Generate an image from the OpenAI service given a prompt and image size.
Requires the OpenAI API key to be stored in a text file named api.key
This example will generate an image named prompt_text_.png with 256 pixels on each side.
generate_image.sh 'prompt text' 256x256
The usefulness of this script is that it provides an easy way of querying the OpenAI API and downloading the resulting file to a human readable filename.