enhance outcropping with ability to direct contents of new regions

- When outcropping an image you can now add a `--new_prompt` option, to specify
  a new prompt to be used instead of the original one used to generate the image.

- Similarly you can provide a new seed using `--seed` (or `-S`). A seed of zero
  will pick one randomly.

- This PR also fixes the crash that happened when trying to outcrop an image
  that does not contain InvokeAI metadata.

scripts/invoke.py

@@ -282,7 +282,7 @@ def main_loop(gen, opt):
                     filename = f'{prefix}.{use_prefix}.{seed}.png'
                     tm = opt.text_mask[0]
                     th = opt.text_mask[1] if len(opt.text_mask)>1 else 0.5
-                    formatted_dream_prompt = f'!mask {opt.prompt} -tm {tm} {th}'
+                    formatted_dream_prompt = f'!mask {opt.input_file_path} -tm {tm} {th}'
                     path = file_writer.save_image_and_prompt_to_png(
                         image           = image,
                         dream_prompt    = formatted_dream_prompt,
@@ -322,7 +322,7 @@ def main_loop(gen, opt):
                         tool = re.match('postprocess:(\w+)',opt.last_operation).groups()[0]
                         add_postprocessing_to_metadata(
                             opt,
-                            opt.prompt,
+                            opt.input_file_path,
                             filename,
                             tool,
                             formatted_dream_prompt,
@@ -620,10 +620,16 @@ def do_textmask(gen, opt, callback):
     )
 
 def do_postprocess (gen, opt, callback):
-    file_path = opt.prompt     # treat the prompt as the file pathname
+    file_path = opt.prompt      # treat the prompt as the file pathname
+    if opt.new_prompt is not None:
+        opt.prompt = opt.new_prompt
+    else:
+        opt.prompt = None
+        
     if os.path.dirname(file_path) == '': #basename given
         file_path = os.path.join(opt.outdir,file_path)
 
+    opt.input_file_path = file_path
     tool=None
     if opt.facetool_strength > 0:
         tool = opt.facetool
@@ -710,7 +716,7 @@ def prepare_image_metadata(
     elif len(prior_variations) > 0:
         formatted_dream_prompt = opt.dream_prompt_str(seed=first_seed)
     elif operation == 'postprocess':
-        formatted_dream_prompt = '!fix '+opt.dream_prompt_str(seed=seed)
+        formatted_dream_prompt = '!fix '+opt.dream_prompt_str(seed=seed,prompt=opt.input_file_path)
     else:
         formatted_dream_prompt = opt.dream_prompt_str(seed=seed)
     return filename,formatted_dream_prompt