PDF.js displays blurry plots in PDF documents, e.g.

http://arxiv.org/pdf/1202.5344v1.pdf

When viewed in Chrome or Adobe Acrobat all the plots show sharp-edged squares. When viewed in Preview or PDF.js, all the squares show as blurry pixelated blobs.

const groupCtx = this.current.resumeSMaskCtx;
      const currentCtx = this.ctx;
      this.ctx = groupCtx;
      this.groupStack.push(currentCtx);
      this.groupLevel++;
    }
    endSMaskGroup() {