Blurring an image.bmp with "box blur" technique in C

Question

So in this project , I need to take an image.bmp file and blur it using "box blur".

The instructions for Box Blurring as follows:

For this problem, we’ll use the “box blur,” which works by taking each pixel and, for each color value, giving it a new value by averaging the color values of neighboring pixels.

(example) The new value of each pixel would be the average of the values of all of the pixels that are within 1 row and column of the original pixel (forming a 3x3 box). For example, each of the color values for pixel 6 would be obtained by averaging the original color values of pixels 1, 2, 3, 5, 6, 7, 9, 10, and 11 (note that pixel 6 itself is included in the average). Likewise, the color values for pixel 11 would be be obtained by averaging the color values of pixels 6, 7, 8, 10, 11, 12, 14, 15 and 16.

For a pixel along the edge or corner, like pixel 15, we would still look for all pixels within 1 row and column: in this case, pixels 10, 11, 12, 14, 15, and 16.

Now I know my code is a bit long and amateur,but it is only because I am an amateur but I have come this far without any help:

void blur(int height, int width, RGBTRIPLE image[height][width])
{
    // iterate through every row
    for (int i = 0; i < height; i++) 
    {
        //for every column
        for (int j = 0; j < width; j++) 
        {
            int avRed = 0;
            int avGreen = 0;
            int avBlue = 0;
            
             // check if the current index is an index of an edge 
            if ((i == 0 && (j >= 0 && j <= width - 1)) 
                || ((i >= 0 && i <= height - 1) && j == 0) 
                || (i == height - 1 && (j >= 0 && j <= width - 1)) 
                || ((i >= 0 && i <= height -1) && j == width - 1))
            {
                // if it is : check if it is a corner
                if ((i == 0 && j == 0) 
                    || (i == 0 && j == width - 1) 
                    || (i == height - 1 && j == 0) 
                    || (i == height - 1 && j == width - 1)) 
                {
                    if (i == 0 && j == 0)
                    {
                        avRed = round((image[i][j].rgbtRed + image[i + 1][j].rgbtRed + image[i + 1][j + 1].rgbtRed + image[i][j + 1].rgbtRed) / 4.0);
                        avGreen = round((image[i][j].rgbtGreen + image[i + 1][j].rgbtGreen + image[i + 1][j + 1].rgbtGreen + image[i][j + 1].rgbtGreen) / 4.0);
                        avBlue = round((image[i][j].rgbtBlue + image[i + 1][j].rgbtBlue + image[i + 1][j + 1].rgbtBlue + image[i][j + 1].rgbtBlue) / 4.0);
                        image[i][j].rgbtRed = avRed;
                        image[i][j].rgbtGreen = avGreen;
                        image[i][j].rgbtBlue = avBlue;
                    }

                    if (i == 0 && j == width - 1)
                    {
                        avRed = round((image[i][j].rgbtRed + image[i +1 ][j].rgbtRed + image[i + 1][j - 1].rgbtRed + image[i][j - 1].rgbtRed) / 4.0);
                        avGreen = round((image[i][j].rgbtGreen + image[i + 1][j].rgbtGreen + image[i + 1][j - 1].rgbtGreen + image[i][j - 1].rgbtGreen) / 4.0);
                        avBlue = round((image[i][j].rgbtBlue + image[i + 1][j].rgbtBlue + image[i + 1][j - 1].rgbtBlue + image[i][j - 1].rgbtBlue) / 4.0);
                        image[i][j].rgbtRed = avRed;
                        image[i][j].rgbtGreen = avGreen;
                        image[i][j].rgbtBlue = avBlue;
                    }

