iOS对图像进行尺寸压缩

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iOS Objective-C对图像进行压缩，最简单的就是对图像进行等比例缩小。代码如下：

- (UIImage*)scaleFromImage:(UIImage*)image scaledToSize:(CGSize)newSize{ CGSize imageSize = image.size; CGFloat width = imageSize.width; CGFloat height = imageSize.height;       if (width <= newSize.width && height <= newSize.height){  return image; }       if (width == 0 || height == 0){  return image; }       CGFloat widthFactor = newSize.width / width; CGFloat heightFactor = newSize.height / height; CGFloat scaleFactor = (widthFactor<heightFactor?widthFactor:heightFactor);       CGFloat scaledWidth = width * scaleFactor; CGFloat scaledHeight = height * scaleFactor; CGSize targetSize = CGSizeMake(scaledWidth,scaledHeight);          UIGraphicsBeginImageContext(targetSize);    [image drawInRect:CGRectMake(0,0,scaledWidth,scaledHeight)];    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();    return newImage;}

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