Elegant solution for coloring chess tiles

Question

I am re-developing a chess game I wrote in Java, and was wondering if there is an elegant algorithm to color chess tiles on a numbered chess board.

Right now my solution uses if else statements to determine if the tile is on an even or odd row, and based on that, if it should be a light or dark square.

Answer 1

The most elegant way I can think of, given that you have the row and column indices, is the following:

bool isLight = (row % 2) == (column % 2);

or, conversely:

bool isDark = (row % 2) != (column % 2);

Basically, a tile on a chessboard is light wherever both the column and row are mutually odd or even, and is dark otherwise.

Answer 2

bool isLight = ((row ^ column) & 1) == 0;

XOR together the row and column indices and look at the least-significant bit. Changing the row or column index by one will invert the result, hence it generates a checker pattern.

Answer 3

Another suggestion, very straightforward:

isLight = (row + column) % 2 == 0;

Adding the row and column gives the number of horizontal and vertical steps away from the top-left tile.

Even number of steps gives light colour.
Odd numbers of steps gives dark colour.

Answer 4

This one assumes that our squares are numbered in the range [0..63].

bool IsLight(int i)
{
    return 0!=(i>>3^i)&1;
}

Figuring out why it works is half the fun. :)

Answer 5

1. Number the tiles. You could derive this information by calculating row*8+column or something similar.

2. Take modulus 16 of the grid number. (There are 16 positions before the tiles repeat.)

3. Color the tile based on if it has an even or an odd number. Flip the tile color if the result is greater than 7.

Code for zero-based indices:

int cellNum = (row*8+column) % 16;
bool isSecondRow = cellNum > 7;
if(cellNum % 2 == 0 ^ isSecondRow){ //XOR operator
    setColor(Color.White);
}else{
    setColor(Color.Charcoal);
}

Answer 6

Although this approach isn't really necessary for something as simple as a chess board, when I think of an elegant way to render something related to the view, I want to make it as easy as possible to change the rendered view as possible. For example, suppose you decided you wanted to alternate black and white on each row, but not each column. The one-liners used in answers so far would have to be re-written.

If I was to go as far as I could with this and make it as easy to redesign the pattern on the Chess board as possible, here is what I would do:

1) I would make a file that indicates what color each square in the chess board is.

For example, I could make a file chess_board_pattern.config that looks something like this:

bwbwbwbw
wbwbwbwb
bwbwbwbw
wbwbwbwb
bwbwbwbw
wbwbwbwb
bwbwbwbw
wbwbwbwb

2) I would write a class/component/whatever that can read this file and create some kind of object that represents the board pattern:

public class BoardPattern {
    private Color[][] pattern;

    public BoardPattern(File patternFile)
    {
        pattern = new Color[8][8];
        //Parse the file and fill in the values of pattern
    }

    public Color[][] getPattern {
        return pattern;
    }
}

3) I would then use that class in the function that actually draws the board.

File patternFile = new File("chess_board_pattern.ini");
Color[][] pattern = new BoardPattern(patternFile).getPattern();
ChessBoardDrawable chessBoard = new ChessBoardDrawable();

for(int row = 0; row < 8; row++) {
    for(int column; column < 8; column++) {
        chessBoard.drawSquare(row, column, Color[row][column]);
    }
}

Again, this is a lot harder than is necessary for a Chess board. I think in general, though, when working on more complicated projects, it's best to come up with generalized solutions like this instead of writing code that's difficult to change later.