Using the Doka Image Editor Custom Element

The Custom Element and JavaScript approach are nearly identical but they do differ in two important ways.

  1. The Custom Element dispatches custom events. To prevent collisions with default events each event Doka Image Editor fires is prepended with 'doka:'. This means that the 'load' event is called 'doka:load'.

  2. The methods exposed by the JavaScript API allow passing a Doka Image Editor configuration object immediately on creation of each instance, this isn't possible with the Custom Element as it's instantiated by the DOM itself.

The Custom Element instance exposes the same properties, has the same methods, and fires the same events as the "normal" JavaScript instance.

We use the defineCustomElements method exported by the Doka Image Editor module. This makes it easy to define the Doka Image Editor element. When the returned Promise resolves the Custom Element is ready for use.

Using the <doka-image-editor/> element in our HTML looks like this.

<doka-image-editor src="my-image.jpeg"></doka-image-editor>

Now we use the defineCustomElements method to initialise it.

import { defineCustomElements } from './doka.js';

const elements = await defineCustomElements();

elements.forEach((editor) => {
    // `editor` is a reference to the <doka-image-editor/> element
});

We can also manually get a reference to an element if we already know it's ready.

const editor = document.querySelector('doka-image-editor');

Configuring the instance

With the editor logic installed we now need to load the plugins, the locale to use, and set the imageReader which is used to load images. Without these properties the editor won't load.

Doka Image Editor doesn't set any default values or labels, while this helps keep the library size as small as possible, it also means that we have to supply the default values and properties ourselves.

Let's start with registering the plugins using the setPlugins function. We'll then load the locale objects, finally we'll set the imageReader and the default plugin properties.

Registering plugins

Doka Image Editor uses plugins to render each util view. To get started we'll load the crop plugin, the finetune plugin, and the annotate plugin.

<!DOCTYPE html>

<link rel="stylesheet" href="doka.css" />

<doka-image-editor src="my-image.jpeg"></doka-image-editor>

<script type="module">
    import {
        // The method used to register the plugins
        setPlugins,

        // The plugins we want to use
        plugin_crop,
        plugin_finetune,
        plugin_annotate,
    } from 'doka.js';

    // This registers the plugins with Doka Image Editor
    setPlugins(plugin_crop, plugin_finetune, plugin_annotate);
</script>

Setting the locale object

Now we need to tell Doka Image Editor what labels and icons to use for all its UI controls. To do this we can import the English locale objects and assign them to the locale prop.

The Doka Image Editor module exports a core language file and a language file for each plugin. Currently only the English locale files are available in the package.

You can override the language files to show labels in a different language.

<!DOCTYPE html>

<link rel="stylesheet" href="doka.css" />

<doka-image-editor src="my-image.jpeg"></doka-image-editor>

<script type="module">
    import {
        // The method used to register the plugins
        setPlugins,

        // The method used to load the custom element
        defineCustomElements,

        // The plugins we want to use
        plugin_crop,
        plugin_finetune,
        plugin_annotate,

        // The main UI and plugin locale objects
        locale_en_gb,
        plugin_crop_locale_en_gb,
        plugin_finetune_locale_en_gb,
        plugin_annotate_locale_en_gb,

        // Because we use the annotate plugin we also need
        // to import the markup editor locale
        markup_editor_locale_en_gb,
    } from 'doka.js';

    // This registers the plugins with Doka Image Editor
    setPlugins(plugin_crop, plugin_finetune, plugin_annotate);

    // Merge all the locale objects
    const myLocale = {
        ...locale_en_gb,
        ...plugin_crop_locale_en_gb,
        ...plugin_finetune_locale_en_gb,
        ...plugin_annotate_locale_en_gb,
        ...markup_editor_locale_en_gb,
    };

    // Load the custom element
    const elements = await defineCustomElements();

    // Update the properties of each found editor element
    elements.forEach((editor) => {
        Object.assign(editor, {
            // Set locale
            locale: myLocale,
        });
    });
</script>

Changing labels can be done by updating existing locale properties or by creating a custom locale object.

// Merge all the locale objects
const myLocale = {
    ...locale_en_gb,
    ...plugin_crop_locale_en_gb,
    ...plugin_finetune_locale_en_gb,
    ...plugin_annotate_locale_en_gb,
    ...markup_editor_locale_en_gb,
};

// Change label of export button to 'Save'
myLocale.labelButtonExport = 'Save';

Setting the imageReader

The imageReader property expects a list of instructions that tells Doka Image Editor how to load images.

