my goal is to implement a preprocessing step for product image upload. When admin selects an image it should be sent to an external API. The processed image should be uploaded to Shopify.
One approach you could explore would be to use the Admin API to create endpoints for image upload and then create an interface in your app for admins to upload images. On image selection, you would send the image to your external API for processing and once the image is processed, use the Admin API’s MediaImage or Asset resource to upload the processed image to the relevant product in Shopify.