# All files bitpacker.js

11.36% Statements 10/88
6.12% Branches 3/49
66.67% Functions 2/3
11.63% Lines 10/86

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     "use strict";

    let constants = require("./constants");

    module.exports = function (dataIn, width, height, options) {
      let outHasAlpha =
        [constants.COLORTYPE_COLOR_ALPHA, constants.COLORTYPE_ALPHA].indexOf(
          options.colorType
        ) !== -1;
      Eif (options.colorType === options.inputColorType) {
        let bigEndian = (function () {
          let buffer = new ArrayBuffer(2);
          new DataView(buffer).setInt16(0, 256, true /* littleEndian */);
          // Int16Array uses the platform's endianness.
          return new Int16Array(buffer)[0] !== 256;
        })();
        // If no need to convert to grayscale and alpha is present/absent in both, take a fast route
        Eif (options.bitDepth === 8 || (options.bitDepth === 16 && bigEndian)) {
          return dataIn;
        }
      }

      // map to a UInt16 array if data is 16bit, fix endianness below
      let data = options.bitDepth !== 16 ? dataIn : new Uint16Array(dataIn.buffer);

      let maxValue = 255;
      let inBpp = constants.COLORTYPE_TO_BPP_MAP[options.inputColorType];
      if (inBpp === 4 && !options.inputHasAlpha) {
        inBpp = 3;
      }
      let outBpp = constants.COLORTYPE_TO_BPP_MAP[options.colorType];
      if (options.bitDepth === 16) {
        maxValue = 65535;
        outBpp *= 2;
      }
      let outData = Buffer.alloc(width * height * outBpp);

      let inIndex = 0;
      let outIndex = 0;

      let bgColor = options.bgColor || {};
      if (bgColor.red === undefined) {
        bgColor.red = maxValue;
      }
      if (bgColor.green === undefined) {
        bgColor.green = maxValue;
      }
      if (bgColor.blue === undefined) {
        bgColor.blue = maxValue;
      }

      function getRGBA() {
        let red;
        let green;
        let blue;
        let alpha = maxValue;
        switch (options.inputColorType) {
          case constants.COLORTYPE_COLOR_ALPHA:
            alpha = data[inIndex + 3];
            red = data[inIndex];
            green = data[inIndex + 1];
            blue = data[inIndex + 2];
            break;
          case constants.COLORTYPE_COLOR:
            red = data[inIndex];
            green = data[inIndex + 1];
            blue = data[inIndex + 2];
            break;
          case constants.COLORTYPE_ALPHA:
            alpha = data[inIndex + 1];
            red = data[inIndex];
            green = red;
            blue = red;
            break;
          case constants.COLORTYPE_GRAYSCALE:
            red = data[inIndex];
            green = red;
            blue = red;
            break;
          default:
            throw new Error(
              "input color type:" +
                options.inputColorType +
                " is not supported at present"
            );
        }

        if (options.inputHasAlpha) {
          if (!outHasAlpha) {
            alpha /= maxValue;
            red = Math.min(
              Math.max(Math.round((1 - alpha) * bgColor.red + alpha * red), 0),
              maxValue
            );
            green = Math.min(
              Math.max(Math.round((1 - alpha) * bgColor.green + alpha * green), 0),
              maxValue
            );
            blue = Math.min(
              Math.max(Math.round((1 - alpha) * bgColor.blue + alpha * blue), 0),
              maxValue
            );
          }
        }
        return { red: red, green: green, blue: blue, alpha: alpha };
      }

      for (let y = 0; y < height; y++) {
        for (let x = 0; x < width; x++) {
          let rgba = getRGBA(data, inIndex);

          switch (options.colorType) {
            case constants.COLORTYPE_COLOR_ALPHA:
            case constants.COLORTYPE_COLOR:
              if (options.bitDepth === 8) {
                outData[outIndex] = rgba.red;
                outData[outIndex + 1] = rgba.green;
                outData[outIndex + 2] = rgba.blue;
                if (outHasAlpha) {
                  outData[outIndex + 3] = rgba.alpha;
                }
              } else {
                outData.writeUInt16BE(rgba.red, outIndex);
                outData.writeUInt16BE(rgba.green, outIndex + 2);
                outData.writeUInt16BE(rgba.blue, outIndex + 4);
                if (outHasAlpha) {
                  outData.writeUInt16BE(rgba.alpha, outIndex + 6);
                }
              }
              break;
            case constants.COLORTYPE_ALPHA:
            case constants.COLORTYPE_GRAYSCALE: {
              // Convert to grayscale and alpha
              let grayscale = (rgba.red + rgba.green + rgba.blue) / 3;
              if (options.bitDepth === 8) {
                outData[outIndex] = grayscale;
                if (outHasAlpha) {
                  outData[outIndex + 1] = rgba.alpha;
                }
              } else {
                outData.writeUInt16BE(grayscale, outIndex);
                if (outHasAlpha) {
                  outData.writeUInt16BE(rgba.alpha, outIndex + 2);
                }
              }
              break;
            }
            default:
              throw new Error("unrecognised color Type " + options.colorType);
          }

          inIndex += inBpp;
          outIndex += outBpp;
        }
      }

      return outData;
    };