hello,
this pdf file created with Adobe InDesign, alot of elements are missing, also wrong color are displaying:
http://tal-ram.co.il/images/products/orders/14265798291.pdf

![viewer](https://cloud.githubusercontent.com/assets/1198143/6713275/f88ae242-cd99-11e4-8202-fdb5dc4b132e.png)

![org](https://cloud.githubusercontent.com/assets/1198143/6713312/24d83ff2-cd9a-11e4-82e7-647ad5440a64.png)

maskCtx,
  layerCtx,
  width,
  height,
  subtype,
  backdrop,
  transferMap
) {
  const hasBackdrop = !!backdrop;
  const r0 = hasBackdrop ? backdrop[0] : 0;
  const g0 = hasBackdrop ? backdrop[1] : 0;
  const b0 = hasBackdrop ? backdrop[2] : 0;
  let composeFn;
  if (subtype === "Luminosity") {
    composeFn = composeSMaskLuminosity;
  } else {
    composeFn = composeSMaskAlpha;
  }
  
  const PIXELS_TO_PROCESS = 1048576;
  const chunkSize = Math.min(height, Math.ceil(PIXELS_TO_PROCESS / width));
  for (let row = 0; row < height; row += chunkSize) {
    const chunkHeight = Math.min(chunkSize, height - row);
    const maskData = maskCtx.getImageData(0, row, width, chunkHeight);
    const layerData = layerCtx.getImageData(0, row, width, chunkHeight);