Preserve input image aspect ratio when sliders are at default

The Qwen-Image-Edit pipeline defaults to 1024x1024 when given height=None
and width=None, which discards the input image's aspect ratio. When the
user hasn't touched the height/width sliders (both still at the slider
minimum of 256), read the dimensions from input image 1 and pass those
to the pipeline instead, snapped to the nearest multiple of 8 and
clamped to the slider's [256, 2048] range.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app.py

@@ -217,8 +217,17 @@ def infer(
         except Exception:
             continue
 
-    if height==256 and width==256:
-        height, width = None, None
+    # If user left the sliders at their default minimum, derive output dimensions
+    # from input image 1 so the result preserves its aspect ratio. Round to the
+    # nearest multiple of 8 (the pipeline's required dimension step) and clamp
+    # to the slider's [256, 2048] range.
+    if height == 256 and width == 256:
+        if pil_images:
+            ref_w, ref_h = pil_images[0].size
+            width = max(256, min(2048, (ref_w // 8) * 8))
+            height = max(256, min(2048, (ref_h // 8) * 8))
+        else:
+            height, width = None, None
     print(f"Calling pipeline with prompt: '{prompt}'")
     print(f"Negative Prompt: '{negative_prompt}'")
     print(f"Seed: {seed}, Steps: {num_inference_steps}, Guidance: {true_guidance_scale}, Size: {width}x{height}")