                    if(i == height - 1 && j == 0)
                    {
                        avRed = round((image[i][j].rgbtRed + image[i - 1][j].rgbtRed + image[i - 1][j + 1].rgbtRed + image[i][j + 1].rgbtRed) / 4.0);
                        avGreen= round((image[i][j].rgbtGreen + image[i - 1][j].rgbtGreen + image[i - 1][j + 1].rgbtGreen + image[i][j + 1].rgbtGreen) / 4.0);
                        avRed = round((image[i][j].rgbtBlue + image[i - 1][j].rgbtBlue + image[i - 1][j + 1].rgbtBlue + image[i][j + 1].rgbtBlue) / 4.0);
                        image[i][j].rgbtRed = avRed;
                        image[i][j].rgbtGreen = avGreen;
                        image[i][j].rgbtBlue = avBlue;
                    }

                    if (i == height - 1 && j == width - 1)
                    {
                        avRed = round((image[i][j].rgbtRed + image[i - 1][j].rgbtRed + image[i - 1][j - 1].rgbtRed + image[i][j - 1].rgbtRed) / 4.0);
                        avGreen = round((image[i][j].rgbtGreen + image[i - 1][j].rgbtGreen + image[i - 1][j - 1].rgbtGreen + image[i][j - 1].rgbtGreen) / 4.0);
                        avBlue = round((image[i][j].rgbtBlue + image[i - 1][j].rgbtBlue + image[i - 1][j - 1].rgbtBlue + image[i][j - 1].rgbtBlue) / 4.0);
                        image[i][j].rgbtRed = avRed;
                        image[i][j].rgbtGreen = avGreen;
                        image[i][j].rgbtBlue = avBlue;
                    }
                }
                else // if it is not a corner index
                {
                    if (i == 0 && (j >= 1 && j <= width - 2))
                    {
                        avRed = round((image[i][j].rgbtRed + image[i][j - 1].rgbtRed + image[i][j + 1].rgbtRed + image[i + 1][j].rgbtRed + image[i + 1][j - 1].rgbtRed + image[i + 1][j + 1].rgbtRed) / 6.0);
                        avGreen = round((image[i][j].rgbtGreen + image[i][j - 1].rgbtGreen + image[i][j + 1].rgbtGreen + image[i + 1][j].rgbtGreen + image[i + 1][j - 1].rgbtGreen + image[i + 1][j + 1].rgbtGreen) / 6.0);
                        avBlue = round((image[i][j].rgbtBlue + image[i][j - 1].rgbtBlue + image[i][j + 1].rgbtBlue + image[i + 1][j].rgbtBlue + image[i + 1][j - 1].rgbtBlue + image[i + 1][j + 1].rgbtBlue) / 6.0);
                        image[i][j].rgbtRed = avRed;
                        image[i][j].rgbtGreen = avGreen;
                        image[i][j].rgbtBlue = avBlue;
                    }

                    if ((i >= 1 && i <= height - 2) && j == 0)
                    {
                        avRed = round((image[i][j].rgbtRed + image[i - 1][j].rgbtRed + image[i + 1][j].rgbtRed + image[i][j + 1].rgbtRed + image[i - 1][j + 1].rgbtRed + image[i + 1][j + 1].rgbtRed) / 6.0);
                        avGreen = round((image[i][j].rgbtGreen + image[i - 1][j].rgbtGreen + image[i + 1][j].rgbtGreen + image[i][j + 1].rgbtGreen + image[i - 1][j + 1].rgbtGreen + image[i + 1][j + 1].rgbtGreen) / 6.0);
                        avBlue = round((image[i][j].rgbtBlue + image[i - 1][j].rgbtBlue + image[i + 1][j].rgbtBlue + image[i][j + 1].rgbtBlue + image[i - 1][j + 1].rgbtBlue + image[i + 1][j + 1].rgbtBlue) / 6.0);
                        image[i][j].rgbtRed = avRed;
                        image[i][j].rgbtGreen = avGreen;
                        image[i][j].rgbtBlue = avBlue;
                    }

