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node_modules/pngjs/lib/bitpacker.js

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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;
+  if (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
+    if (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;
+};