repo_description: High performance Node.js image processing, the fastest module to resize JPEG, PNG, WebP, AVIF and TIFF images. Uses the libvips library.
repo_topics: avif crop exif icc image image-processing javascript jpeg libvips nodejs performance png resize sharp svg tiff webp
code: /*!
    Copyright 2013 Lovell Fuller and others.
    SPDX-License-Identifier: Apache-2.0
  */
  
  const is = require('./is');
  
  /**
   * How accurate an operation should be.
   * @member
   * @private
   */
  const vipsPrecision = {
    integer: 'integer',
    float: 'float',
    approximate: 'approximate'
  };
  
  /**
   * Rotate the output image.
   *
   * The provided angle is converted to a valid positive degree rotation.
   * For example, `-450` will produce a 270 degree rotation.
   *
   * When rotating by an angle other than a multiple of 90,
   * the background colour can be provided with the `background` option.
   *
   * For backwards compatibility, if no angle is provided, `.autoOrient()` will be called.
   *
   * Only one rotation can occur per pipeline (aside from an initial call without
   * arguments to orient via EXIF data). Previous calls to `rotate` in the same
   * pipeline will be ignored.
   *
   * Multi-page images can only be rotated by 180 degrees.
   *
   * Method order is important when rotating, resizing and/or extracting regions,
   * for example `.rotate(x).extract(y)` will produce a different result to `.extract(y).rotate(x)`.
   *
   * @example
   * const rotateThenResize = await sharp(input)
   *   .rotate(90)
   *   .resize({ width: 16, height: 8, fit: 'fill' })
   *   .toBuffer();
   * const resizeThenRotate = await sharp(input)
   *   .resize({ width: 16, height: 8, fit: 'fill' })
   *   .rotate(90)
   *   .toBuffer();
   *
   * @param {number} [angle=auto] angle of rotation.
   * @param {Object} [options] - if present, is an Object with optional attributes.
   * @param {string|Object} [options.background="#000000"] 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 parameters
   */
  function rotate (angle, options) {
    if (!is.defined(angle)) {
      return this.autoOrient();
    }
    if (this.options.angle || this.options.rotationAngle) {
      this.options.debuglog('ignoring previous rotate options');
      this.options.angle = 0;
      this.options.rotationAngle = 0;
    }
    if (is.integer(angle) && !(angle % 90)) {
      this.options.angle = angle;
    } else if (is.number(angle)) {
      this.options.rotationAngle = angle;
      if (is.object(options) && options.background) {
        this._setBackgroundColourOption('rotationBackground', options.background);
      }
    } else {
      throw is.invalidParameterError('angle', 'numeric', angle);
    }
    return this;
  }
  
  /**
   * Auto-orient based on the EXIF `Orientation` tag, then remove the tag.
   * Mirroring is supported and may infer the use of a flip operation.
   *
   * Previous or subsequent use of `rotate(angle)` and either `flip()` or `flop()`
   * will logically occur after auto-orientation, regardless of call order.
   *
   * @example
   * const output = await sharp(input).autoOrient().toBuffer();
   *
   * @example
   * const pipeline = sharp()
   *   .autoOrient()
   *   .resize(null, 200)
   *   .toBuffer(function (err, outputBuffer, info) {
   *     // outputBuffer contains 200px high JPEG image data,
   *     // auto-oriented using EXIF Orientation tag
   *     // info.width and info.height contain the dimensions of the resized image
   *   });
   * readableStream.pipe(pipeline);
   *
   * @returns {Sharp}
   */
  function autoOrient () {
    this.options.input.autoOrient = true;
    return this;
  }
  
  /**
   * Mirror the image vertically (up-down) about the x-axis.
   * This always occurs before rotation, if any.
   *
   * This operation does not work correctly with multi-page images.
   *
   * @example
   * const output = await sharp(input).flip().toBuffer();
   *
   * @param {Boolean} [flip=true]
   * @returns {Sharp}
   */
  function flip (flip) {
    this.options.flip = is.bool(flip) ? flip : true;
    return this;
  }
  
