Hey everyone!

I'm having trouble understanding how the color and palette system works in the library.

Currently, I'm drawing a simple Pong game (using white for the elements and other simple drawing functions like line and rectangle).

However, I've created a simple palette with some shades of green that I want to use to simulate a color decay effect using the framebuffer.

My problem is that I can't change (and especially compare) the colors in the drawn framebuffer to know which color I need to "decay".

I don't understand the combined concept of being able to change the framebuffer and the color palette.

Could you please help me?
Thanks.

One question: for example, the code "getpixel(x, y)" returns a color or an index from the palette? If it's a color, this color can be different from the defined/default palette?

I think I understood: the library only works in terms of a palette index: it means that when I use putpixel, getpixel (or setcolor) they will work with an index that will use the color  (rgb) specified in the setpal function.

Hey guys, I also made a quick program to visualize the default doslike palette (it will be useful for future projects):

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <math.h>
#include <time.h>
#include "dos.h"
#define SCREEN_WIDTH        screenwidth()
#define SCREEN_HEIGHT       screenheight()
#define SQUARE_SIZE         15      // sqrt((SCREEN_WIDTH * SCREEN_HEIGHT) / MAX_PALETTE) == 15.8 (if SCREEN_WIDTH = 320, SCREEN_HEIGHT = 200, MAX_PALETTE = 256)
#define OFFSET              2
#define COLS_PER_ROW        21      // (SCREEN_WIDTH / SQUARE_SIZE) == 21.3333 (if SCREEN_WIDTH = 320, SQUARE_SIZE = 15)
#define MAX_PALETTE         256
#define COLOR_WHITE         15
#define COLOR_RED           41
#define PADDING             1
#define MOUSE_CURSOR_SIZE   3
char textbuffer[17]; // utility buffer for textual stuff
void input(void) {
    if (keystate(KEY_ESCAPE)) exit(0); // exit the game
}    
void update(void) {
}
void draw(void) {
    int palindex = 0;
    int x, y;
    // mouse position & color
    int mx = mousex(), my = mousey();
    int mc = COLOR_RED;
    // draw each color of the palette
    for (int row = 0; palindex < MAX_PALETTE; row++) {
        // row by row, as long as we have colors in the palette to draw
        for (int col = 0; col < COLS_PER_ROW && palindex < MAX_PALETTE; col++) {
            x = OFFSET + (col * SQUARE_SIZE);
            y = OFFSET + (row * SQUARE_SIZE);
            setcolor(palindex);
            bar(x, y, SQUARE_SIZE - PADDING, SQUARE_SIZE - PADDING);
            if (mx > x && mx < (x + SQUARE_SIZE) && my > y && my < (y + SQUARE_SIZE))  {
                setcolor(COLOR_WHITE);
                x = (SCREEN_WIDTH * 0.5) - 50;
                y = SCREEN_HEIGHT - 15;
                sprintf(textbuffer, "getcolor() = %d", palindex); outtextxy(x, y, textbuffer);
                
                // if the mouse (that has a red cursor) is inside a redish color
                // give to it a white color to increase contrast
                if (palindex == 4 || palindex == 12 || (palindex >= 34 && palindex <= 41) || (palindex >= 108 && palindex <= 114))
                    mc = COLOR_WHITE;
            }
            palindex++;
        }
    }
    // mouse cursor
    setcolor(mc);
    bar(mx, my, MOUSE_CURSOR_SIZE, MOUSE_CURSOR_SIZE);
}
int main(int argc, char* argv[]) {
    setvideomode(videomode_320x200);
    setdoublebuffer(1);
    uint8_t* screen = screenbuffer();
    while (!shuttingdown()) {
        waitvbl();
        clearscreen();
        
        input();
        update();
        draw();
        screen = swapbuffers();
    }
    
    return 0;
}