helper.js

define([
], function() {
    return {
        rainbow: function(numOfSteps, step) {
            // This function generates vibrant, "evenly spaced" colours (i.e. no clustering).
            // This is ideal for creating easily distinguishable vibrant markers in Google Maps and other apps.
            // Adam Cole, 2011-Sept-14
            // HSV to RBG adapted from: http://mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
            var r, g, b;
            var h = step / numOfSteps;
            var i = ~~(h * 6);
            var f = h * 6 - i;
            var q = 1 - f;
            switch (i % 6) {
                case 0: r = 1; g = f; b = 0; break;
                case 1: r = q; g = 1; b = 0; break;
                case 2: r = 0; g = 1; b = f; break;
                case 3: r = 0; g = q; b = 1; break;
                case 4: r = f; g = 0; b = 1; break;
                case 5: r = 1; g = 0; b = q; break;
            }
            var c = "#" +
                ("00" + (~ ~(r * 255)).toString(16)).slice(-2) +
                ("00" + (~ ~(g * 255)).toString(16)).slice(-2) +
                ("00" + (~ ~(b * 255)).toString(16)).slice(-2);
            return c;
        },
        getRandomInt: function(min, max) {
            // Includes min and max
            return Math.floor(Math.random() * (max - min + 1)) + min;
        },
        checkLineCollision: function(line1StartX, line1StartY, line1EndX, line1EndY, line2StartX, line2StartY, line2EndX, line2EndY) {
            // if the lines intersect, the result contains the x and y of the intersection
            // (treating the lines as infinite) and booleans for whether line segment 1 or
            // line segment 2 contain the point
            var denominator, a, b, numerator1, numerator2, result = {
                x: null,
                y: null,
                onLine1: false,
                onLine2: false
            };
            denominator = ((line2EndY - line2StartY) * (line1EndX - line1StartX)) - ((line2EndX - line2StartX) * (line1EndY - line1StartY));
            if (denominator == 0) {
                return result;
            }
            a = line1StartY - line2StartY;
            b = line1StartX - line2StartX;
            numerator1 = ((line2EndX - line2StartX) * a) - ((line2EndY - line2StartY) * b);
            numerator2 = ((line1EndX - line1StartX) * a) - ((line1EndY - line1StartY) * b);
            a = numerator1 / denominator;
            b = numerator2 / denominator;

            // if we cast these lines infinitely in both directions, they intersect here:
            result.x = line1StartX + (a * (line1EndX - line1StartX));
            result.y = line1StartY + (a * (line1EndY - line1StartY));
            
            // if line1 is a segment and line2 is infinite, they intersect if:
            if (a > 0 && a < 1) {
                result.onLine1 = true;
            }
            // if line2 is a segment and line1 is infinite, they intersect if:
            if (b > 0 && b < 1) {
                result.onLine2 = true;
            }
            // if line1 and line2 are segments, they intersect if both of the above are true
            return result;
        }
    }
})