fixed output image degradation

fixed output image degradation as described at https://github.com/gradio-app/gradio/issues/10394

app.py

@@ -288,6 +288,7 @@ with gr.Blocks(fill_width=True) as demo:
                     output_image = gr.Image(
                         label="Result",
                         type="pil",
+                        format="png",
                         height=450,
                     )