                    if (i == height - 1 && (j >= 1 && j <= width - 2))
                    {
                        avRed = round((image[i][j].rgbtRed + image[i - 1][j].rgbtRed + image[i][j - 1].rgbtRed + image[i][j + 1].rgbtRed + image[i - 1][j + 1].rgbtRed + image[i - 1][j - 1].rgbtRed) / 6.0);
                        avGreen = round((image[i][j].rgbtGreen + image[i - 1][j].rgbtGreen + image[i][j - 1].rgbtGreen + image[i][j + 1].rgbtGreen + image[i - 1][j + 1].rgbtGreen + image[i - 1][j - 1].rgbtGreen) / 6.0);
                        avBlue = round((image[i][j].rgbtBlue + image[i - 1][j].rgbtBlue + image[i][j - 1].rgbtBlue + image[i][j + 1].rgbtBlue + image[i - 1][j + 1].rgbtBlue + image[i - 1][j - 1].rgbtBlue) / 6.0);
                        image[i][j].rgbtRed = avRed;
                        image[i][j].rgbtGreen = avGreen;
                        image[i][j].rgbtBlue = avBlue;
                    }

                    if ((i >= 1 && i <= height -2) && j == width - 1)
                    {
                        avRed = round((image[i][j].rgbtRed + image[i - 1][j].rgbtRed + image[i + 1][j].rgbtRed + image[i][j - 1].rgbtRed + image[i - 1][j - 1].rgbtRed + image[i + 1][j - 1].rgbtRed) / 6.0);
                        avGreen = round((image[i][j].rgbtGreen + image[i - 1][j].rgbtGreen + image[i + 1][j].rgbtGreen + image[i][j - 1].rgbtGreen + image[i - 1][j - 1].rgbtGreen + image[i + 1][j - 1].rgbtGreen) / 6.0);
                        avBlue = round((image[i][j].rgbtBlue + image[i - 1][j].rgbtBlue + image[i + 1][j].rgbtBlue + image[i][j - 1].rgbtBlue + image[i - 1][j - 1].rgbtBlue + image[i + 1][j - 1].rgbtBlue) / 6.0);
                        image[i][j].rgbtRed = avRed;
                        image[i][j].rgbtGreen = avGreen;
                        image[i][j].rgbtBlue = avBlue;
                    }
                }
            }
            else // if it is not an index of an edge at all
            {
                avRed = round(((image[i - 1][j - 1].rgbtRed) + (image[i - 1][j].rgbtRed) + (image[i - 1][j + 1].rgbtRed) + (image[i][j - 1].rgbtRed) + (image[i][j].rgbtRed) + (image[i][j + 1].rgbtRed) + (image[i + 1][j - 1].rgbtRed) + (image[i + 1][j].rgbtRed) + (image[i + 1][j + 1].rgbtRed)) / 9.0);
                avGreen = round(((image[i - 1][j - 1].rgbtGreen) + (image[i - 1][j].rgbtGreen) + (image[i - 1][j + 1].rgbtGreen) + (image[i][j - 1].rgbtGreen) + (image[i][j].rgbtGreen) + (image[i][j + 1].rgbtGreen) + (image[i + 1][j - 1].rgbtGreen) + (image[i + 1][j].rgbtGreen) + (image[i + 1][j + 1].rgbtGreen)) / 9.0);
                avBlue = round(((image[i - 1][j - 1].rgbtBlue) + (image[i - 1][j].rgbtBlue) + (image[i - 1][j + 1].rgbtBlue) + (image[i][j - 1].rgbtBlue) + (image[i][j].rgbtBlue) + (image[i][j + 1].rgbtBlue) + (image[i + 1][j - 1].rgbtBlue) + (image[i + 1][j].rgbtBlue) + (image[i + 1][j + 1].rgbtBlue)) / 9.0);
                image[i][j].rgbtRed = avRed;
                image[i][j].rgbtGreen = avGreen;
                image[i][j].rgbtBlue = avBlue;
            }    
        }
    } 
    return;
}

Now at this point, program somewhat blurs the image, but not for the right amount. When I test it via cs50's pre-set test cases, my RGB ratios are correct for corner indexes, but off for all the others. Why that might be happening?

