }

之前用模拟器跑是没有问题，但是在真机运行时用这个方法缩小的图片过于模糊，最后发现使用UIGraphicsBeginImageContext(size);方法会造成失真，换成UIGraphicsBeginImageContextWithOptions(size, NO, 0.0); 就可以

根据比例缩放

//根据指定比例缩放图片 -(UIImage *)imageCompressWithScale:(CGFloat)scale { CGSize size = self.size; CGFloat width = size.width; CGFloat height = size.height; CGFloat scaleWidth = width*scale; CGFloat scaleHeight = height*scale; UIGraphicsBeginImageContextWithOptions(CGSizeMake(scaleWidth, scaleHeight), NO, 0.0); ///<用这个不失真 [self drawInRect:CGRectMake(0, 0, scaleWidth, scaleHeight)]; UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return newImage; }