iOS 图片处理为灰色 透明

-(UIImage*)getGrayImage:(UIImage*)sourceImage { int width = sourceImage.size.width; int height = sourceImage.size.height; CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray(); CGContextRef context = CGBitmapContextCreate (nil,width,height,8,0,colorSpace,kCGImageAlphaNone); CGColorSpaceRelease(colorSpace); if (context == NULL) { return nil; } CGContextDrawImage(context,CGRectMake(0, 0, width, height), sourceImage.CGImage); UIImage *grayImage = [UIImage imageWithCGImage:CGBitmapContextCreateImage(context)]; CGContextRelease(context); return grayImage; }