  /**
   * Mirror the image horizontally (left-right) about the y-axis.
   * This always occurs before rotation, if any.
   *
   * @example
   * const output = await sharp(input).flop().toBuffer();
   *
   * @param {Boolean} [flop=true]
   * @returns {Sharp}
   */
  function flop (flop) {
    this.options.flop = is.bool(flop) ? flop : true;
    return this;
  }
  
  /**
   * Perform an affine transform on an image. This operation will always occur after resizing, extraction and rotation, if any.
   *
   * You must provide an array of length 4 or a 2x2 affine transformation matrix.
   * By default, new pixels are filled with a black background. You can provide a background colour with the `background` option.
   * A particular interpolator may also be specified. Set the `interpolator` option to an attribute of the `sharp.interpolators` Object e.g. `sharp.interpolators.nohalo`.
   *
   * In the case of a 2x2 matrix, the transform is:
   * - X = `matrix[0, 0]` \* (x + `idx`) + `matrix[0, 1]` \* (y + `idy`) + `odx`
   * - Y = `matrix[1, 0]` \* (x + `idx`) + `matrix[1, 1]` \* (y + `idy`) + `ody`
   *
   * where:
   * - x and y are the coordinates in input image.
   * - X and Y are the coordinates in output image.
   * - (0,0) is the upper left corner.
   *
   * @since 0.27.0
   *
   * @example
   * const pipeline = sharp()
   *   .affine([[1, 0.3], [0.1, 0.7]], {
   *      background: 'white',
   *      interpolator: sharp.interpolators.nohalo
   *   })
   *   .toBuffer((err, outputBuffer, info) => {
   *      // outputBuffer contains the transformed image
   *      // info.width and info.height contain the new dimensions
   *   });
   *
   * inputStream
   *   .pipe(pipeline);
   *
   * @param {Array<Array<number>>|Array<number>} matrix - affine transformation matrix
   * @param {Object} [options] - if present, is an Object with optional attributes.
   * @param {String|Object} [options.background="#000000"] - parsed by the [color](https://www.npmjs.org/package/color) module to extract values for red, green, blue and alpha.
   * @param {Number} [options.idx=0] - input horizontal offset
   * @param {Number} [options.idy=0] - input vertical offset
   * @param {Number} [options.odx=0] - output horizontal offset
   * @param {Number} [options.ody=0] - output vertical offset
   * @param {String} [options.interpolator=sharp.interpolators.bicubic] - interpolator
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function affine (matrix, options) {
    const flatMatrix = [].concat(...matrix);
    if (flatMatrix.length === 4 && flatMatrix.every(is.number)) {
      this.options.affineMatrix = flatMatrix;
    } else {
      throw is.invalidParameterError('matrix', '1x4 or 2x2 array', matrix);
    }
  
    if (is.defined(options)) {
      if (is.object(options)) {
        this._setBackgroundColourOption('affineBackground', options.background);
        if (is.defined(options.idx)) {
          if (is.number(options.idx)) {
            this.options.affineIdx = options.idx;
          } else {
            throw is.invalidParameterError('options.idx', 'number', options.idx);
          }
        }
        if (is.defined(options.idy)) {
          if (is.number(options.idy)) {
            this.options.affineIdy = options.idy;
          } else {
            throw is.invalidParameterError('options.idy', 'number', options.idy);
          }
        }
        if (is.defined(options.odx)) {
          if (is.number(options.odx)) {
            this.options.affineOdx = options.odx;
          } else {
            throw is.invalidParameterError('options.odx', 'number', options.odx);
          }
        }
        if (is.defined(options.ody)) {
          if (is.number(options.ody)) {
            this.options.affineOdy = options.ody;
          } else {
            throw is.invalidParameterError('options.ody', 'number', options.ody);
          }
        }
        if (is.defined(options.interpolator)) {
          if (is.inArray(options.interpolator, Object.values(this.constructor.interpolators))) {
            this.options.affineInterpolator = options.interpolator;
          } else {
            throw is.invalidParameterError('options.interpolator', 'valid interpolator name', options.interpolator);
          }
        }
      } else {
        throw is.invalidParameterError('options', 'object', options);
      }
    }
  
