add ability to post-process images from the CLI

- supports gfpgan, esrgan, codeformer and embiggen
- To use:
   dream> !fix ./outputs/img-samples/000056.292144555.png -ft gfpgan -U2 -G0.8
   dream> !fix ./outputs/img-samples/000056.292144555.png -ft codeformer -G 0.8
   dream> !fix ./outputs/img-samples/000056.29214455.png  -U4
   dream> !fix ./outputs/img-samples/000056.292144555.png -embiggen 1.5

   The first example invokes gfpgan to fix faces and esrgan to upscale.
   The second example invokes codeformer to fix faces, no upscaling
   The third example uses esrgan to upscale 4X
   The four example runs embiggen to enlarge 1.5X

- This is very preliminary work. There are some anomalies to note:
  1. The syntax is non-obvious. I would prefer something like:
     !fix esrgan,gfpgan
     !fix esrgan
     !fix embiggen,codeformer

     However, this will require refactoring the gfpgan and embiggen
     code.

   2. Images generated using gfpgan, esrgan or codeformer all are named
      "xxxxxx.xxxxxx.postprocessed.png" and the original is saved.
      However, the prefix is a new one that is not related to the
      original.

   3. Images generated using embiggen are named "xxxxx.xxxxxxx.png",
      and once again the prefix is new. I'm not sure whether the
      prefix should be aligned with the original file's prefix or not.
      Probably not, but opinions welcome.

scripts/dream.py

@@ -132,6 +132,8 @@ def main_loop(gen, opt, infile):
         name_max = 255
 
     while not done:
+        operation = 'generate'   # default operation, alternative is 'postprocess'
+        
         try:
             command = get_next_command(infile)
         except EOFError:
@@ -152,8 +154,14 @@ def main_loop(gen, opt, infile):
         if command.startswith(
             '!dream'
         ):   # in case a stored prompt still contains the !dream command
-            command.replace('!dream','',1)
+            command = command.replace('!dream ','',1)
 
+        if command.startswith(
+                '!fix'
+        ):
+            command = command.replace('!fix ','',1)
+            operation = 'postprocess'
+            
         if opt.parse_cmd(command) is None:
             continue
         if len(opt.prompt) == 0:
@@ -166,7 +174,7 @@ def main_loop(gen, opt, infile):
         if not opt.height:
             opt.height = model_config.height
         
-        # retrieve previous value!
+        # retrieve previous value of init image if requested
         if opt.init_img is not None and re.match('^-\\d+$', opt.init_img):
             try:
                 opt.init_img = last_results[int(opt.init_img)][0]
@@ -177,7 +185,8 @@ def main_loop(gen, opt, infile):
                 opt.init_img = None
                 continue
 
-        if opt.seed is not None and opt.seed < 0:   # retrieve previous value!
+        # retrieve previous valueof seed if requested
+        if opt.seed is not None and opt.seed < 0:   
             try:
                 opt.seed = last_results[opt.seed][1]
                 print(f'>> Reusing previous seed {opt.seed}')
@@ -276,12 +285,16 @@ def main_loop(gen, opt, infile):
                         results.append([path, formatted_dream_prompt])
                 last_results.append([path, seed])
 
-            catch_ctrl_c = infile is None # if running interactively, we catch keyboard interrupts
-            gen.prompt2image(
-                image_callback=image_writer,
-                catch_interrupts=catch_ctrl_c,
-                **vars(opt)
-            )
+            if operation == 'generate':
+                catch_ctrl_c = infile is None # if running interactively, we catch keyboard interrupts
+                gen.prompt2image(
+                    image_callback=image_writer,
+                    catch_interrupts=catch_ctrl_c,
+                    **vars(opt)
+                )
+            elif operation == 'postprocess':
+                print(f'>> fixing {opt.prompt}')
+                do_postprocess(gen,opt,image_writer)
 
             if opt.grid and len(grid_images) > 0:
                 grid_img   = make_grid(list(grid_images.values()))
@@ -319,7 +332,27 @@ def main_loop(gen, opt, infile):
 
     print('goodbye!')
 
+def do_postprocess (gen, opt, callback):
+    file_path = opt.prompt     # treat the prompt as the file pathname
+    if os.path.dirname(file_path) == '': #basename given
+        file_path = os.path.join(opt.outdir,file_path)
+    if not os.path.exists(file_path):
+        print(f'* file {file_path} does not exist')
+        return
 
+    tool = opt.facetool if opt.gfpgan_strength > 0 else ('embiggen' if opt.embiggen else 'upscale')
+    opt.save_original = True # do not overwrite old image!
+    return gen.apply_postprocessor(
+        image_path      = opt.prompt,
+        tool            = tool,
+        gfpgan_strength = opt.gfpgan_strength,
+        codeformer_fidelity = opt.codeformer_fidelity,
+        save_original       = opt.save_original,
+        upscale             = opt.upscale,
+        callback            = callback,
+        opt                 = opt,
+        )
+    
 def get_next_command(infile=None) -> str:  # command string
     if infile is None:
         command = input('dream> ')