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nefd on 08/31/11

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Last Edited at 08/31/11 12:07am

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Bresenham\'s Line Algorithm

/ Published in: JavaScript

Code obtained from a [stackoverflow question](http://stackoverflow.com/questions/4672279/bresenham-algorithm-in-javascript). This is a javascript implementation of the [Bresenham line algorithm](http://en.wikipedia.org/wiki/Bresenham's_line_algorithm). Given two points, this function will return an array of coordinates which go from point A to point B, one step at a time.

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function calcStraightLine (startCoordinates, endCoordinates) {
    var coordinatesArray = new Array();
    // Translate coordinates
    var x1 = startCoordinates.left;
    var y1 = startCoordinates.top;
    var x2 = endCoordinates.left;
    var y2 = endCoordinates.top;
    // Define differences and error check
    var dx = Math.abs(x2 - x1);
    var dy = Math.abs(y2 - y1);
    var sx = (x1 < x2) ? 1 : -1;
    var sy = (y1 < y2) ? 1 : -1;
    var err = dx - dy;
    // Set first coordinates
    coordinatesArray.push(new Coordinates(y1, x1));
    // Main loop
    while (!((x1 == x2) && (y1 == y2))) {
      var e2 = err << 1;
      if (e2 > -dy) {
        err -= dy;
        x1 += sx;
      }
      if (e2 < dx) {
        err += dx;
        y1 += sy;
      }
      // Set coordinates
      coordinatesArray.push(new Coordinates(y1, x1));
    }
    // Return the result
    return coordinatesArray;
  }