A default image reader is exported by the JavaScript module. It can read resources of type File, Blob, Data URL, URL, HTMLCanvasElement, and HTMLImageElement. It will also automatically correct mobile photo orientation when needed.

By default Doka Image Editor can read images that are supported by the clients browser. In general these image formats are supported by all major browsers.

  • image/gif
  • image/png
  • image/jpeg
  • image/webp
  • image/bmp
  • image/svg

If needed we can use the preprocessImageFile hook to extend the default image reader and load more image formats (for example HEIC).

Let's set the default imageReader property.

<!DOCTYPE html>

<link rel="stylesheet" href="doka.css" />

<doka-image-editor src="my-image.jpeg"></doka-image-editor>

<script type="module">
    import {
        // The method used to register the plugins
        setPlugins,

        // The plugins we want to use
        plugin_crop,
        plugin_finetune,
        plugin_annotate,

        // The method used to load the custom element
        defineCustomElements,

        // Import the default image reader
        createDefaultImageReader,

        // The main UI and plugin locale objects
        locale_en_gb,
        plugin_crop_locale_en_gb,
        plugin_finetune_locale_en_gb,
        plugin_annotate_locale_en_gb,

        // Because we use the annotate plugin we also need
        // to import the markup editor locale
        markup_editor_locale_en_gb,
    } from 'doka.js';

    // This registers the plugins with Doka Image Editor
    setPlugins(plugin_crop, plugin_finetune, plugin_annotate);

    // Merge all the locale objects
    const myLocale = {
        ...locale_en_gb,
        ...plugin_crop_locale_en_gb,
        ...plugin_finetune_locale_en_gb,
        ...plugin_annotate_locale_en_gb,
        ...markup_editor_locale_en_gb,
    };

    // Load the custom element
    const elements = await defineCustomElements();

    elements.forEach((editor) => {
        Object.assign(editor, {
            // Set default imageReader
            imageReader: createDefaultImageReader(),

            // Set locale
            locale: myLocale,
        });
    });
</script>

Doka Image Editor can now load images and render the user interface.

To show the default tools in the annotate view, and the finetune controls in the Finetune plugin we need to import the default properties.

Setting default plugin properties

The controls for the Finetune util as well as the Annotate util are still missing. That's because we have to set these manually.

We need to import markup_editor_defaults because the Annotate plugin uses the Markup Editor. And we import plugin_finetune_defaults to set the default color adjustment controls in the Finetune plugin.

Below we import both and assign the objects to the appendEditor options argument.

<!DOCTYPE html>

<link rel="stylesheet" href="doka.css" />

<doka-image-editor src="my-image.jpeg"></doka-image-editor>

<script type="module">
    import {
        // The method used to register the plugins
        setPlugins,

        // The plugins we want to use
        plugin_crop,
        plugin_finetune,
        plugin_annotate,

        // The method used to load the custom element
        defineCustomElements,

        // Import the default image reader
        createDefaultImageReader,

        // The main UI and plugin locale objects
        locale_en_gb,
        plugin_crop_locale_en_gb,
        plugin_finetune_locale_en_gb,
        plugin_annotate_locale_en_gb,

        // Because we use the annotate plugin we also need
        // to import the markup editor locale
        markup_editor_locale_en_gb,

        // Import the default properties
        markup_editor_defaults,
        plugin_finetune_defaults,
    } from 'doka.js';

    // This registers the plugins with Doka Image Editor
    setPlugins(plugin_crop, plugin_finetune, plugin_annotate);

    // Merge all the locale objects
    const myLocale = {
        ...locale_en_gb,
        ...plugin_crop_locale_en_gb,
        ...plugin_finetune_locale_en_gb,
        ...plugin_annotate_locale_en_gb,
        ...markup_editor_locale_en_gb,
    };

    // Load the custom element
    const elements = await defineCustomElements();

    elements.forEach((editor) => {
        Object.assign(editor, {
            // Set default imageReader
            imageReader: createDefaultImageReader(),

            // Set Markup Editor defaults
            ...markup_editor_defaults,

            // Set Finetune plugin defaults
            ...plugin_finetune_defaults,

            // Set locale
            locale: myLocale,
        });
    });
</script>

Next steps

With the editor set up, we can continue to configure the editor to our liking with the available instance properties