unprompted/docs/shortcodes/init_image.md

Gets or sets image from the given path as the initial image for use with img2img. Call this without any arguments to get the current image.

Note that path must be an absolute path, including the file extension.

If the given path ends with the * wildcard, [init_image] will choose a random file in that directory.

Important: At the moment, you still have to select an image in the WebUI before pressing Generate, or this shortcode will throw an error. You can select any image - it doesn't matter what it is, just as long as the field isn't empty.

[init_image "C:/pictures/my_image.png"]