1.获取灰度图

 -(UIImage*)getGrayscale:(UIImage*)sourceImage
    {
      int width = sourceImage.size.width;
      int height = sourceImage.size.height;
      CGColorSpaceRef colorSpace =  CGColorSpaceCreateDeviceGray();
      CGContextRef context = CGBitmapContextCreate (nil,width,height,8,width,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;
}

2.计算模糊程度（小于500认为是模糊图，这个值可以自己看情况定义）

 double getImgBlurDegree(unsigned char* ImgdataGray, int nWidth, int nHeight)
{
  if(ImgdataGray == NULL || nWidth <= 4 || nHeight <= 4)
{
    return 0.0;
}
int row= nHeight;
int col= nWidth;
int widthstep=nWidth;
double S=0;
unsigned char* data  = ImgdataGray;
for(int x = 1;x<row-1;x+=2)
{
    unsigned char *pre_row=data +(x-1)*widthstep;
    unsigned char *cur_row=data +x*widthstep;
    unsigned char *nex_row=data +(x+1)*widthstep;
    int Sx,Sy;
    for(int y = 1;y<col-1;y+=2)
    {
        Sx=(int)pre_row[y+1]+2*(int)cur_row[y+1]+(int)nex_row[y+1]//一定要转为uchar
        -(int)pre_row[y-1]-2*(int)cur_row[y-1]-(int)nex_row[y-1];
        Sy=(int)nex_row[y-1]+2*(int)nex_row[y]+(int)nex_row[y+1]
        -(int)pre_row[y-1]-2*(int)pre_row[y]-(int)pre_row[y+1];  
        S+=Sx*Sx+Sy*Sy;  
    }  
} 
  return S/(row/2-2)/(col/2-2);  
}

使用

- (double)getImageDimValue:(UIImage *)sourceImage {
if (!sourceImage) {
    return 0;
}
UIImage *grayscale = [self getGrayscale:sourceImage];

CGImageRef imageRef = [grayscale CGImage];
CGFloat width = CGImageGetWidth(imageRef);
CGFloat height = CGImageGetHeight(imageRef);

CGDataProviderRef provider =  CGImageGetDataProvider(imageRef);
NSData* data = (id)CFBridgingRelease(CGDataProviderCopyData(provider));
uint8_t *grayscaleData = (uint8_t *)[data bytes];

return  getImgBlurDegree(grayscaleData, width, height);
}