perf(invoke_ai_web_server): encode intermediate result previews as jpeg

For size savings of about 80%, and jpeg encoding is still plenty fast.

Author: keturn

invokeai/backend/invoke_ai_web_server.py

@@ -7,13 +7,15 @@
 import os
 import shutil
 import traceback
+from pathlib import Path
 from threading import Event
 from uuid import uuid4
 
 import eventlet
-from pathlib import Path
+import invokeai.frontend.dist as frontend
 from PIL import Image
 from PIL.Image import Image as ImageType
+from compel.prompt_parser import Blend
 from flask import Flask, redirect, send_from_directory, request, make_response
 from flask_socketio import SocketIO
 from werkzeug.utils import secure_filename
@@ -22,18 +24,15 @@
     get_canvas_generation_mode,
 )
 from invokeai.backend.modules.parameters import parameters_to_command
-import invokeai.frontend.dist as frontend
 from ldm.generate import Generate
 from ldm.invoke.args import Args, APP_ID, APP_VERSION, calculate_init_img_hash
-from ldm.invoke.conditioning import get_tokens_for_prompt_object, get_prompt_structure, split_weighted_subprompts, \
-    get_tokenizer
+from ldm.invoke.conditioning import get_tokens_for_prompt_object, get_prompt_structure, get_tokenizer
 from ldm.invoke.generator.diffusers_pipeline import PipelineIntermediateState
 from ldm.invoke.generator.inpaint import infill_methods
 from ldm.invoke.globals import Globals, global_converted_ckpts_dir
-from ldm.invoke.pngwriter import PngWriter, retrieve_metadata
-from compel.prompt_parser import Blend
 from ldm.invoke.globals import global_models_dir
 from ldm.invoke.merge_diffusers import merge_diffusion_models
+from ldm.invoke.pngwriter import PngWriter, retrieve_metadata
 
 # Loading Arguments
 opt = Args()
@@ -1063,7 +1062,7 @@ def image_progress(sample, step):
                     (width, height) = image.size
                     width *= 8
                     height *= 8
-                    img_base64 = image_to_dataURL(image)
+                    img_base64 = image_to_dataURL(image, image_format="JPEG")
                     self.socketio.emit(
                         "intermediateResult",
                         {
@@ -1724,10 +1723,11 @@ def dataURL_to_image(dataURL: str) -> ImageType:
 """
 
 
-def image_to_dataURL(image: ImageType) -> str:
+def image_to_dataURL(image: ImageType, image_format:str="PNG") -> str:
     buffered = io.BytesIO()
-    image.save(buffered, format="PNG")
-    image_base64 = "data:image/png;base64," + base64.b64encode(
+    image.save(buffered, format=image_format)
+    mime_type = Image.MIME.get(image_format.upper(), "image/" + image_format.lower())
+    image_base64 = f"data:{mime_type};base64," + base64.b64encode(
         buffered.getvalue()
     ).decode("UTF-8")
     return image_base64