stringUtils.js

var stringUtils = (function() {
    var chars = ['@','#','H','$',
                 'A','*','x','z',
                 'o','+','=','-', 
                 ':',',','.',' ']

    var getString = function(data, width, height) {
        var next = 0
        var string = ''

        // data[0] = red
        // data[1] = green
        // data[2] = blue
        // data[3] = alpha

        for (var row = 0; row < height; row++) {
            if (row % 5 != 0) {
                next += 4 * width
                continue
            }

            var line = ''

            for (var col = 0; col < width; col++) {
                if (col % 2 == 0) {
                    var color = data[next] + data[next + 1] + data[next + 2]
                    color = color / 3
                    line = chars[parseInt(color / 16)] + line
                }
                next = next + 4
            }
            string = string + line + '\n'
        }
        return string
    }

    var calculateChangePercentageInUpperRightCorner = function(prevString, newString) {
        var changedCharacters = 0

        var rows = getStringThatShowsMovement(prevString, newString).split('\n')
        for (var row=0; row < rows.length/4; ++row) {
            var lastQuarter = rows[row].substring(rows[row].length - (rows[row].length/4))
            changedCharacters += lastQuarter.split(' ').join('').length
        }

        var totalCharactersInUpperRightCorner = (rows.length/4) * (rows[0].length/4)
        return changedCharacters / totalCharactersInUpperRightCorner
    }

    var getStringThatShowsMovement = function(prevString, newString) {
        var string = ''
        for (var i=0; i < newString.length; i++) {
            if (newString.charAt(i) == '\n') {
                string = string + '\n'
            } else if (Math.abs(getIndex(newString.charAt(i)) - getIndex(prevString.charAt(i))) < 4) { // I like four.
                string = string + ' '
            } else {
                string = string + '@'
            }
        }
        return string
    }

    var getIndex = function(char) {
        for (var i = 0; i < chars.length; ++i) {
            if (chars[i] == char) { return i }
        }
        return 100
    }

    return {
        getString: getString,
        calculateChangePercentageInUpperRightCorner: calculateChangePercentageInUpperRightCorner
    }
})()