cs50 filter(blur) assignment (pset4) - c

Question

I am doing a cs50 assignment filter(blur). i didnt do it really well but it is working. bluring all the pixels except the first row(north) and the final row (south) in the pic. and the corners of the picture are blured but the pixels after the corners the colors are really unusual. i dont know its the conditions or the the color changing that messed this up. so i can use another pair of eyes for finding the problem thank you
[click here to see the issues in detail]
void blur(int height, int width, RGBTRIPLE image[height][width])
{
RGBTRIPLE changed[height][width];
for(int i=0 ; i<=height-1 ;i++)
{
for(int j=0 ; j<=width-1 ; j++)
{
if(i==0) //main if north corners
{
if (j==0)
{
changed[i][j].rgbtRed =round( (image[i][j].rgbtRed + image[i][j+1].rgbtRed + image[i+1][j+1].rgbtRed + image[i+1][j].rgbtRed) /4);
changed[i][j].rgbtGreen = round((image[i][j].rgbtGreen + image[i][j+1].rgbtGreen + image[i+1][j+1].rgbtGreen + image[i+1][j].rgbtGreen) /4);
changed[i][j].rgbtBlue = round((image[i][j].rgbtBlue + image[i][j+1].rgbtBlue + image[i+1][j+1].rgbtBlue + image[i+1][j].rgbtBlue) /4);
}
else if(j==width-1)
{
changed[i][j].rgbtRed = round((image[i][j].rgbtRed + image[i][j-1].rgbtRed + image[i+1][j-1].rgbtRed + image[i+1][j].rgbtRed) /4);
changed[i][j].rgbtGreen = round( (image[i][j].rgbtGreen + image[i][j-1].rgbtGreen + image[i+1][j-1].rgbtGreen + image[i+1][j].rgbtGreen) /4);
changed[i][j].rgbtBlue = round( (image[i][j].rgbtBlue + image[i][j-1].rgbtBlue + image[i+1][j-1].rgbtBlue + image[i+1][j].rgbtBlue) /4);
}
}
else if(i==height-1) //main if south corners
{
if (j==0)
{
changed[i][j].rgbtRed = round( (image[i][j].rgbtRed + image[i-1][j].rgbtRed + image[i-1][j+1].rgbtRed + image[i][j+1].rgbtRed) /4);
changed[i][j].rgbtGreen = round( (image[i][j].rgbtGreen + image[i-1][j].rgbtGreen + image[i-1][j+1].rgbtGreen + image[i][j+1].rgbtGreen) /4);
changed[i][j].rgbtBlue = round((image[i][j].rgbtBlue + image[i-1][j].rgbtBlue + image[i-1][j+1].rgbtBlue + image[i][j+1].rgbtBlue) /4);
}
else if(j==width-1)
{
changed[i][j].rgbtRed = round ((image[i][j].rgbtRed + image[i-1][j].rgbtRed + image[i-1][j-1].rgbtRed + image[i][j-1].rgbtRed) /4);
changed[i][j].rgbtGreen = round ((image[i][j].rgbtGreen + image[i-1][j].rgbtGreen + image[i-1][j-1].rgbtGreen + image[i][j-1].rgbtGreen) /4);
changed[i][j].rgbtBlue = round ((image[i][j].rgbtBlue + image[i-1][j].rgbtBlue + image[i-1][j-1].rgbtBlue + image[i][j-1].rgbtBlue) /4);
}
}
else if(i>0 && i<height-1 && j==0) //main if left side
{
changed[i][j].rgbtRed = round((image[i][j].rgbtRed + image[i-1][j].rgbtRed + image[i-1][j+1].rgbtRed + image[i][j+1].rgbtRed + image[i+1][j+1].rgbtRed + image[i+1][j].rgbtRed) /6);
changed[i][j].rgbtGreen = round( (image[i][j].rgbtGreen + image[i-1][j].rgbtGreen + image[i-1][j+1].rgbtGreen + image[i][j+1].rgbtGreen + image[i+1][j+1].rgbtGreen + image[i+1][j].rgbtGreen) /6);
changed[i][j].rgbtBlue = round ((image[i][j].rgbtBlue + image[i-1][j].rgbtBlue + image[i-1][j+1].rgbtBlue + image[i][j+1].rgbtBlue + image[i+1][j+1].rgbtBlue + image[i+1][j].rgbtBlue) /6);
}
else if(i>0 && i<height-1 && j==width-1) //main if right side
{
changed[i][j].rgbtRed = round ((image[i][j].rgbtRed + image[i-1][j].rgbtRed + image[i-1][j-1].rgbtRed + image[i][j-1].rgbtRed + image[i+1][j-1].rgbtRed + image[i+1][j].rgbtRed) /6);
changed[i][j].rgbtGreen = round ((image[i][j].rgbtGreen + image[i-1][j].rgbtGreen + image[i-1][j-1].rgbtGreen + image[i][j-1].rgbtGreen + image[i+1][j-1].rgbtGreen + image[i+1][j].rgbtGreen) /6);
changed[i][j].rgbtBlue = round ((image[i][j].rgbtBlue + image[i-1][j].rgbtBlue + image[i-1][j-1].rgbtBlue + image[i][j-1].rgbtBlue + image[i+1][j-1].rgbtBlue + image[i+1][j].rgbtBlue) /6);
}
else if(i==0 && j>0 && j<width-1) //main if north side
{
changed[i][j].rgbtRed = round ((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 + image[i][j+1].rgbtRed) /6);
changed[i][j].rgbtGreen = round((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 + image[i][j+1].rgbtGreen) /6);
changed[i][j].rgbtBlue = round((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 + image[i][j+1].rgbtBlue) /6);
}
else if(i==height-1 && j>0 && j>width-1) //main if south side
{
changed[i][j].rgbtRed = round( (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 + image[i][j+1].rgbtRed) /6);
changed[i][j].rgbtGreen = round((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 + image[i][j+1].rgbtGreen) /6);
changed[i][j].rgbtBlue = round( (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 + image[i][j+1].rgbtBlue) /6);
}
else //other pixels in the middle
{
changed[i][j].rgbtRed = round ((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 + image[i][j+1].rgbtRed + image[i+1][j+1].rgbtRed + image[i+1][j].rgbtRed + image[i+1][j-1].rgbtRed) /9);
changed[i][j].rgbtGreen = round ((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 + image[i][j+1].rgbtGreen + image[i+1][j+1].rgbtGreen + image[i+1][j].rgbtGreen + image[i+1][j-1].rgbtGreen) /9);
changed[i][j].rgbtBlue = round( (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 + image[i][j+1].rgbtBlue + image[i+1][j+1].rgbtBlue + image[i+1][j].rgbtBlue + image[i+1][j-1].rgbtBlue) /9);
}
}
}
for (int i = 0 ;i<=height-1 ; i++)
{
for (int j = 0 ; j<=width-1 ; j++)
{
image[i][j]=changed[i][j];
}
}
return;
}

