This is a regression from #12864. The underscore is now too thin when the document is zoomed in.

URL: https://github.com/mozilla/pdf.js/files/2321540/issue6127.pdf
PDF.js 2.7.526: https://i.imgur.com/T4mIpct.png
PDF.js 2.7.510: https://i.imgur.com/nbwEpGT.png
Adobe Acrobat Reader DC 2020.013.20074: https://i.imgur.com/wDFBf3R.png

The screenshots were taken at 400% zoom.
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      if (this.imageLayer) {
        const position = this.getCanvasPosition(entry.x, entry.y);
        this.imageLayer.appendImage({
          imgData,
          left: position[0],
          top: position[1],
          width: w,
          height: h,
        });
      }
      ctx.restore();
    }
    this.compose();
  }
  paintSolidColorImageMask() {
    if (!this.contentVisible) {
      return;
    }
    this.ctx.fillRect(0, 0, 1, 1);
    this.compose();
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  markPoint(tag) {
    
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  markPointProps(tag, properties) {
    
  }
  beginMarkedContent(tag) {