Attach (recommended) or Link to PDF file here:
https://s3.eu-west-1.amazonaws.com/scai-dev.website.com/tmp/8ab8b56a-fa91-11eb-8d74-0242ac110004.pdf

Hi,
Please see an incorrect canvas rendering for the following document - page 9 specifically. It reproduces on https://mozilla.github.io/pdf.js/web/viewer.html (tried with Chrome). Other pages in this document look pretty much the same but the problem is on page 9 only.

Original screenshot:
![image](https://user-images.githubusercontent.com/23075641/129066656-7bb2fb56-2b88-4f40-8e67-b95bdeb9e521.png)


PDF JS:

![image](https://user-images.githubusercontent.com/23075641/129066734-56503a5c-413c-49c1-9e1c-470da3a642ed.png)

const height = imgData.height,
    width = imgData.width;
  const partialChunkHeight = height % FULL_CHUNK_HEIGHT;
  const fullChunks = (height - partialChunkHeight) / FULL_CHUNK_HEIGHT;
  const totalChunks = partialChunkHeight === 0 ? fullChunks : fullChunks + 1;
  const chunkImgData = ctx.createImageData(width, FULL_CHUNK_HEIGHT);
  let srcPos = 0;
  const src = imgData.data;
  const dest = chunkImgData.data;
  for (let i = 0; i < totalChunks; i++) {
    const thisChunkHeight =
      i < fullChunks ? FULL_CHUNK_HEIGHT : partialChunkHeight;
    
    
    let destPos = 3; 
    for (let j = 0; j < thisChunkHeight; j++) {
      let elem,
        mask = 0;
      for (let k = 0; k < width; k++) {
        if (!mask) {
          elem = src[srcPos++];
          mask = 128;
        }
        dest[destPos] = elem & mask ? 0 : 255;
        destPos += 4;
        mask >>= 1;