    return this;
  }
  
  /**
   * Sharpen the image.
   *
   * When used without parameters, performs a fast, mild sharpen of the output image.
   *
   * When a `sigma` is provided, performs a slower, more accurate sharpen of the L channel in the LAB colour space.
   * Fine-grained control over the level of sharpening in "flat" (m1) and "jagged" (m2) areas is available.
   *
   * See {@link https://www.libvips.org/API/current/method.Image.sharpen.html libvips sharpen} operation.
   *
   * @example
   * const data = await sharp(input).sharpen().toBuffer();
   *
   * @example
   * const data = await sharp(input).sharpen({ sigma: 2 }).toBuffer();
   *
   * @example
   * const data = await sharp(input)
   *   .sharpen({
   *     sigma: 2,
   *     m1: 0,
   *     m2: 3,
   *     x1: 3,
   *     y2: 15,
   *     y3: 15,
   *   })
   *   .toBuffer();
   *
   * @param {Object|number} [options] - if present, is an Object with attributes
   * @param {number} [options.sigma] - the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`, between 0.000001 and 10
   * @param {number} [options.m1=1.0] - the level of sharpening to apply to "flat" areas, between 0 and 1000000
   * @param {number} [options.m2=2.0] - the level of sharpening to apply to "jagged" areas, between 0 and 1000000
   * @param {number} [options.x1=2.0] - threshold between "flat" and "jagged", between 0 and 1000000
   * @param {number} [options.y2=10.0] - maximum amount of brightening, between 0 and 1000000
   * @param {number} [options.y3=20.0] - maximum amount of darkening, between 0 and 1000000
   * @param {number} [flat] - (deprecated) see `options.m1`.
   * @param {number} [jagged] - (deprecated) see `options.m2`.
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function sharpen (options, flat, jagged) {
    if (!is.defined(options)) {
      // No arguments: default to mild sharpen
      this.options.sharpenSigma = -1;
    } else if (is.bool(options)) {
      // Deprecated boolean argument: apply mild sharpen?
      this.options.sharpenSigma = options ? -1 : 0;
    } else if (is.number(options) && is.inRange(options, 0.01, 10000)) {
      // Deprecated numeric argument: specific sigma
      this.options.sharpenSigma = options;
      // Deprecated control over flat areas
      if (is.defined(flat)) {
        if (is.number(flat) && is.inRange(flat, 0, 10000)) {
          this.options.sharpenM1 = flat;
        } else {
          throw is.invalidParameterError('flat', 'number between 0 and 10000', flat);
        }
      }
      // Deprecated control over jagged areas
      if (is.defined(jagged)) {
        if (is.number(jagged) && is.inRange(jagged, 0, 10000)) {
          this.options.sharpenM2 = jagged;
        } else {
          throw is.invalidParameterError('jagged', 'number between 0 and 10000', jagged);
        }
      }
    } else if (is.plainObject(options)) {
      if (is.number(options.sigma) && is.inRange(options.sigma, 0.000001, 10)) {
        this.options.sharpenSigma = options.sigma;
      } else {
        throw is.invalidParameterError('options.sigma', 'number between 0.000001 and 10', options.sigma);
      }
      if (is.defined(options.m1)) {
        if (is.number(options.m1) && is.inRange(options.m1, 0, 1000000)) {
          this.options.sharpenM1 = options.m1;
        } else {
          throw is.invalidParameterError('options.m1', 'number between 0 and 1000000', options.m1);
        }
      }
      if (is.defined(options.m2)) {
        if (is.number(options.m2) && is.inRange(options.m2, 0, 1000000)) {
          this.options.sharpenM2 = options.m2;
        } else {
          throw is.invalidParameterError('options.m2', 'number between 0 and 1000000', options.m2);
        }
      }
      if (is.defined(options.x1)) {
        if (is.number(options.x1) && is.inRange(options.x1, 0, 1000000)) {
          this.options.sharpenX1 = options.x1;
        } else {
          throw is.invalidParameterError('options.x1', 'number between 0 and 1000000', options.x1);
        }
      }
      if (is.defined(options.y2)) {
        if (is.number(options.y2) && is.inRange(options.y2, 0, 1000000)) {
          this.options.sharpenY2 = options.y2;
        } else {
          throw is.invalidParameterError('options.y2', 'number between 0 and 1000000', options.y2);
        }
      }
      if (is.defined(options.y3)) {
        if (is.number(options.y3) && is.inRange(options.y3, 0, 1000000)) {
          this.options.sharpenY3 = options.y3;
        } else {
          throw is.invalidParameterError('options.y3', 'number between 0 and 1000000', options.y3);
        }
      }
    } else {
      throw is.invalidParameterError('sigma', 'number between 0.01 and 10000', options);
    }
    return this;
  }
  
