Simple C++ Animation on Console Windows – Random Squares on CodePage 437

Are you still using Turbo C with graphics (code with initgraphics) ? It has been outdated for at least a decade. It is 16-bit graphics so please DON’T use it ever ever again because it is not useful and on modern OS (win7 or later) it does not support directly the 16-bit DOS applications.

Now, this is another small animation program I made, please download this windows application first (pre-compiled windows PE binary, zipped, 169KB) . The screenshot is as follows:

It is compiled on g++ compiler windows, so at least 32bit but the same source code can also be compiled for 64-bit executables. So it is modern.

It draws randomly rectangles with random colours continuously until you close the application manually (or Ctrl + C to break).

Do you know that all the drawings are not actually based on ‘graphics’, there is no drawline, drawpixel such things. Just simply print to console with colour squares!

So how do we make this possible?

1. SetConsoleOutputCP(437) allows setting code page to 437, where the extended ASCII 219 equals a solid square.

2. Use a modern gotoxy to stay in the same screen without scrolling

3. Print the characters to console and wait for some interval, which makes the animation.

Here is the C++ source code.

/* http://HelloACM.com */
#include <iostream>
#include <stdio.h>
#include <windows.h>
#include <unistd.h> // usleep
#include <time.h> // for time

using namespace std;

const unsigned char BLACK = 219;

/* type of each pixel */
typedef struct {
    unsigned char elem;
    unsigned char color;
} SCREENELEMENT;

BOOL gotoxy(const WORD x, const WORD y) {
    COORD xy;
    xy.X = x;
    xy.Y = y;
    return SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), xy);
}

/* print the screen to console */
inline
void printScreen(int width, int height, SCREENELEMENT **screen) {
    gotoxy(1, 1); // top-left corner
    for (int i = 0; i < height; i ++) {
        for (int j = 0; j < width; j ++) {             
                SCREENELEMENT *cur = &screen[i][j];             
                SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE), cur->color);
                printf("%c", cur->elem); // may be faster than cout
        }
    }
}

/* initialize the screen to element se */
inline
void initScreen(int width, int height, SCREENELEMENT **screen, SCREENELEMENT se) {
    for (int i = 0; i < height; i ++) {
        for (int j = 0; j < width; j ++) {
            screen[i][j] = se;
        }
    }
}

/* draw a rectangle to (x, y), size (szx, szy) */
inline
void putRectangle(int x, int y, int szx, int szy, int color, int height, SCREENELEMENT **screen) {
    for (int i = y; i < y + szy; i ++) {
        for (int j = x; j < x + szx; j ++) {
            screen[i][j].color = color;
        }
    }
}

int main() {
    SetConsoleOutputCP(437);
    CONSOLE_SCREEN_BUFFER_INFO csbi;
    int ret;
    /* get the width of the console */
    ret = GetConsoleScreenBufferInfo(GetStdHandle(STD_OUTPUT_HANDLE), &csbi);
    int width = 80;
    if (ret) {
        width = csbi.dwSize.X;
    }
    int height = csbi.srWindow.Bottom - csbi.srWindow.Top;
    SCREENELEMENT **s = new SCREENELEMENT*[height];
    for (int i = 0; i < height; i ++) {
        s[i] = new SCREENELEMENT[width];
    }
    SCREENELEMENT se;
    se.elem = BLACK;
    se.color = 0;
    initScreen(width, height, s, se);
    se.color = 15;
    srand(time(NULL));
    for (;;) {
        int x = rand() % width;
        int y = rand() % height;
        int szx = rand() % (width - x);
        int szy = rand() % (height - y);
        /* color from 0 to 15 */
        int c = rand() % 15 + 1;
        /* put a random rectangle */
        putRectangle(x, y, szx, szy, c, height, s);
        printScreen(width, height, s);
        usleep(20); // optional interval
    }
    for (int i = 0; i < height; i ++) {
        delete[] s[i];
    }
    delete[] s;
    return 0; /* use Ctrl+C, never returns */
}

By the way, we can possibly change the file extension from *.EXE to *.SCR and make it a screen saver!

–EOF (The Ultimate Computing & Technology Blog) —