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 length = bytes.length;
  for (let i = 3; i < length; i += 4) {
    const alpha = bytes[i];
    if (alpha === 0) {
      bytes[i - 3] = r0;
      bytes[i - 2] = g0;
      bytes[i - 1] = b0;
    } else if (alpha < 255) {
      const alpha_ = 255 - alpha;
      bytes[i - 3] = (bytes[i - 3] * alpha + r0 * alpha_) >> 8;
      bytes[i - 2] = (bytes[i - 2] * alpha + g0 * alpha_) >> 8;
      bytes[i - 1] = (bytes[i - 1] * alpha + b0 * alpha_) >> 8;
    }
  }
}
function composeSMaskAlpha(maskData, layerData, transferMap) {