CS50 Week4无滤镜模糊函数异常求助：编译正常但模糊效果错误

我花了几天时间排查这个Blur函数的问题，它能正常编译，但图像模糊效果异常。我怀疑是数值或公式出错，反复检查数小时仍未找到问题。

本次作业要求使用3×3模糊框实现图像模糊：将模糊框内有效（在图像边界内）像素的RGB值求和，除以有效像素数量，再将模糊后的值赋值给图像。

但我生成的模糊图像完全无法分辨原有内容，我参考过其他模糊函数的实现，也多次从零重写代码尝试不同变体，但都无效。以下代码是我认为最接近正确实现的版本，恳请各位帮忙排查问题。

// Blur image
void blur(int height, int width, RGBTRIPLE image[height][width])
{    // create image copy for holding modifies RGB values
     RGBTRIPLE copy[height][width];
     for(int i = 0; i < height; i++)
     {
         for (int j = 0; j < width; j++)
         {
              copy[i][j] = image[i][j];
         }
     }
     // setting variable for holding sum of blur box RGB values
     float blurred = 0.0;
     float blurgreen = 0.0;
     float blurblue = 0.0;
     // setting counter for valid blur box pixels
     float validpixels = 0.0;
     // looping through image rows
     for( int i = 0; i < height; i++)
     {   // looping through image columns
         for(int j = 0; j < width; j++)
         {   // looping through blur box rows
             for(int r = -1; r < 2; r++)
             {   //looping through blur box columns
                 for(int c = -1; c < 2; c++)
                 {   // counting only valid blur-box pixels(inside image boundaries)
                     if(i + c >= 0 && j + r >= 0 && i + c < height && j + r < width)
                     {  // storing total of blur box RGB values
                        blurred += copy[i + c][j + r].rgbtRed;
                        blurgreen += copy[i + c][j + r].rgbtGreen;
                        blurblue += copy[i + c][j + r].rgbtBlue;
                        // counting valid pixels total
                        validpixels ++;
                     }
                 }
             }
               // calculate RGB  blurred values and assigning them to image copy
               copy[i][j].rgbtRed = round(blurred / validpixels);
               copy[i][j].rgbtGreen = round(blurgreen / validpixels);
               copy[i][j].rgbtBlue = round(blurblue / validpixels);
         }
     }
     //giving blur values back to image
     for(int i = 0; i < height; i++)
     {
         for (int j = 0; j < width; j++)
         {
              image[i][j].rgbtRed = copy[i][j].rgbtRed;
              image[i][j].rgbtGreen = copy[i][j].rgbtGreen;
              image[i][j].rgbtBlue = copy[i][j].rgbtBlue;
         }
     }
    return;
}

内容的提问来源于stack exchange，提问作者Nico