title: How do I use Fabricjs to change image color?
body: <p>I'm trying to use Fabric.js filters to change a single color of an image.  For example, I'm trying this to change the red parts of an image to green:</p>
  
  <pre><code>image.filters.push(new fabric.Image.filters.Blend({
      color: '#ff0000',
      mode: 'subtract'
  }));
  image.filters.push(new fabric.Image.filters.Blend({
      color: '#00ff00',
      mode: 'add'
  }));
  image.applyFilters(_canvas.renderAll.bind(_canvas));
  </code></pre>
  
  <p>But what is happening is that the black borders are all being changed to green as well.  Is there some way to do this using the built-in filters?</p>