  /**
   * Apply median filter.
   * When used without parameters the default window is 3x3.
   *
   * @example
   * const output = await sharp(input).median().toBuffer();
   *
   * @example
   * const output = await sharp(input).median(5).toBuffer();
   *
   * @param {number} [size=3] square mask size: size x size
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function median (size) {
    if (!is.defined(size)) {
      // No arguments: default to 3x3
      this.options.medianSize = 3;
    } else if (is.integer(size) && is.inRange(size, 1, 1000)) {
      // Numeric argument: specific sigma
      this.options.medianSize = size;
    } else {
      throw is.invalidParameterError('size', 'integer between 1 and 1000', size);
    }
    return this;
  }
  
  /**
   * Blur the image.
   *
   * When used without parameters, performs a fast 3x3 box blur (equivalent to a box linear filter).
   *
   * When a `sigma` is provided, performs a slower, more accurate Gaussian blur.
   *
   * @example
   * const boxBlurred = await sharp(input)
   *   .blur()
   *   .toBuffer();
   *
   * @example
   * const gaussianBlurred = await sharp(input)
   *   .blur(5)
   *   .toBuffer();
   *
   * @param {Object|number|Boolean} [options]
   * @param {number} [options.sigma] a value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
   * @param {string} [options.precision='integer'] How accurate the operation should be, one of: integer, float, approximate.
   * @param {number} [options.minAmplitude=0.2] A value between 0.001 and 1. A smaller value will generate a larger, more accurate mask.
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function blur (options) {
    let sigma;
    if (is.number(options)) {
      sigma = options;
    } else if (is.plainObject(options)) {
      if (!is.number(options.sigma)) {
        throw is.invalidParameterError('options.sigma', 'number between 0.3 and 1000', sigma);
      }
      sigma = options.sigma;
      if ('precision' in options) {
        if (is.string(vipsPrecision[options.precision])) {
          this.options.precision = vipsPrecision[options.precision];
        } else {
          throw is.invalidParameterError('precision', 'one of: integer, float, approximate', options.precision);
        }
      }
      if ('minAmplitude' in options) {
        if (is.number(options.minAmplitude) && is.inRange(options.minAmplitude, 0.001, 1)) {
          this.options.minAmpl = options.minAmplitude;
        } else {
          throw is.invalidParameterError('minAmplitude', 'number between 0.001 and 1', options.minAmplitude);
        }
      }
    }
  
    if (!is.defined(options)) {
      // No arguments: default to mild blur
      this.options.blurSigma = -1;
    } else if (is.bool(options)) {
      // Boolean argument: apply mild blur?
      this.options.blurSigma = options ? -1 : 0;
    } else if (is.number(sigma) && is.inRange(sigma, 0.3, 1000)) {
      // Numeric argument: specific sigma
      this.options.blurSigma = sigma;
    } else {
      throw is.invalidParameterError('sigma', 'number between 0.3 and 1000', sigma);
    }
  
    return this;
  }
  
  /**
   * Expand foreground objects using the dilate morphological operator.
   *
   * @example
   * const output = await sharp(input)
   *   .dilate()
   *   .toBuffer();
   *
   * @param {Number} [width=1] dilation width in pixels.
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function dilate (width) {
    if (!is.defined(width)) {
      this.options.dilateWidth = 1;
    } else if (is.integer(width) && width > 0) {
      this.options.dilateWidth = width;
    } else {
      throw is.invalidParameterError('dilate', 'positive integer', dilate);
    }
    return this;
  }
  
