Cleaning up PSET4 Blur

Question

I have successfully finished the blur effect on PSET4.

Here is a small smattering of the code

 if(i - 1 >= 0 && j - 1 >= 0)
                {
                    red += OgImage[i-1][j-1].rgbtRed;
                    blue += OgImage[i-1][j-1].rgbtBlue;
                    green += OgImage[i-1][j-1].rgbtGreen;
                    
                    Divide++;
                }
                if(i - 1 >= 0 && j >= 0)
                {
                    red += OgImage[i-1][j].rgbtRed;
                    blue += OgImage[i-1][j].rgbtBlue;
                    green += OgImage[i-1][j].rgbtGreen;
                    
                    Divide++;
                }
                if(i - 1 >= 0 && j + 1 < width)
                {
                    red += OgImage[i-1][j+1].rgbtRed;
                    blue += OgImage[i-1][j+1].rgbtBlue;
                    green += OgImage[i-1][j+1].rgbtGreen;
                    
                    Divide++;
                }
                if(i >= 0 && j - 1 >= 0)
                {
                    red += OgImage[i][j-1].rgbtRed;
                    blue += OgImage[i][j-1].rgbtBlue;
                    green += OgImage[i][j-1].rgbtGreen;
                    
                    Divide++;
                }

etc...

It feels like there is probably some better way of doing this without writing out all this code though? My code passed all the verifications and works as intended. But is there some better way of creating edge of the image detection? He talked a lot about recursion in some of the previous lectures, does this situation lend itself to recursion or some other technique?

Answer 1

You can loop over the inner 3 by 3 grid and add a condition that covers all cases. Here's my code for the same section of blur.

for (int k = i - 1; k < i + 2; k++)
{
    for (int l = j - 1; l < j + 2; l++)
    {
        if (l >= 0 && l < width && k >= 0 && k < height)
        {
            sumred += image[k][l].rgbtRed;
            sumgrn += image[k][l].rgbtGreen;
            sumblu += image[k][l].rgbtBlue;

            pixelcount++; // same as your divide
        }
    }
}

Answer 2

Actually there are several ways of achieving blur. Heck you only need a single conditional statement to check if a pixel is valid or not.

In your implementation, it seems like you wrote an iterative solution(for loops) to do summation of pixels (check if they are valid using lot of conditional statements !). This can also be done using recursion to get final summation value