图像压缩

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- (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; }