148 lines
4.4 KiB
JavaScript
148 lines
4.4 KiB
JavaScript
'use strict';
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const is = require('./is');
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/**
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* Boolean operations for bandbool.
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* @private
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*/
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const bool = {
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and: 'and',
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or: 'or',
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eor: 'eor'
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};
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/**
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* Remove alpha channel, if any. This is a no-op if the image does not have an alpha channel.
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*
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* @example
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* sharp('rgba.png')
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* .removeAlpha()
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* .toFile('rgb.png', function(err, info) {
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* // rgb.png is a 3 channel image without an alpha channel
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* });
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*
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* @returns {Sharp}
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*/
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function removeAlpha () {
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this.options.removeAlpha = true;
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return this;
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}
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/**
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* Ensure alpha channel, if missing. The added alpha channel will be fully opaque. This is a no-op if the image already has an alpha channel.
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*
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* @since 0.21.2
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*
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* @example
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* sharp('rgb.jpg')
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* .ensureAlpha()
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* .toFile('rgba.png', function(err, info) {
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* // rgba.png is a 4 channel image with a fully opaque alpha channel
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* });
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*
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* @returns {Sharp}
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*/
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function ensureAlpha () {
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this.options.ensureAlpha = true;
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return this;
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}
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/**
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* Extract a single channel from a multi-channel image.
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*
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* @example
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* sharp(input)
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* .extractChannel('green')
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* .toColourspace('b-w')
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* .toFile('green.jpg', function(err, info) {
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* // info.channels === 1
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* // green.jpg is a greyscale image containing the green channel of the input
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* });
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*
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* @param {number|string} channel - zero-indexed channel/band number to extract, or `red`, `green`, `blue` or `alpha`.
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* @returns {Sharp}
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* @throws {Error} Invalid channel
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*/
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function extractChannel (channel) {
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const channelMap = { red: 0, green: 1, blue: 2, alpha: 3 };
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if (Object.keys(channelMap).includes(channel)) {
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channel = channelMap[channel];
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}
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if (is.integer(channel) && is.inRange(channel, 0, 4)) {
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this.options.extractChannel = channel;
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} else {
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throw is.invalidParameterError('channel', 'integer or one of: red, green, blue, alpha', channel);
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}
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return this;
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}
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/**
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* Join one or more channels to the image.
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* The meaning of the added channels depends on the output colourspace, set with `toColourspace()`.
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* By default the output image will be web-friendly sRGB, with additional channels interpreted as alpha channels.
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* Channel ordering follows vips convention:
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* - sRGB: 0: Red, 1: Green, 2: Blue, 3: Alpha.
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* - CMYK: 0: Magenta, 1: Cyan, 2: Yellow, 3: Black, 4: Alpha.
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*
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* Buffers may be any of the image formats supported by sharp: JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data.
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* For raw pixel input, the `options` object should contain a `raw` attribute, which follows the format of the attribute of the same name in the `sharp()` constructor.
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*
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* @param {Array<string|Buffer>|string|Buffer} images - one or more images (file paths, Buffers).
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* @param {Object} options - image options, see `sharp()` constructor.
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* @returns {Sharp}
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* @throws {Error} Invalid parameters
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*/
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function joinChannel (images, options) {
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if (Array.isArray(images)) {
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images.forEach(function (image) {
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this.options.joinChannelIn.push(this._createInputDescriptor(image, options));
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}, this);
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} else {
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this.options.joinChannelIn.push(this._createInputDescriptor(images, options));
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}
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return this;
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}
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/**
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* Perform a bitwise boolean operation on all input image channels (bands) to produce a single channel output image.
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*
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* @example
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* sharp('3-channel-rgb-input.png')
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* .bandbool(sharp.bool.and)
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* .toFile('1-channel-output.png', function (err, info) {
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* // The output will be a single channel image where each pixel `P = R & G & B`.
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* // If `I(1,1) = [247, 170, 14] = [0b11110111, 0b10101010, 0b00001111]`
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* // then `O(1,1) = 0b11110111 & 0b10101010 & 0b00001111 = 0b00000010 = 2`.
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* });
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*
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* @param {string} boolOp - one of `and`, `or` or `eor` to perform that bitwise operation, like the C logic operators `&`, `|` and `^` respectively.
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* @returns {Sharp}
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* @throws {Error} Invalid parameters
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*/
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function bandbool (boolOp) {
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if (is.string(boolOp) && is.inArray(boolOp, ['and', 'or', 'eor'])) {
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this.options.bandBoolOp = boolOp;
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} else {
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throw is.invalidParameterError('boolOp', 'one of: and, or, eor', boolOp);
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}
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return this;
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}
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/**
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* Decorate the Sharp prototype with channel-related functions.
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* @private
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*/
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module.exports = function (Sharp) {
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Object.assign(Sharp.prototype, {
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// Public instance functions
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removeAlpha,
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ensureAlpha,
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extractChannel,
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joinChannel,
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bandbool
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});
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// Class attributes
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Sharp.bool = bool;
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};
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