export function fromWhiteIsZero(raster, max) {
  const { width, height } = raster;
  const rgbRaster = new Uint8Array(width * height * 3);
  let value;
  for (let i = 0, j = 0; i < raster.length; ++i, j += 3) {
    value = 256 - (raster[i] / max * 256);
    rgbRaster[j] = value;
    rgbRaster[j + 1] = value;
    rgbRaster[j + 2] = value;
  }
  return rgbRaster;
}

export function fromBlackIsZero(raster, max) {
  const { width, height } = raster;
  const rgbRaster = new Uint8Array(width * height * 3);
  let value;
  for (let i = 0, j = 0; i < raster.length; ++i, j += 3) {
    value = raster[i] / max * 256;
    rgbRaster[j] = value;
    rgbRaster[j + 1] = value;
    rgbRaster[j + 2] = value;
  }
  return rgbRaster;
}

export function fromPalette(raster, colorMap) {
  const { width, height } = raster;
  const rgbRaster = new Uint8Array(width * height * 3);
  const greenOffset = colorMap.length / 3;
  const blueOffset = colorMap.length / 3 * 2;
  for (let i = 0, j = 0; i < raster.length; ++i, j += 3) {
    const mapIndex = raster[i];
    rgbRaster[j] = colorMap[mapIndex] / 65536 * 256;
    rgbRaster[j + 1] = colorMap[mapIndex + greenOffset] / 65536 * 256;
    rgbRaster[j + 2] = colorMap[mapIndex + blueOffset] / 65536 * 256;
  }
  return rgbRaster;
}

export function fromCMYK(cmykRaster) {
  const { width, height } = cmykRaster;
  const rgbRaster = new Uint8Array(width * height * 3);
  for (let i = 0, j = 0; i < cmykRaster.length; i += 4, j += 3) {
    const c = cmykRaster[i];
    const m = cmykRaster[i + 1];
    const y = cmykRaster[i + 2];
    const k = cmykRaster[i + 3];

    rgbRaster[j] = 255 * ((255 - c) / 256) * ((255 - k) / 256);
    rgbRaster[j + 1] = 255 * ((255 - m) / 256) * ((255 - k) / 256);
    rgbRaster[j + 2] = 255 * ((255 - y) / 256) * ((255 - k) / 256);
  }
  return rgbRaster;
}

export function fromYCbCr(yCbCrRaster) {
  const { width, height } = yCbCrRaster;
  const rgbRaster = new Uint8ClampedArray(width * height * 3);
  for (let i = 0, j = 0; i < yCbCrRaster.length; i += 3, j += 3) {
    const y = yCbCrRaster[i];
    const cb = yCbCrRaster[i + 1];
    const cr = yCbCrRaster[i + 2];

    rgbRaster[j] = (y + (1.40200 * (cr - 0x80)));
    rgbRaster[j + 1] = (y - (0.34414 * (cb - 0x80)) - (0.71414 * (cr - 0x80)));
    rgbRaster[j + 2] = (y + (1.77200 * (cb - 0x80)));
  }
  return rgbRaster;
}

const Xn = 0.95047;
const Yn = 1.00000;
const Zn = 1.08883;

// from https://github.com/antimatter15/rgb-lab/blob/master/color.js

export function fromCIELab(cieLabRaster) {
  const { width, height } = cieLabRaster;
  const rgbRaster = new Uint8Array(width * height * 3);

  for (let i = 0, j = 0; i < cieLabRaster.length; i += 3, j += 3) {
    const L = cieLabRaster[i + 0];
    const a_ = cieLabRaster[i + 1] << 24 >> 24; // conversion from uint8 to int8
    const b_ = cieLabRaster[i + 2] << 24 >> 24; // same

    let y = (L + 16) / 116;
    let x = (a_ / 500) + y;
    let z = y - (b_ / 200);
    let r;
    let g;
    let b;

    x = Xn * ((x * x * x > 0.008856) ? x * x * x : (x - (16 / 116)) / 7.787);
    y = Yn * ((y * y * y > 0.008856) ? y * y * y : (y - (16 / 116)) / 7.787);
    z = Zn * ((z * z * z > 0.008856) ? z * z * z : (z - (16 / 116)) / 7.787);

    r = (x * 3.2406) + (y * -1.5372) + (z * -0.4986);
    g = (x * -0.9689) + (y * 1.8758) + (z * 0.0415);
    b = (x * 0.0557) + (y * -0.2040) + (z * 1.0570);

    r = (r > 0.0031308) ? ((1.055 * (r ** (1 / 2.4))) - 0.055) : 12.92 * r;
    g = (g > 0.0031308) ? ((1.055 * (g ** (1 / 2.4))) - 0.055) : 12.92 * g;
    b = (b > 0.0031308) ? ((1.055 * (b ** (1 / 2.4))) - 0.055) : 12.92 * b;

    rgbRaster[j] = Math.max(0, Math.min(1, r)) * 255;
    rgbRaster[j + 1] = Math.max(0, Math.min(1, g)) * 255;
    rgbRaster[j + 2] = Math.max(0, Math.min(1, b)) * 255;
  }
  return rgbRaster;
}