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Expand linear operation to allow use of per-channel arrays #3303

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Anton Marsden
2022-07-23 21:33:44 +12:00
committed by Lovell Fuller
parent b9261c243c
commit 74e3f73934
10 changed files with 104 additions and 34 deletions
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43
lib/operation.js
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@@ -644,26 +644,55 @@ function boolean (operand, operator, options) {
}
/**
* Apply the linear formula a * input + b to the image (levels adjustment)
* @param {number} [a=1.0] multiplier
* @param {number} [b=0.0] offset
* Apply the linear formula `a` * input + `b` to the image to adjust image levels.
*
* When a single number is provided, it will be used for all image channels.
* When an array of numbers is provided, the array length must match the number of channels.
*
* @example
* await sharp(input)
* .linear(0.5, 2)
* .toBuffer();
*
* @example
* await sharp(rgbInput)
* .linear(
* [0.25, 0.5, 0.75],
* [150, 100, 50]
* )
* .toBuffer();
*
* @param {(number|number[])} [a=[]] multiplier
* @param {(number|number[])} [b=[]] offset
* @returns {Sharp}
* @throws {Error} Invalid parameters
*/
function linear (a, b) {
if (!is.defined(a) && is.number(b)) {
a = 1.0;
} else if (is.number(a) && !is.defined(b)) {
b = 0.0;
}
if (!is.defined(a)) {
this.options.linearA = 1.0;
this.options.linearA = [];
} else if (is.number(a)) {
this.options.linearA = [a];
} else if (Array.isArray(a) && a.length && a.every(is.number)) {
this.options.linearA = a;
} else {
throw is.invalidParameterError('a', 'numeric', a);
throw is.invalidParameterError('a', 'number or array of numbers', a);
}
if (!is.defined(b)) {
this.options.linearB = 0.0;
this.options.linearB = [];
} else if (is.number(b)) {
this.options.linearB = [b];
} else if (Array.isArray(b) && b.length && b.every(is.number)) {
this.options.linearB = b;
} else {
throw is.invalidParameterError('b', 'numeric', b);
throw is.invalidParameterError('b', 'number or array of numbers', b);
}
if (this.options.linearA.length !== this.options.linearB.length) {
throw new Error('Expected a and b to be arrays of the same length');
}
return this;
}