Current File : //proc/309157/root/www/specpages-backup/node_modules/sharp/lib/channel.js
'use strict';
const is = require('./is');
/**
* Boolean operations for bandbool.
* @private
*/
const bool = {
and: 'and',
or: 'or',
eor: 'eor'
};
/**
* Remove alpha channel, if any. This is a no-op if the image does not have an alpha channel.
*
* @example
* sharp('rgba.png')
* .removeAlpha()
* .toFile('rgb.png', function(err, info) {
* // rgb.png is a 3 channel image without an alpha channel
* });
*
* @returns {Sharp}
*/
function removeAlpha () {
this.options.removeAlpha = true;
return this;
}
/**
* 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.
*
* @example
* sharp('rgb.jpg')
* .ensureAlpha()
* .toFile('rgba.png', function(err, info) {
* // rgba.png is a 4 channel image with a fully opaque alpha channel
* });
*
* @returns {Sharp}
*/
function ensureAlpha () {
this.options.ensureAlpha = true;
return this;
}
/**
* Extract a single channel from a multi-channel image.
*
* @example
* sharp(input)
* .extractChannel('green')
* .toFile('input_green.jpg', function(err, info) {
* // info.channels === 1
* // input_green.jpg contains the green channel of the input image
* });
*
* @param {Number|String} channel - zero-indexed band number to extract, or `red`, `green` or `blue` as alternative to `0`, `1` or `2` respectively.
* @returns {Sharp}
* @throws {Error} Invalid channel
*/
function extractChannel (channel) {
if (channel === 'red') {
channel = 0;
} else if (channel === 'green') {
channel = 1;
} else if (channel === 'blue') {
channel = 2;
}
if (is.integer(channel) && is.inRange(channel, 0, 4)) {
this.options.extractChannel = channel;
} else {
throw is.invalidParameterError('channel', 'integer or one of: red, green, blue', channel);
}
return this;
}
/**
* Join one or more channels to the image.
* The meaning of the added channels depends on the output colourspace, set with `toColourspace()`.
* By default the output image will be web-friendly sRGB, with additional channels interpreted as alpha channels.
* Channel ordering follows vips convention:
* - sRGB: 0: Red, 1: Green, 2: Blue, 3: Alpha.
* - CMYK: 0: Magenta, 1: Cyan, 2: Yellow, 3: Black, 4: Alpha.
*
* Buffers may be any of the image formats supported by sharp: JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data.
* 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.
*
* @param {Array<String|Buffer>|String|Buffer} images - one or more images (file paths, Buffers).
* @param {Object} options - image options, see `sharp()` constructor.
* @returns {Sharp}
* @throws {Error} Invalid parameters
*/
function joinChannel (images, options) {
if (Array.isArray(images)) {
images.forEach(function (image) {
this.options.joinChannelIn.push(this._createInputDescriptor(image, options));
}, this);
} else {
this.options.joinChannelIn.push(this._createInputDescriptor(images, options));
}
return this;
}
/**
* Perform a bitwise boolean operation on all input image channels (bands) to produce a single channel output image.
*
* @example
* sharp('3-channel-rgb-input.png')
* .bandbool(sharp.bool.and)
* .toFile('1-channel-output.png', function (err, info) {
* // The output will be a single channel image where each pixel `P = R & G & B`.
* // If `I(1,1) = [247, 170, 14] = [0b11110111, 0b10101010, 0b00001111]`
* // then `O(1,1) = 0b11110111 & 0b10101010 & 0b00001111 = 0b00000010 = 2`.
* });
*
* @param {String} boolOp - one of `and`, `or` or `eor` to perform that bitwise operation, like the C logic operators `&`, `|` and `^` respectively.
* @returns {Sharp}
* @throws {Error} Invalid parameters
*/
function bandbool (boolOp) {
if (is.string(boolOp) && is.inArray(boolOp, ['and', 'or', 'eor'])) {
this.options.bandBoolOp = boolOp;
} else {
throw is.invalidParameterError('boolOp', 'one of: and, or, eor', boolOp);
}
return this;
}
/**
* Decorate the Sharp prototype with channel-related functions.
* @private
*/
module.exports = function (Sharp) {
Object.assign(Sharp.prototype, {
// Public instance functions
removeAlpha,
ensureAlpha,
extractChannel,
joinChannel,
bandbool
});
// Class attributes
Sharp.bool = bool;
};
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