What will you learn in this post?

This post introduces how to use JavaScript to upload a single image with dat.GUI.


dat.GUI is a lightweight controller library for JavaScript, which I think is a quite nice and elegant GUI.

To use dat.GUI, you need to create an object containing the parameters you want, and then add it to the GUI.

var GuiConfig = function() {
    this['Vertex Cnt'] = 1000;  // default number value

    this['Edge Weight'] = 0.8;  // default number value

    this['Apply'] = function() {  // the function will be called

        console.log('apply!');    // when `Apply` is clicked

var config = new GuiConfig();

var gui = new dat.GUI();
gui.add(config, 'Vertex Cnt', 100, 5000).step(100);  // number range and step

gui.add(config, 'Edge Weight', 0, 1).step(0.05);  // number range and step

gui.add(config, 'Apply');  // add a function button

The Real Magic

Two elements are to be added to dat.GUI, a function element as button to trigger file explorer, and a label element to display the file name of the chosen image.

var GuiConfig = function() {
    this['Image Path'] = '18.jpg';  // default image path

    this['Upload Image'] = function() {
        // you need to create an input element in HTML, explained later

        var input = document.getElementById('img-path');
        input.addEventListener('change', function() {
            var file = input.files[0];
            config['Image Path'] = file.name;
            // update all controllers

            for (var i in gui.__controllers) {
var config = new GuiConfig();
gui.add(config, 'Image Path', config['Image Path']);
gui.add(config, 'Upload Image');

We also need to add another <input> in the HTML with the type of file, which is the real magic to load file explorer.

<input id="img-path" type="file" />

And use CSS to hide it, cause it’s magic!!!

#img-path {
    display: none;

Under The Hood

The user need to click the Upload Image button, which is a function element, and it will add a change event listener to a file input element. And then the input click event is triggered, so that user can choose an image in file explorer, and the change event will then be triggered. In the change event, dat.GUI is to be updated according to the file name of the input image.

And that’s how our magic works.

Hope you enjoyed it! :smiley: