Cystoscape, trying to display images instead of nodes

I'm trying to display images instead of nodes using Cytoscape.js to create a network diagram, but I haven't had any success yet. I started with the Images and breadthfirst example (https://gist.github.com/maxkfranz/aedff159b0df05ccfaa5), but there are a couple key things I would like to change.

For starters, I'd like to display an image only instead of a node. The above example displays a circle node with an image inside it. Is there any way to make the node completely transparent, and just let the image show through? I just want to see my vector icon images. When I delete all style properties for my node selector except width and height, I still see a circle constraining my image. I just want to see my image.

Next, I'd like to use something on the element data to decide what image to use instead of the #nodeId mechanism in the example above.

.selector('#order-db')
      .css({
        'background-image': 'https://farm8.staticflickr.com/7272/7633179468_3e19e45a0c_b.jpg'
      })

Using a unique selector for each id is not very scalable or easy to modify. I'd prefer a declarative approach where a property on the data element determines which image to display. I tried using the "classes" property on an element, and I added a "shape-database" value to it. Here is how the class is defined...

.shape-database {
    width: 95px;
    height: 95px;
    /*background: url('images/network-icons.jpg') 0px -95px;*/
    background: url('images/database-5-med.png');
}

I then tested that the "shape-database" class was working by adding a simple div to the page, and the class is working properly on a normal div. The cyto node I added the classes property to does not display the background image. It's as if the class was not applied to the node, or else the node is blocking the image somehow. This is with the exact same code I was using above, with all the node selector css properties removed except width and height, and the #order-db css selector removed. I just see a grey circle for the node.

When the classes property on the element didn't work, I even tried the following to no avail...

cy.$('#order-db').addClass('shape-database');

Any thoughts on what I'm doing wrong? A link to an example displaying just images instead of nodes would help as well.

Solution

Displaying an image instead of a node:

The key here was in hiding the node background and border completely, so that the background image alone shows through. The key to accomplishing that is through "background-opacity" and "border-opacity" (or "border-width") on the style objects. I added an image property (value is an img src) to the data object for each element that I wanted to swap out with an image, as well as the following style.

{
    selector: 'node[image]',
    style: {
        'background-image': 'data(image)', // specify some image
        'background-opacity': 0, // do not show the bg colour
        'border-width': 0, // no border that would increase node size
        'background-clip': 'none' // let image go beyond node shape (also better performance)
    }
}

This also satisfied my requirement to use the element data to designate which elements are to be replaced with images and which images to use, instead of hard-coding a unique style and image for each element id.

I never got the classes data property to have any effect whatsoever on the background-image of a node. Perhaps there's a bug there.

Hopefully, this will help someone in the future because it was not obvious to me that background-opacity etc. made the entire node invisible. From the documentation, it sounded like it affected the node's background. Knowing that I was altering the background image for the node caused me quite a bit of confusion around nodes and backgrounds. I'm still quite fuzzy on all the layers and how they interact, but the above works and is better in my opinion than the image example given on the cytoscape site.