Modularise JS source in 'lib' subdirectory.

Generate public API documention via jsdoc comments.

lib/colour.js

@@ -0,0 +1,104 @@
+'use strict';
+
+const color = require('color');
+const is = require('./is');
+
+/**
+ * Colourspaces.
+ * @private
+ */
+const colourspace = {
+  multiband: 'multiband',
+  'b-w': 'b-w',
+  bw: 'b-w',
+  cmyk: 'cmyk',
+  srgb: 'srgb'
+};
+
+/**
+ * Set the background for the `embed`, `flatten` and `extend` operations.
+ * The default background is `{r: 0, g: 0, b: 0, a: 1}`, black without transparency.
+ *
+ * Delegates to the _color_ module, which can throw an Error
+ * but is liberal in what it accepts, clipping values to sensible min/max.
+ * The alpha value is a float between `0` (transparent) and `1` (opaque).
+ *
+ * @param {String|Object} rgba - parsed by the [color](https://www.npmjs.org/package/color) module to extract values for red, green, blue and alpha.
+ * @returns {Sharp}
+ * @throws {Error} Invalid parameter
+ */
+const background = function background (rgba) {
+  const colour = color(rgba);
+  this.options.background = colour.rgbArray();
+  this.options.background.push(colour.alpha() * 255);
+  return this;
+};
+
+/**
+ * Convert to 8-bit greyscale; 256 shades of grey.
+ * This is a linear operation. If the input image is in a non-linear colour space such as sRGB, use `gamma()` with `greyscale()` for the best results.
+ * By default the output image will be web-friendly sRGB and contain three (identical) color channels.
+ * This may be overridden by other sharp operations such as `toColourspace('b-w')`,
+ * which will produce an output image containing one color channel.
+ * An alpha channel may be present, and will be unchanged by the operation.
+ * @param {Boolean} [greyscale=true]
+ * @returns {Sharp}
+ */
+const greyscale = function greyscale (greyscale) {
+  this.options.greyscale = is.bool(greyscale) ? greyscale : true;
+  return this;
+};
+
+/**
+ * Alternative spelling of `greyscale`.
+ * @param {Boolean} [grayscale=true]
+ * @returns {Sharp}
+ */
+const grayscale = function grayscale (grayscale) {
+  return this.greyscale(grayscale);
+};
+
+/**
+ * Set the output colourspace.
+ * By default output image will be web-friendly sRGB, with additional channels interpreted as alpha channels.
+ * @param {String} [colourspace] - output colourspace e.g. `srgb`, `rgb`, `cmyk`, `lab`, `b-w` [...](https://github.com/jcupitt/libvips/blob/master/libvips/iofuncs/enumtypes.c#L568)
+ * @returns {Sharp}
+ * @throws {Error} Invalid parameters
+ */
+const toColourspace = function toColourspace (colourspace) {
+  if (!is.string(colourspace)) {
+    throw new Error('Invalid output colourspace ' + colourspace);
+  }
+  this.options.colourspace = colourspace;
+  return this;
+};
+
+/**
+ * Alternative spelling of `toColourspace`.
+ * @param {String} [colorspace] - output colorspace.
+ * @returns {Sharp}
+ * @throws {Error} Invalid parameters
+ */
+const toColorspace = function toColorspace (colorspace) {
+  return this.toColourspace(colorspace);
+};
+
+/**
+ * Decorate the Sharp prototype with colour-related functions.
+ * @private
+ */
+module.exports = function (Sharp) {
+  // Public instance functions
+  [
+    background,
+    greyscale,
+    grayscale,
+    toColourspace,
+    toColorspace
+  ].forEach(function (f) {
+    Sharp.prototype[f.name] = f;
+  });
+  // Class attributes
+  Sharp.colourspace = colourspace;
+  Sharp.colorspace = colourspace;
+};