For a specific image to be optimized, the API uses a unique hash value that is based on the image file content. The reason for using a hash value is to be able to uniquely identify the image - even if, for example, the file name changes. To create a value for image_file_hash you can for example use https://emn178.github.io/online-tools/sha1_checksum.html.
The image optimization comes in two packages. Each of the packages are available both as an API and as an add-on service that can be contracted in our content distribution network, which we can put in front of your websites to cache and accelerate them.
To encode image file to base64 to be used in parameter file https://base64.guru/converter/encode/file.
To generate a UUID, check for example https://www.uuidgenerator.net.
Provide the first two characters of the previously used image_file_hash as the hash_prefix and the job_name as the previously used image_file_hash.