  /**
   * Shrink foreground objects using the erode morphological operator.
   *
   * @example
   * const output = await sharp(input)
   *   .erode()
   *   .toBuffer();
   *
   * @param {Number} [width=1] erosion width in pixels.
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function erode (width) {
    if (!is.defined(width)) {
      this.options.erodeWidth = 1;
    } else if (is.integer(width) && width > 0) {
      this.options.erodeWidth = width;
    } else {
      throw is.invalidParameterError('erode', 'positive integer', erode);
    }
    return this;
  }
  
  /**
   * Merge alpha transparency channel, if any, with a background, then remove the alpha channel.
   *
   * See also {@link /api-channel#removealpha removeAlpha}.
   *
   * @example
   * await sharp(rgbaInput)
   *   .flatten({ background: '#F0A703' })
   *   .toBuffer();
   *
   * @param {Object} [options]
   * @param {string|Object} [options.background={r: 0, g: 0, b: 0}] - background colour, parsed by the [color](https://www.npmjs.org/package/color) module, defaults to black.
   * @returns {Sharp}
   */
  function flatten (options) {
    this.options.flatten = is.bool(options) ? options : true;
    if (is.object(options)) {
      this._setBackgroundColourOption('flattenBackground', options.background);
    }
    return this;
  }
  
  /**
   * Ensure the image has an alpha channel
   * with all white pixel values made fully transparent.
   *
   * Existing alpha channel values for non-white pixels remain unchanged.
   *
   * This feature is experimental and the API may change.
   *
   * @since 0.32.1
   *
   * @example
   * await sharp(rgbInput)
   *   .unflatten()
   *   .toBuffer();
   *
   * @example
   * await sharp(rgbInput)
   *   .threshold(128, { grayscale: false }) // converter bright pixels to white
   *   .unflatten()
   *   .toBuffer();
   */
  function unflatten () {
    this.options.unflatten = true;
    return this;
  }
  
  /**
   * Apply a gamma correction by reducing the encoding (darken) pre-resize at a factor of `1/gamma`
   * then increasing the encoding (brighten) post-resize at a factor of `gamma`.
   * This can improve the perceived brightness of a resized image in non-linear colour spaces.
   * JPEG and WebP input images will not take advantage of the shrink-on-load performance optimisation
   * when applying a gamma correction.
   *
   * Supply a second argument to use a different output gamma value, otherwise the first value is used in both cases.
   *
   * @param {number} [gamma=2.2] value between 1.0 and 3.0.
   * @param {number} [gammaOut] value between 1.0 and 3.0. (optional, defaults to same as `gamma`)
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function gamma (gamma, gammaOut) {
    if (!is.defined(gamma)) {
      // Default gamma correction of 2.2 (sRGB)
      this.options.gamma = 2.2;
    } else if (is.number(gamma) && is.inRange(gamma, 1, 3)) {
      this.options.gamma = gamma;
    } else {
      throw is.invalidParameterError('gamma', 'number between 1.0 and 3.0', gamma);
    }
    if (!is.defined(gammaOut)) {
      // Default gamma correction for output is same as input
      this.options.gammaOut = this.options.gamma;
    } else if (is.number(gammaOut) && is.inRange(gammaOut, 1, 3)) {
      this.options.gammaOut = gammaOut;
    } else {
      throw is.invalidParameterError('gammaOut', 'number between 1.0 and 3.0', gammaOut);
    }
    return this;
  }
  
  /**
   * Produce the "negative" of the image.
   *
   * @example
   * const output = await sharp(input)
   *   .negate()
   *   .toBuffer();
   *
   * @example
   * const output = await sharp(input)
   *   .negate({ alpha: false })
   *   .toBuffer();
   *
   * @param {Object} [options]
   * @param {Boolean} [options.alpha=true] Whether or not to negate any alpha channel
   * @returns {Sharp}
   */
  function negate (options) {
    this.options.negate = is.bool(options) ? options : true;
    if (is.plainObject(options) && 'alpha' in options) {
      if (!is.bool(options.alpha)) {
        throw is.invalidParameterError('alpha', 'should be boolean value', options.alpha);
      } else {
        this.options.negateAlpha = options.alpha;
      }
    }
    return this;
  }
  
