A modified Netlify CMS image widget that allows restricting image dimensions.

Warning: Very hacky and experimental.

As an npm package:

npm install --save netlify-cms-widget-image-dimensions

import { ImageDimensionsControl, ImageDimensionsPreview, ImageDimensionsSchema } from 'netlify-cms-widget-image-dimensions'

CMS.registerWidget('image_dimensions', ImageDimensionsControl, ImageDimensionsPreview, ImageDimensionsSchema)

Via script tag:

<script src="https://unpkg.com/netlify-cms-widget-image-dimensions@^1.0.0"></script>

<script>
  CMS.registerWidget('image_dimensions', ImageDimensionsControl, ImageDimensionsPreview, ImageDimensionsSchema)
</script>

Add to your Netlify CMS configuration:

    fields:
      - { name: <fieldname>, label: <fieldlabel>, widget: image_dimensions }

To set a limit on the minimum width/height of the image, use min_width and min_height. To set the width/height to be an exact value, use exact_width and exact_height. If you configure both min_width and exact_width then min_width will be ignored, and likewise for min_height and exact_height.

To configure the validation/error message (highly recommended), use validation.

    fields:
      - name: <fieldname>
        label: <fieldlabel>
        widget: image_dimensions
        exact_width: 300
        exact_height: 200
        validation: "Image must be 300x200px"