Answer 1

bluring all the pixels except the first row(north) and the final row (south) in the pic
If you go through the case discriminations with all those ifs and elses, you'll find that the code blocks that should handle the north and south edges between the corners are not entered after the preceding if(i==0) and if(i==height-1); indeed with that many cases that was easy to miss. You could move the code blocks or you could make the whole operation more concise, e. g.:
for (int i = 0; i < height; ++i)
for (int j = 0; j < width; ++j)
{
int r = 0, g = 0, b = 0, c = 0; // surrounding pixel color sums and count
for (int y = i-1; y <= i+1; ++y) if (0 <= y && y < height)
for (int x = j-1; x <= j+1; ++x) if (0 <= x && x < width)
r += image[y][x].rgbtRed,
g += image[y][x].rgbtGreen,
b += image[y][x].rgbtBlue,
++c;
// now compute the rounded averages
changed[i][j].rgbtRed = (r+c/2)/c;
changed[i][j].rgbtGreen = (g+c/2)/c;
changed[i][j].rgbtBlue = (b+c/2)/c;
}

Answer 2

This is the changed code
RGBTRIPLE changed[height][width];
for (int i = 0 ; i <= height - 1 ;i++)
{
for (int j = 0 ; j <= width - 1 ; j++)
{
//main if north side
if (i == 0 && j > 0 && j < width - 1 )
{
changed[i][j].rgbtRed = round((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 + image[i][j + 1].rgbtRed) / (6.0));
changed[i][j].rgbtGreen = round((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 + image[i][j + 1].rgbtGreen) / (6.0));
changed[i][j].rgbtBlue = round((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 + image[i][j + 1].rgbtBlue) / (6.0));
}
//main if south side
else if (i==height - 1 && j > 0 && j > width - 1)
{
changed[i][j].rgbtRed = round((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 + image[i][j + 1].rgbtRed) / (6.0));
changed[i][j].rgbtGreen = round((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 + image[i][j + 1].rgbtGreen) / (6.0));
changed[i][j].rgbtBlue = round((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 + image[i][j + 1].rgbtBlue) / (6.0));
}
//main if left side
else if (i > 0 && i < height - 1 && j == 0)
{
changed[i][j].rgbtRed = round((image[i][j].rgbtRed + image[i - 1][j].rgbtRed + image[i - 1][j + 1].rgbtRed + image[i][j + 1].rgbtRed + image[i + 1][j + 1].rgbtRed + image[i + 1][j].rgbtRed) / 6.0);
changed[i][j].rgbtGreen = round((image[i][j].rgbtGreen + image[i - 1][j].rgbtGreen + image[i - 1][j + 1].rgbtGreen + image[i][j + 1].rgbtGreen + image[i + 1][j + 1].rgbtGreen + image[i + 1][j].rgbtGreen) / 6.0);
changed[i][j].rgbtBlue = round((image[i][j].rgbtBlue + image[i - 1][j].rgbtBlue + image[i - 1][j + 1].rgbtBlue + image[i][j + 1].rgbtBlue + image[i + 1][j + 1].rgbtBlue + image[i + 1][j].rgbtBlue) / 6.0);
}
//main if right side
else if (i > 0 && i < height - 1 && j == width - 1)
{
changed[i][j].rgbtRed = round((image[i][j].rgbtRed + image[i - 1][j].rgbtRed + image[i - 1][j - 1].rgbtRed + image[i][j - 1].rgbtRed + image[i + 1][j - 1].rgbtRed + image[i + 1][j].rgbtRed) / 6.0);
changed[i][j].rgbtGreen = round((image[i][j].rgbtGreen + image[i - 1][j].rgbtGreen + image[i - 1][j - 1].rgbtGreen + image[i][j - 1].rgbtGreen + image[i + 1][j - 1].rgbtGreen + image[i + 1][j].rgbtGreen) / 6.0);
