**Link to PDF file (or attach file here):**
[tocheckFile.pdf](https://github.com/mozilla/pdf.js/files/240714/tocheckFile.pdf)

**Configuration:**
- Web browser and its version: FF45.0.2, Chrome Version 50.0.2661.86 (64-bit) 
- Operating system and its version: Mac OSX El Capitan

**\- PDF.js version:**
PDFJS.version = '1.1.215';
PDFJS.build = 'c9a7498';

**Steps to reproduce the problem:**
1. Use the lib to generate a PDF preview.

**What is the expected behavior? (add screenshot)**
PDF preview should have rendered completely. (frog head should be complete)

**What went wrong? (add screenshot)**
<img width="952" alt="imagesnotrenderinginpreview" src="https://cloud.githubusercontent.com/assets/10231850/14889265/cecb2d64-0d66-11e6-98e1-da2d39728552.png">

See attached screenshot in regards to the pdf file

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

const length = maskData.length;
  const scale = 1 / 255;
  for (let i = 3; i < length; i += 4) {
    const alpha = transferMap ? transferMap[maskData[i]] : maskData[i];
    layerData[i] = (layerData[i] * alpha * scale) | 0;
  }
}
function composeSMaskLuminosity(maskData, layerData, transferMap) {
  const length = maskData.length;
  for (let i = 3; i < length; i += 4) {
    const y =
      maskData[i - 3] * 77 + 
      maskData[i - 2] * 152 + 
      maskData[i - 1] * 28; 
    layerData[i] = transferMap
      ? (layerData[i] * transferMap[y >> 8]) >> 8
      : (layerData[i] * y) >> 16;
  }
}
function genericComposeSMask(