You must make a new image and copy it onto the original afterwards. Otherwise you will be averaging from some of the pixels that have already been averaged. — Weather Vane, Sep 11 '21 at 18:49
Style suggestion: when you reference something like `image[i][j]` repeatedly, give it a meaningful name. Something like `RGBTRIPLE pixel = image[i][j];`. This will lead to much easier code to work with. — Chris, Sep 11 '21 at 19:49
@Chris Thank you for your advice and edit. As a beginner , any help is much appreciated. — BayLingual, Sep 11 '21 at 19:52
You're welcome. Generally, if you find yourself using copy and paste, there's probably a better way. Also, if you have multiple `if`s in a row that are all exclusive, you probably forgot some `else`s. — Chris, Sep 11 '21 at 20:22

score 1 · Accepted Answer · answered Jan 14 '22 at 14:49

first make shure to copy the orignal image's pixels into another varial of type RGBTRIPLE pixel by pixel using forloop if not the first blured pixel would affect the next pixel to abe blured then do you math.

this works for me!

    // Blur image
void blur(int height, int width, RGBTRIPLE image[height][width])
{
    RGBTRIPLE copy[height][width];
    for (int i = 0; i < width; i++)
    {
        for (int j = 0; j < height; j++)
        {
            copy[i][j] = image[i][j];
        }
    }
    for (int i = 0; i < height; i++)
    {
        for (int j = 0; j < width; j++)
        {
            // check for an edge
           if ((i == 0 && (j >= 0 && j <= width - 1))
                || ((i >= 0 && i <= height - 1) && j == 0)
                || (i == height - 1 && (j >= 0 && j <= width - 1))
                || ((i >= 0 && i <= height -1) && j == width - 1))
            {
                //check if it is a corner
                if ((i == 0 && j == 0)
                    || (i == 0 && j == width - 1)
                    || (i == height - 1 && j == 0)
                    || (i == height - 1 && j == width - 1))
                {
                    if (i == 0 && j == 0)
                    {
                        image[i][j].rgbtRed = (int) round((copy[i][j].rgbtRed + copy[i + 1][j].rgbtRed + copy[i + 1][j + 1].rgbtRed + copy[i][j + 1].rgbtRed) / 4.0);
                        image[i][j].rgbtGreen = (int) round((copy[i][j].rgbtGreen + copy[i + 1][j].rgbtGreen + copy[i + 1][j + 1].rgbtGreen + copy[i][j + 1].rgbtGreen) / 4.0);
                        image[i][j].rgbtBlue = (int) round((copy[i][j].rgbtBlue + copy[i + 1][j].rgbtBlue + copy[i + 1][j + 1].rgbtBlue + copy[i][j + 1].rgbtBlue) / 4.0);
                    }

                    if (i == 0 && j == width - 1)
                    {
                        image[i][j].rgbtRed = (int) round((copy[i][j].rgbtRed + copy[i +1 ][j].rgbtRed + copy[i + 1][j - 1].rgbtRed + copy[i][j - 1].rgbtRed) / 4.0);
                        image[i][j].rgbtGreen = (int) round((copy[i][j].rgbtGreen + copy[i + 1][j].rgbtGreen + copy[i + 1][j - 1].rgbtGreen + copy[i][j - 1].rgbtGreen) / 4.0);
                        image[i][j].rgbtBlue = (int) round((copy[i][j].rgbtBlue + copy[i + 1][j].rgbtBlue + copy[i + 1][j - 1].rgbtBlue + copy[i][j - 1].rgbtBlue) / 4.0);
                    }