changed[i][j].rgbtBlue = round((image[i][j].rgbtBlue + image[i - 1][j].rgbtBlue + image[i - 1][j - 1].rgbtBlue + image[i][j - 1].rgbtBlue + image[i + 1][j - 1].rgbtBlue + image[i + 1][j].rgbtBlue) / 6.0);
}
//main if north corners
if (i == 0)
{
//north left corner
if (j == 0)
{
changed[i][j].rgbtRed = round((image[i][j].rgbtRed + image[i][j + 1].rgbtRed + image[i + 1][j + 1].rgbtRed + image[i + 1][j].rgbtRed) / 4.0);
changed[i][j].rgbtGreen = round((image[i][j].rgbtGreen + image[i][j + 1].rgbtGreen + image[i + 1][j + 1].rgbtGreen + image[i + 1][j].rgbtGreen) / 4.0);
changed[i][j].rgbtBlue = round((image[i][j].rgbtBlue + image[i][j + 1].rgbtBlue + image[i + 1][j + 1].rgbtBlue + image[i + 1][j].rgbtBlue) / 4.0);
}
//north left corner
else if (j == width - 1)
{
changed[i][j].rgbtRed = round((image[i][j].rgbtRed + image[i][j - 1].rgbtRed + image[i + 1][j - 1].rgbtRed + image[i + 1][j].rgbtRed) / 4.0);
changed[i][j].rgbtGreen = round((image[i][j].rgbtGreen + image[i][j - 1].rgbtGreen + image[i + 1][j - 1].rgbtGreen + image[i + 1][j].rgbtGreen) / 4.0);
changed[i][j].rgbtBlue = round((image[i][j].rgbtBlue + image[i][j - 1].rgbtBlue + image[i + 1][j - 1].rgbtBlue + image[i + 1][j].rgbtBlue) / 4.0);
}
}
//main if south corners
else if (i == height - 1)
{
//south right corner
if (j == 0)
{
changed[i][j].rgbtRed = round((image[i][j].rgbtRed + image[i - 1][j].rgbtRed + image[i - 1][j + 1].rgbtRed + image[i][j + 1].rgbtRed) / 4.0);
changed[i][j].rgbtGreen = round((image[i][j].rgbtGreen + image[i - 1][j].rgbtGreen + image[i - 1][j + 1].rgbtGreen + image[i][j + 1].rgbtGreen) / 4.0);
changed[i][j].rgbtBlue = round((image[i][j].rgbtBlue + image[i - 1][j].rgbtBlue + image[i - 1][j + 1].rgbtBlue + image[i][j + 1].rgbtBlue) / 4.0);
}
//south left corner
else if (j == width - 1)
{
changed[i][j].rgbtRed = round((image[i][j].rgbtRed + image[i - 1][j].rgbtRed + image[i - 1][j - 1].rgbtRed + image[i][j - 1].rgbtRed) / 4.0);
changed[i][j].rgbtGreen = round((image[i][j].rgbtGreen + image[i - 1][j].rgbtGreen + image[i - 1][j - 1].rgbtGreen + image[i][j - 1].rgbtGreen) / 4.0);
changed[i][j].rgbtBlue = round((image[i][j].rgbtBlue + image[i - 1][j].rgbtBlue + image[i - 1][j - 1].rgbtBlue + image[i][j - 1].rgbtBlue) / 4.0);
}
}
else //other pixels in the middle
{
changed[i][j].rgbtRed = round((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 + image[i][j + 1].rgbtRed + image[i + 1][j + 1].rgbtRed + image[i + 1][j].rgbtRed + image[i + 1][j - 1].rgbtRed) / (9.0));
changed[i][j].rgbtGreen = round((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 + image[i][j + 1].rgbtGreen + image[i + 1][j + 1].rgbtGreen + image[i + 1][j].rgbtGreen + image[i + 1][j - 1].rgbtGreen) / (9.0));
changed[i][j].rgbtBlue = round((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 + image[i][j + 1].rgbtBlue + image[i + 1][j + 1].rgbtBlue + image[i + 1][j].rgbtBlue + image[i + 1][j - 1].rgbtBlue) / (9.0));
}
}
}
//putting the changed color value in original image(applying the blue filter)
for (int i = 0 ; i <= height - 1 ; i++)
{
for (int j = 0 ; j <= width - 1 ; j++)
{
image[i][j] = changed[i][j];
}
}
return;