（IOS）获得灰度图

+ (UIImage*)covertToGrayImageFromImage:(UIImage*)sourceImage

{

    intwidth = sourceImage.size.width;

    intheight = sourceImage.size.height;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();

    CGContextRefcontext =CGBitmapContextCreate(nil,width,height,8,0,colorSpace,kCGImageAlphaNone);

    CGColorSpaceRelease(colorSpace);

    if(context ==NULL) {

        returnnil;

    }

    CGContextDrawImage(context,CGRectMake(0,0, width, height), sourceImage.CGImage);

    CGImageRefcontextRef =CGBitmapContextCreateImage(context);

    UIImage*grayImage = [UIImageimageWithCGImage:contextRef];

    CGContextRelease(context);

    CGImageRelease(contextRef);

    returngrayImage;

}