                    if (i == height - 1 && j == 0)
                    {
                        image[i][j].rgbtRed = (int) round((copy[i][j].rgbtRed + copy[i - 1][j].rgbtRed + copy[i - 1][j + 1].rgbtRed + copy[i][j + 1].rgbtRed) / 4.0);
                        image[i][j].rgbtGreen = (int) round((copy[i][j].rgbtGreen + copy[i - 1][j].rgbtGreen + copy[i - 1][j + 1].rgbtGreen + copy[i][j + 1].rgbtGreen) / 4.0);
                        image[i][j].rgbtBlue = (int) round((copy[i][j].rgbtBlue + copy[i - 1][j].rgbtBlue + copy[i - 1][j + 1].rgbtBlue + copy[i][j + 1].rgbtBlue) / 4.0);
                    }

                    if (i == height - 1 && j == width - 1)
                    {
                        image[i][j].rgbtRed = (int) round((copy[i][j].rgbtRed + copy[i - 1][j].rgbtRed + copy[i - 1][j - 1].rgbtRed + copy[i][j - 1].rgbtRed) / 4.0);
                        image[i][j].rgbtGreen = (int) round((copy[i][j].rgbtGreen + copy[i - 1][j].rgbtGreen + copy[i - 1][j - 1].rgbtGreen + copy[i][j - 1].rgbtGreen) / 4.0);
                        image[i][j].rgbtBlue = (int) round((copy[i][j].rgbtBlue + copy[i - 1][j].rgbtBlue + copy[i - 1][j - 1].rgbtBlue + copy[i][j - 1].rgbtBlue) / 4.0);
                    }
                }
                // if not a corner index
                else
                {
                    if (i == 0 && (j >= 1 && j <= width - 2))
                    {
                        image[i][j].rgbtRed = (int) round((copy[i][j].rgbtRed + copy[i][j - 1].rgbtRed + copy[i][j + 1].rgbtRed + copy[i + 1][j].rgbtRed + copy[i + 1][j - 1].rgbtRed + copy[i + 1][j + 1].rgbtRed) / 6.0);
                        image[i][j].rgbtGreen = (int) round((copy[i][j].rgbtGreen + copy[i][j - 1].rgbtGreen + copy[i][j + 1].rgbtGreen + copy[i + 1][j].rgbtGreen + copy[i + 1][j - 1].rgbtGreen + copy[i + 1][j + 1].rgbtGreen) / 6.0);
                        image[i][j].rgbtBlue = (int) round((copy[i][j].rgbtBlue + copy[i][j - 1].rgbtBlue + copy[i][j + 1].rgbtBlue + copy[i + 1][j].rgbtBlue + copy[i + 1][j - 1].rgbtBlue + copy[i + 1][j + 1].rgbtBlue) / 6.0);
                    }

                    if ((i >= 1 && i <= height - 2) && j == 0)
                    {
                        image[i][j].rgbtRed = (int) round((copy[i][j].rgbtRed + copy[i - 1][j].rgbtRed + copy[i + 1][j].rgbtRed + copy[i][j + 1].rgbtRed + copy[i - 1][j + 1].rgbtRed + copy[i + 1][j + 1].rgbtRed) / 6.0);
                        image[i][j].rgbtGreen = (int) round((copy[i][j].rgbtGreen + copy[i - 1][j].rgbtGreen + copy[i + 1][j].rgbtGreen + copy[i][j + 1].rgbtGreen + copy[i - 1][j + 1].rgbtGreen + copy[i + 1][j + 1].rgbtGreen) / 6.0);
                        image[i][j].rgbtBlue = (int) round((copy[i][j].rgbtBlue + copy[i - 1][j].rgbtBlue + copy[i + 1][j].rgbtBlue + copy[i][j + 1].rgbtBlue + copy[i - 1][j + 1].rgbtBlue + copy[i + 1][j + 1].rgbtBlue) / 6.0);
                    }

