CS50 pset4, I have problems with getting the blur filter to work

Question

So basically what I did was, first I started off with the row above and then the relevant row and then the row below. I created a for loop which would run across the row 3 times.

My code looks like this, After editing once again,

// Blur image
void blur(int height, int width, RGBTRIPLE image[height][width])
{
    float temp[height][width][3];
    for (int i = 0; i < height; i++)
    {
        for (int j = 0; j < width; j++)
        {
            long sumRed = 0, sumBlue = 0, sumGreen = 0;
            int pixCount = 0;
            //top row
            for (int k = j - 1; k <= j + 1; k++)
            {
                if (i - 1 >= 0 && (k >= 0 && k < width))
                {
                    sumRed += (long)image[i-1][k].rgbtRed;
                    sumBlue += (long)image[i-1][k].rgbtBlue;
                    sumGreen += (long)image[i-1][k].rgbtGreen;
                    pixCount++;
                }
            }
           //relevant row
            for (int k = j - 1; k <= j + 1; k++)
            {
                 if (i >= 0 && (k >=0 && k < width))
                {
                    sumRed += (long)image[i][k].rgbtRed;
                    sumBlue += (long)image[i][k].rgbtBlue;
                    sumGreen += (long)image[i][k].rgbtGreen;
                    pixCount++;
                }
            }
            //bottom row
            for (int k = j - 1; k <= j + 1; k++)
            {
                 if (i + 1 < height && (k >= 0 && k < width))
                {
                    sumRed += (long)image[i+1][k].rgbtRed;
                    sumBlue += (long)image[i+1][k].rgbtBlue;
                    sumGreen += (long)image[i+1][k].rgbtGreen;
                    pixCount++;
                }
            }
            temp[i][j][0] = round(sumRed / pixCount);
            temp[i][j][1] = round(sumBlue / pixCount);
            temp[i][j][2] = round(sumGreen / pixCount);
        }
    }
    for (int i = 0; i < height; i++)
    {
        for (int j = 0; j < width; j++)
        {
            image[i][j].rgbtRed = temp[i][j][0];
            image[i][j].rgbtBlue = temp[i][j][1];
            image[i][j].rgbtGreen = temp[i][j][2];
        }
    }
    return;
}

And then when I run check 50 I get some errors.

So basically What I think happens there is the values doesn't get rounded off correctly. It misses by a slight error. Can someone help me. Thank you so much.

Answer 1

When you divided here: image[i][j].rgbtRed = (sumRed / pixCount); you'll problably get a decimal point result. The problem is that working with int variables will result in a truncated result, the decimal point will be erased, no mather if it's ,001 or ,999. you have to think a way to get around it.

Also you have to think that when taking the values from the surroundings pixels, some of them will be already changed so the result will be diferent than with the original ones. Think in how you could solve that.

Lastly, in your width loops your condition to stop is when x < with-1. Why is that?