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