                    if (i == height - 1 && (j >= 1 && j <= width - 2))
                    {
                        image[i][j].rgbtRed = (int) round((copy[i][j].rgbtRed + copy[i - 1][j].rgbtRed + copy[i][j - 1].rgbtRed + copy[i][j + 1].rgbtRed + copy[i - 1][j + 1].rgbtRed + copy[i - 1][j - 1].rgbtRed) / 6.0);
                        image[i][j].rgbtGreen = (int) round((copy[i][j].rgbtGreen + copy[i - 1][j].rgbtGreen + copy[i][j - 1].rgbtGreen + copy[i][j + 1].rgbtGreen + copy[i - 1][j + 1].rgbtGreen + copy[i - 1][j - 1].rgbtGreen) / 6.0);
                        image[i][j].rgbtBlue = (int) round((copy[i][j].rgbtBlue + copy[i - 1][j].rgbtBlue + copy[i][j - 1].rgbtBlue + copy[i][j + 1].rgbtBlue + copy[i - 1][j + 1].rgbtBlue + copy[i - 1][j - 1].rgbtBlue) / 6.0);
                    }

                    if ((i >= 1 && i <= height -2) && j == width - 1)
                    {
                        image[i][j].rgbtRed = (int) round((copy[i][j].rgbtRed + copy[i - 1][j].rgbtRed + copy[i + 1][j].rgbtRed + copy[i][j - 1].rgbtRed + copy[i - 1][j - 1].rgbtRed + copy[i + 1][j - 1].rgbtRed) / 6.0);
                        image[i][j].rgbtGreen = (int) round((copy[i][j].rgbtGreen + copy[i - 1][j].rgbtGreen + copy[i + 1][j].rgbtGreen + copy[i][j - 1].rgbtGreen + copy[i - 1][j - 1].rgbtGreen + copy[i + 1][j - 1].rgbtGreen) / 6.0);
                        image[i][j].rgbtBlue = (int) round((copy[i][j].rgbtBlue + copy[i - 1][j].rgbtBlue + copy[i + 1][j].rgbtBlue + copy[i][j - 1].rgbtBlue + copy[i - 1][j - 1].rgbtBlue + copy[i + 1][j - 1].rgbtBlue) / 6.0);
                    }
                }
            }
            // for normal pixel no edge at all
            else
            {
                image[i][j].rgbtRed = (int) round(((copy[i - 1][j - 1].rgbtRed) + (copy[i - 1][j].rgbtRed) + (copy[i - 1][j + 1].rgbtRed) + (copy[i][j - 1].rgbtRed) + (copy[i][j].rgbtRed) + (copy[i][j + 1].rgbtRed) + (copy[i + 1][j - 1].rgbtRed) + (copy[i + 1][j].rgbtRed) + (copy[i + 1][j + 1].rgbtRed)) / 9.0);
                image[i][j].rgbtGreen = (int) round(((copy[i - 1][j - 1].rgbtGreen) + (copy[i - 1][j].rgbtGreen) + (copy[i - 1][j + 1].rgbtGreen) + (copy[i][j - 1].rgbtGreen) + (copy[i][j].rgbtGreen) + (copy[i][j + 1].rgbtGreen) + (copy[i + 1][j - 1].rgbtGreen) + (copy[i + 1][j].rgbtGreen) + (copy[i + 1][j + 1].rgbtGreen)) / 9.0);
                image[i][j].rgbtBlue = (int) round(((copy[i - 1][j - 1].rgbtBlue) + (copy[i - 1][j].rgbtBlue) + (copy[i - 1][j + 1].rgbtBlue) + (copy[i][j - 1].rgbtBlue) + (copy[i][j].rgbtBlue) + (copy[i][j + 1].rgbtBlue) + (copy[i + 1][j - 1].rgbtBlue) + (copy[i + 1][j].rgbtBlue) + (copy[i + 1][j + 1].rgbtBlue)) / 9.0);
            }

        }
    }

    return;
}

Blurring an image.bmp with "box blur" technique in C

1 Answers1