How to preload images using dropzone.js?

@dana 

To preload images using Dropzone.js, you can use the createThumbnail event provided by the library. Here's a step-by-step guide on how to preload images using Dropzone.js:

1. First, include the Dropzone.js library in your HTML file:

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<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/dropzone/5.7.2/min/dropzone.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/dropzone/5.7.2/min/dropzone.min.js"></script>

1. Set up a Dropzone instance on your HTML page:

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<form action="/upload" class="dropzone" id="myDropzone"></form>

1. Initialize the Dropzone instance and listen for the createThumbnail event:

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var myDropzone = new Dropzone("#myDropzone", {
  url: "/upload",
  paramName: "file",
});

myDropzone.on("createThumbnail", function (file, dataUrl) {
  // Preload each image by setting a new data URL
  var newFile = {
    size: file.size,
    type: file.type,
    name: file.name,
    status: Dropzone.ADDED,
    accepted: true,
    upload: {
      dataURL: dataUrl
    }
  };
  
  this.emit("addedfile", newFile);
  this.files.push(newFile);
  this.emit("thumbnail", newFile, dataUrl);
});

1. Now, you can preload images using the createThumbnail event. When a new file is added to the Dropzone instance, the createThumbnail event will be triggered and you can set a new data URL for the image to preload it.
2. You can also customize the behavior of the preloaded images by modifying the newFile object before adding it to the Dropzone instance.

By following these steps, you can preload images using Dropzone.js and customize the behavior of the preloaded images as needed.