  /**
   * Enhance output image contrast by stretching its luminance to cover a full dynamic range.
   *
   * Uses a histogram-based approach, taking a default range of 1% to 99% to reduce sensitivity to noise at the extremes.
   *
   * Luminance values below the `lower` percentile will be underexposed by clipping to zero.
   * Luminance values above the `upper` percentile will be overexposed by clipping to the max pixel value.
   *
   * @example
   * const output = await sharp(input)
   *   .normalise()
   *   .toBuffer();
   *
   * @example
   * const output = await sharp(input)
   *   .normalise({ lower: 0, upper: 100 })
   *   .toBuffer();
   *
   * @param {Object} [options]
   * @param {number} [options.lower=1] - Percentile below which luminance values will be underexposed.
   * @param {number} [options.upper=99] - Percentile above which luminance values will be overexposed.
   * @returns {Sharp}
   */
  function normalise (options) {
    if (is.plainObject(options)) {
      if (is.defined(options.lower)) {
        if (is.number(options.lower) && is.inRange(options.lower, 0, 99)) {
          this.options.normaliseLower = options.lower;
        } else {
          throw is.invalidParameterError('lower', 'number between 0 and 99', options.lower);
        }
      }
      if (is.defined(options.upper)) {
        if (is.number(options.upper) && is.inRange(options.upper, 1, 100)) {
          this.options.normaliseUpper = options.upper;
        } else {
          throw is.invalidParameterError('upper', 'number between 1 and 100', options.upper);
        }
      }
    }
    if (this.options.normaliseLower >= this.options.normaliseUpper) {
      throw is.invalidParameterError('range', 'lower to be less than upper',
        `${this.options.normaliseLower} >= ${this.options.normaliseUpper}`);
    }
    this.options.normalise = true;
    return this;
  }
  
  /**
   * Alternative spelling of normalise.
   *
   * @example
   * const output = await sharp(input)
   *   .normalize()
   *   .toBuffer();
   *
   * @param {Object} [options]
   * @param {number} [options.lower=1] - Percentile below which luminance values will be underexposed.
   * @param {number} [options.upper=99] - Percentile above which luminance values will be overexposed.
   * @returns {Sharp}
   */
  function normalize (options) {
    return this.normalise(options);
  }
  
  /**
   * Perform contrast limiting adaptive histogram equalization
   * {@link https://en.wikipedia.org/wiki/Adaptive_histogram_equalization#Contrast_Limited_AHE CLAHE}.
   *
   * This will, in general, enhance the clarity of the image by bringing out darker details.
   *
   * @since 0.28.3
   *
   * @example
   * const output = await sharp(input)
   *   .clahe({
   *     width: 3,
   *     height: 3,
   *   })
   *   .toBuffer();
   *
   * @param {Object} options
   * @param {number} options.width - Integral width of the search window, in pixels.
   * @param {number} options.height - Integral height of the search window, in pixels.
   * @param {number} [options.maxSlope=3] - Integral level of brightening, between 0 and 100, where 0 disables contrast limiting.
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function clahe (options) {
    if (is.plainObject(options)) {
      if (is.integer(options.width) && options.width > 0) {
        this.options.claheWidth = options.width;
      } else {
        throw is.invalidParameterError('width', 'integer greater than zero', options.width);
      }
      if (is.integer(options.height) && options.height > 0) {
        this.options.claheHeight = options.height;
      } else {
        throw is.invalidParameterError('height', 'integer greater than zero', options.height);
      }
      if (is.defined(options.maxSlope)) {
        if (is.integer(options.maxSlope) && is.inRange(options.maxSlope, 0, 100)) {
          this.options.claheMaxSlope = options.maxSlope;
        } else {
          throw is.invalidParameterError('maxSlope', 'integer between 0 and 100', options.maxSlope);
        }
      }
    } else {
      throw is.invalidParameterError('options', 'plain object', options);
    }
    return this;
  }
  
