Add alpha channel to Unit8ClampedArray

gistfile1.txt

function addAlphaChannelToUnit8ClampedArray(unit8Array: Uint8ClampedArray, imageWidth: number, imageHeight: number) {
    const newImageData = new Uint8ClampedArray(imageWidth * imageHeight * 4);

    for (let j = 0, k = 0, jj = imageWidth * imageHeight * 4; j < jj; ) {
      newImageData[j++] = unit8Array[k++];
      newImageData[j++] = unit8Array[k++];
      newImageData[j++] = unit8Array[k++];
      newImageData[j++] = 255;
    }

    return newImageData;
  }