Can this switch statement be shortened?

Question

Could this switch statement be shortened? Is it proper way of doing this? It is a simple thing and I don't know if there is a sense to use switch.

This part of code iterates through an array to take value of intesivity of color(form 0 to about 10) and draw a square with this color using allegro library. So for 7 and more it will be black, for less it will be grey and for 1 it will be very light grey.

 for (int j = 0; j < 50; j++) {
    for (int i = 0; i < 50; i++) {
        int value = cells[i + j * 50];
        if(value > 0) {
            unsigned char color;
            switch (value) {
                case 1 :
                     color = 200;
                    break;
                case 2 :
                    color = 180;
                    break;
                case 3 :
                    color = 140;
                    break;
                case 4 :
                    color = 100;
                    break;
                case 5 :
                    color = 60;
                    break;
                case 6 :
                    color = 40;
                    break;
                case 7 :
                    color = 20;
                    break;
                default: color = 0;
            }
            al_draw_filled_rectangle(i * 8, 400 - (j * 8), i * 8 + 8, 400 - (j * 8 + 8),
                                     al_map_rgb(color, color, color));
        }
    }
}

Answer 1

You can use a lookup table instead of switch statement

static const unsigned char COLORS[] = { 0, 200, 180, 140, 100, 60, 40, 20 };

unsigned char color = 
  value >= 0 && value < sizeof COLORS / sizeof *COLORS ? COLORS[value] : 0;