  /**
   * Convolve the image with the specified kernel.
   *
   * @example
   * sharp(input)
   *   .convolve({
   *     width: 3,
   *     height: 3,
   *     kernel: [-1, 0, 1, -2, 0, 2, -1, 0, 1]
   *   })
   *   .raw()
   *   .toBuffer(function(err, data, info) {
   *     // data contains the raw pixel data representing the convolution
   *     // of the input image with the horizontal Sobel operator
   *   });
   *
   * @param {Object} kernel
   * @param {number} kernel.width - width of the kernel in pixels.
   * @param {number} kernel.height - height of the kernel in pixels.
   * @param {Array<number>} kernel.kernel - Array of length `width*height` containing the kernel values.
   * @param {number} [kernel.scale=sum] - the scale of the kernel in pixels.
   * @param {number} [kernel.offset=0] - the offset of the kernel in pixels.
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function convolve (kernel) {
    if (!is.object(kernel) || !Array.isArray(kernel.kernel) ||
        !is.integer(kernel.width) || !is.integer(kernel.height) ||
        !is.inRange(kernel.width, 3, 1001) || !is.inRange(kernel.height, 3, 1001) ||
        kernel.height * kernel.width !== kernel.kernel.length
    ) {
      // must pass in a kernel
      throw new Error('Invalid convolution kernel');
    }
    // Default scale is sum of kernel values
    if (!is.integer(kernel.scale)) {
      kernel.scale = kernel.kernel.reduce((a, b) => a + b, 0);
    }
    // Clip scale to a minimum value of 1
    if (kernel.scale < 1) {
      kernel.scale = 1;
    }
    if (!is.integer(kernel.offset)) {
      kernel.offset = 0;
    }
    this.options.convKernel = kernel;
    return this;
  }
  
  /**
   * Any pixel value greater than or equal to the threshold value will be set to 255, otherwise it will be set to 0.
   * @param {number} [threshold=128] - a value in the range 0-255 representing the level at which the threshold will be applied.
   * @param {Object} [options]
   * @param {Boolean} [options.greyscale=true] - convert to single channel greyscale.
   * @param {Boolean} [options.grayscale=true] - alternative spelling for greyscale.
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function threshold (threshold, options) {
    if (!is.defined(threshold)) {
      this.options.threshold = 128;
    } else if (is.bool(threshold)) {
      this.options.threshold = threshold ? 128 : 0;
    } else if (is.integer(threshold) && is.inRange(threshold, 0, 255)) {
      this.options.threshold = threshold;
    } else {
      throw is.invalidParameterError('threshold', 'integer between 0 and 255', threshold);
    }
    if (!is.object(options) || options.greyscale === true || options.grayscale === true) {
      this.options.thresholdGrayscale = true;
    } else {
      this.options.thresholdGrayscale = false;
    }
    return this;
  }
  
  /**
   * Perform a bitwise boolean operation with operand image.
   *
   * This operation creates an output image where each pixel is the result of
   * the selected bitwise boolean `operation` between the corresponding pixels of the input images.
   *
   * @param {Buffer|string} operand - Buffer containing image data or string containing the path to an image file.
   * @param {string} operator - one of `and`, `or` or `eor` to perform that bitwise operation, like the C logic operators `&`, `|` and `^` respectively.
   * @param {Object} [options]
   * @param {Object} [options.raw] - describes operand when using raw pixel data.
   * @param {number} [options.raw.width]
   * @param {number} [options.raw.height]
   * @param {number} [options.raw.channels]
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function boolean (operand, operator, options) {
    this.options.boolean = this._createInputDescriptor(operand, options);
    if (is.string(operator) && is.inArray(operator, ['and', 'or', 'eor'])) {
      this.options.booleanOp = operator;
    } else {
      throw is.invalidParameterError('operator', 'one of: and, or, eor', operator);
    }
    return this;
  }
  
  /**
   * 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 = [];
    } 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', 'number or array of numbers', a);
    }
    if (!is.defined(b)) {
      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', '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;
  }
  
