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index.js
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index.js
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'use strict';
module.exports = function() {
var gradients = null;
var minNum = 0;
var maxNum = 100;
var colours = ['ff0000', 'ffff00', '00ff00', '0000ff'];
setColours(colours);
function setColours(spectrum) {
if (spectrum.length < 2) {
throw new Error('Rainbow must have two or more colours.');
} else {
var increment = (maxNum - minNum) / (spectrum.length - 1);
var firstGradient = new ColourGradient();
firstGradient.setGradient(spectrum[0], spectrum[1]);
firstGradient.setNumberRange(minNum, minNum + increment);
gradients = [firstGradient];
for (var i = 1; i < spectrum.length - 1; i++) {
var colourGradient = new ColourGradient();
colourGradient.setGradient(spectrum[i], spectrum[i + 1]);
colourGradient.setNumberRange(minNum + increment * i, minNum + increment * (i + 1));
gradients[i] = colourGradient;
}
colours = spectrum;
return this;
}
}
this.setColors = this.setColours;
this.setSpectrum = function() {
setColours(arguments);
return this;
}
this.setSpectrumByArray = function(array) {
setColours(array);
return this;
}
this.colourAt = function(number) {
if (isNaN(number)) {
throw new TypeError(number + ' is not a number');
} else if (gradients.length === 1) {
return gradients[0].colourAt(number);
} else {
var segment = (maxNum - minNum) / (gradients.length);
var index = Math.min(Math.floor((Math.max(number, minNum) - minNum) / segment), gradients.length - 1);
return gradients[index].colourAt(number);
}
}
this.colorAt = this.colourAt;
this.setNumberRange = function(minNumber, maxNumber) {
if (maxNumber > minNumber) {
minNum = minNumber;
maxNum = maxNumber;
setColours(colours);
} else {
throw new RangeError('maxNumber (' + maxNumber + ') is not greater than minNumber (' + minNumber + ')');
}
return this;
}
}
function ColourGradient() {
var startColour = 'ff0000';
var endColour = '0000ff';
var minNum = 0;
var maxNum = 100;
this.setGradient = function(colourStart, colourEnd) {
startColour = getHexColour(colourStart);
endColour = getHexColour(colourEnd);
}
this.setNumberRange = function(minNumber, maxNumber) {
if (maxNumber > minNumber) {
minNum = minNumber;
maxNum = maxNumber;
} else {
throw new RangeError('maxNumber (' + maxNumber + ') is not greater than minNumber (' + minNumber + ')');
}
}
this.colourAt = function(number) {
return calcHex(number, startColour.substring(0, 2), endColour.substring(0, 2)) + calcHex(number, startColour.substring(2, 4), endColour.substring(2, 4)) + calcHex(number, startColour.substring(4, 6), endColour.substring(4, 6));
}
function calcHex(number, channelStart_Base16, channelEnd_Base16) {
var num = number;
if (num < minNum) {
num = minNum;
}
if (num > maxNum) {
num = maxNum;
}
var numRange = maxNum - minNum;
var cStart_Base10 = parseInt(channelStart_Base16, 16);
var cEnd_Base10 = parseInt(channelEnd_Base16, 16);
var cPerUnit = (cEnd_Base10 - cStart_Base10) / numRange;
var c_Base10 = Math.round(cPerUnit * (num - minNum) + cStart_Base10);
return formatHex(c_Base10.toString(16));
}
function formatHex(hex) {
if (hex.length === 1) {
return '0' + hex;
} else {
return hex;
}
}
function isHexColour(string) {
var regex = /^#?[0-9a-fA-F]{6}$/i;
return regex.test(string);
}
function getHexColour(string) {
if (isHexColour(string)) {
return string.substring(string.length - 6, string.length);
} else {
var colourNames =
[
['red', 'ff0000'],
['lime', '00ff00'],
['blue', '0000ff'],
['yellow', 'ffff00'],
['orange', 'ff8000'],
['aqua', '00ffff'],
['fuchsia', 'ff00ff'],
['white', 'ffffff'],
['black', '000000'],
['gray', '808080'],
['grey', '808080'],
['silver', 'c0c0c0'],
['maroon', '800000'],
['olive', '808000'],
['green', '008000'],
['teal', '008080'],
['navy', '000080'],
['purple', '800080']
];
for (var i = 0; i < colourNames.length; i++) {
if (string.toLowerCase() === colourNames[i][0]) {
return colourNames[i][1];
}
}
throw new Error(string + ' is not a valid colour.');
}
}
};