map

int [][] map = { // 20 x 20
    { -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1},
    {154, 155, 156,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1},
    {163, 164, 165, 166,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1},
    { -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1, 153, 154, 155, 156,  -1,  -1,  -1, 153, 154, 155, 156,  -1},
    { -1,  -1, 153, 154, 155, 156,  -1,  -1, 162, 163, 164, 165, 166,  -1,  -1, 162, 163, 164, 165, 166},
    { -1,  -1, 162, 163, 164, 165, 166,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1},
    { -1,   8,  -1,  -1,  -1,   8,  -1,  -1,  -1,  -1,  -1, 153, 154, 155, 156,  -1,  -1,  -1,   8,  -1},
    { -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1, 162, 163, 164, 165, 166,  -1,  -1,  -1,  -1},
    { -1,  -1, 135,  -1,  -1,  -1, 135,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1},
    {101,  65,  65,  37,  38,  39,  40,  41,  42,  46,  46,  -1,  -1,  -1,  -1, 136,  -1,  -1,  33,  -1},
    {110,  -1,  -1,  -1,  47,  48,  49,  50,  -1,  55,  55,  -1,  46,  37,  38,  39,  40,  41,  42, 101},
    {110,  -1,  -1,  -1,  56,  57,  58,  59,  -1,  64,  55,  46,  55,  -1,  47,  48,  49,  50,  -1, 110},
    {110,  72,  73,  -1,  -1,  66,  67,  78,  79,  -1,  64,  55,  64,  -1,  56,  57,  58,  59,  -1, 101},
    {110,  81,  82,  83,  84,  85,  86,  87,  -1,  -1,  -1,  64,  -1,  -1,  -1,  66,  67,  -1,  -1, 110},
    {110,  -1,  91,  92,  93,  94,  95,  96,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1, 101},
    {110,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1, 101},
    {110,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1, 101},
    {110, 121, 122, 123,  -1,  -1,  -1,  -1,  -1, 121, 122, 123,  -1,  -1,  -1,  -1, 121, 122, 123, 101},
    {110, 130, 131, 132,  -1,  -1,  -1,  -1,  -1, 130, 131, 132,  -1,  -1,  -1,  -1, 130, 131, 132, 101},
    {110, 139, 140, 141, 144, 146,  -1,  -1,  -1, 139, 140, 141,  -1,  -1,  -1, 146, 139, 140, 141, 110}
};

PImage
    tiles,
    tile; // ismanusvaikas.lt/data/tileset2.png - 288 x 608

int
    mapSize = 20,
    tileSize = 32,
    tilesWidth = 9, // columns
    tilesHeight = 19, // rows // actually not used
    tilesX = tileSize * (mapSize + 2),
    chosen = -1;

boolean showTile = false;

void setup () {
    size(31 * 32, 20 * 32);
    noFill();
    stroke(255, 50);
    textSize(tileSize);
    tiles = loadImage("data/tileset2.png"); // 9 x 19
}

void grid () { // gal ir galima daryti su linijomis, bet tinka ir taip (nežinau, kas paprasčiau)
    for (int y = 0; y < mapSize; ++y) {
        for (int x = 0; x < mapSize; ++x)
            square(x * tileSize, y * tileSize, tileSize);
    }
}

void _map () {
    for (int y = 0; y < mapSize; ++y) {
        for (int x = 0; x < mapSize; ++x){
            int temp = map[y][x]; // atrodo pakankamai keistai, tačiau taip ir yra –
            // aš pirmiausia susirandu didelę ląstelę, ir tuomet joje ieškau konkrečios
            if (!(temp == -1)){
                tile = tiles.get(temp % tilesWidth * tileSize, temp / tilesWidth * tileSize, tileSize, tileSize);
                image(tile, x * tileSize, y * tileSize);
            }
        }
    }
}

void keyPressed () {
    if (key == TAB)
        showTile = !showTile;
}

void paint () {
    if (mouseX > tilesX && mouseX < tilesX + tiles.width && mousePressed) {
        chosen = ((mouseX - tilesX) / tileSize) + (mouseY / tileSize * tilesWidth);
        showTile = true;
    }

    if (showTile) {
        tile = tiles.get(chosen % tilesWidth * tileSize, chosen / tilesWidth * tileSize, tileSize, tileSize);
        image(tile, mouseX - tileSize/2, mouseY - tileSize/2);
    }

    if (mouseX > 0 && mouseX < mapSize * tileSize && mouseY > 0 && mouseY < height && mousePressed)
            map[mouseY/tileSize][mouseX/tileSize] = chosen;
}

void draw () {
    background(85, 180, 250);
    image(tiles, tilesX, 0, tiles.width, tiles.height); // available tiles
    grid();
    _map();
    paint();
    text(chosen, width * 0.95, height * 0.95);
}