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.
const scaled = this._scaleImage(imgToPaint, ctx.mozCurrentTransformInverse);
    ctx.imageSmoothingEnabled = getImageSmoothingEnabled(
      ctx.mozCurrentTransform,
      imgData.interpolate
    );
    ctx.drawImage(
      scaled.img,
      0,
      0,
      scaled.paintWidth,
      scaled.paintHeight,
      0,
      -height,
      width,
      height
    );
    if (this.imageLayer) {
      const position = this.getCanvasPosition(0, -height);
      this.imageLayer.appendImage({
        imgData,
        left: position[0],
        top: position[1],
        width: width / ctx.mozCurrentTransformInverse[0],
        height: height / ctx.mozCurrentTransformInverse[3],
      });
    }
    this.compose();
    this.restore();
  }
  paintInlineImageXObjectGroup(imgData, map) {