  /**
   * Recombine the image with the specified matrix.
   *
   * @since 0.21.1
   *
   * @example
   * sharp(input)
   *   .recomb([
   *    [0.3588, 0.7044, 0.1368],
   *    [0.2990, 0.5870, 0.1140],
   *    [0.2392, 0.4696, 0.0912],
   *   ])
   *   .raw()
   *   .toBuffer(function(err, data, info) {
   *     // data contains the raw pixel data after applying the matrix
   *     // With this example input, a sepia filter has been applied
   *   });
   *
   * @param {Array<Array<number>>} inputMatrix - 3x3 or 4x4 Recombination matrix
   * @returns {Sharp}
   * @throws {Error} Invalid parameters
   */
  function recomb (inputMatrix) {
    if (!Array.isArray(inputMatrix)) {
      throw is.invalidParameterError('inputMatrix', 'array', inputMatrix);
    }
    if (inputMatrix.length !== 3 && inputMatrix.length !== 4) {
      throw is.invalidParameterError('inputMatrix', '3x3 or 4x4 array', inputMatrix.length);
    }
    const recombMatrix = inputMatrix.flat().map(Number);
    if (recombMatrix.length !== 9 && recombMatrix.length !== 16) {
      throw is.invalidParameterError('inputMatrix', 'cardinality of 9 or 16', recombMatrix.length);
    }
    this.options.recombMatrix = recombMatrix;
    return this;
  }
  
  /**
   * Transforms the image using brightness, saturation, hue rotation, and lightness.
   * Brightness and lightness both operate on luminance, with the difference being that
   * brightness is multiplicative whereas lightness is additive.
   *
   * @since 0.22.1
   *
   * @example
   * // increase brightness by a factor of 2
   * const output = await sharp(input)
   *   .modulate({
   *     brightness: 2
   *   })
   *   .toBuffer();
   *
   * @example
   * // hue-rotate by 180 degrees
   * const output = await sharp(input)
   *   .modulate({
   *     hue: 180
   *   })
   *   .toBuffer();
   *
   * @example
   * // increase lightness by +50
   * const output = await sharp(input)
   *   .modulate({
   *     lightness: 50
   *   })
   *   .toBuffer();
   *
   * @example
   * // decrease brightness and saturation while also hue-rotating by 90 degrees
   * const output = await sharp(input)
   *   .modulate({
   *     brightness: 0.5,
   *     saturation: 0.5,
   *     hue: 90,
   *   })
   *   .toBuffer();
   *
   * @param {Object} [options]
   * @param {number} [options.brightness] Brightness multiplier
   * @param {number} [options.saturation] Saturation multiplier
   * @param {number} [options.hue] Degrees for hue rotation
   * @param {number} [options.lightness] Lightness addend
   * @returns {Sharp}
   */
  function modulate (options) {
    if (!is.plainObject(options)) {
      throw is.invalidParameterError('options', 'plain object', options);
    }
    if ('brightness' in options) {
      if (is.number(options.brightness) && options.brightness >= 0) {
        this.options.brightness = options.brightness;
      } else {
        throw is.invalidParameterError('brightness', 'number above zero', options.brightness);
      }
    }
    if ('saturation' in options) {
      if (is.number(options.saturation) && options.saturation >= 0) {
        this.options.saturation = options.saturation;
      } else {
        throw is.invalidParameterError('saturation', 'number above zero', options.saturation);
      }
    }
    if ('hue' in options) {
      if (is.integer(options.hue)) {
        this.options.hue = options.hue % 360;
      } else {
        throw is.invalidParameterError('hue', 'number', options.hue);
      }
    }
    if ('lightness' in options) {
      if (is.number(options.lightness)) {
        this.options.lightness = options.lightness;
      } else {
        throw is.invalidParameterError('lightness', 'number', options.lightness);
      }
    }
    return this;
  }
  
  /**
   * Decorate the Sharp prototype with operation-related functions.
   * @module Sharp
   * @private
   */
  module.exports = (Sharp) => {
    Object.assign(Sharp.prototype, {
      autoOrient,
      rotate,
      flip,
      flop,
      affine,
      sharpen,
      erode,
      dilate,
      median,
      blur,
      flatten,
      unflatten,
      gamma,
      negate,
      normalise,
      normalize,
      clahe,
      convolve,
      threshold,
      boolean,
      linear,
      recomb,
      modulate
    });
  };
  