UIImage转为灰度图

转自：http://bj007.blog.51cto.com/1701577/541525

 

-(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; 
}

其中，CGColorSpaceCreateDeviceGray会创建一个设备相关的灰度颜色空间的引用。