Thread: how can l make this shorter?

Since the only variation (apart from function name) is the first index when accessing elements of digital_image, pass that index as a second argument (of type int) to the function.

If you don't know how to pass more than one argument to a function, look it up. All basic textbooks and tutorials related to functions describe how.

Or pass the desired row-of-DIGIT_WIDTH-columns directly as the function's only argument.

Oh my!

Code:

// counts black pixels in row 1
 
int
row1Pixels(int digit_image[DIGIT_HEIGHT][DIGIT_WIDTH]) {
    int column, black_pixels;
    black_pixels = 0;
    for (column = 0; column < DIGIT_WIDTH; column++) {
        if (digit_image[1][column] == 1) {
            black_pixels = black_pixels + 1;
        }
    }
    return black_pixels;
}

// counts black pixels in all rows. This function is called 27 times, 
// but that's not a bad thing.
 
int countBlackPixels(int digit_image[DIGIT_HEIGHT][DIGIT_WIDTH], int row) {
    int column, black_pixels;
    black_pixels = 0;
    for (column = 0; column < DIGIT_WIDTH; column++) {
        if (digit_image[row][column] == 1) {
            black_pixels = black_pixels + 1;
        }
    }
    return black_pixels;
}

The calling function will increment the value of the variable row (which would be the value of the customary variable 'i', in the following for loop:

Code:

int blackPixelSum=0;
int i;
for(i=0;i<DIGIT_HEIGHT;i++) {
   blackPixelSum+=countBlackPixels(digit_image[DIGIT_HEIGHT][DIGIT_WIDTH], i);
}

So 'i' is i in the calling function, but in the countBlackPixels() function, 'i' becomes 'row'.

This isn't the only way to do this, but it's one good way to do it.