Keep embedded PngInfo metadata

gradio/components.py

@@ -1357,9 +1357,9 @@ def postprocess(self, y: np.ndarray | PIL.Image | str | Path) -> str:
             dtype = "file"
         else:
             raise ValueError("Cannot process this value as an Image")
-        if dtype in ["numpy", "pil"]:
-            if dtype == "pil":
-                y = np.array(y)
+        if dtype == "pil":
+            out_y = processing_utils.encode_pil_to_base64(y)
+        elif dtype == "numpy":
             out_y = processing_utils.encode_array_to_base64(y)
         elif dtype == "file":
             out_y = processing_utils.encode_url_or_file_to_base64(y)
@@ -3262,8 +3262,7 @@ def postprocess(self, y: List[np.ndarray | PIL.Image | str] | None) -> List[str]
             if isinstance(img, np.ndarray):
                 img = processing_utils.encode_array_to_base64(img)
             elif isinstance(img, PIL.Image.Image):
-                img = np.array(img)
-                img = processing_utils.encode_array_to_base64(img)
+                img = processing_utils.encode_pil_to_base64(img)
             elif isinstance(img, str):
                 img = processing_utils.encode_url_or_file_to_base64(img)
             else:

gradio/processing_utils.py

@@ -12,7 +12,7 @@
 import numpy as np
 import requests
 from ffmpy import FFmpeg, FFprobe, FFRuntimeError
-from PIL import Image, ImageOps
+from PIL import Image, ImageOps, PngImagePlugin
 
 from gradio import encryptor
 
@@ -103,6 +103,25 @@ def save_pil_to_file(pil_image, dir=None):
     return file_obj
 
 
+def encode_pil_to_base64(pil_image):
+    with BytesIO() as output_bytes:
+
+        # Copy any text-only metadata
+        use_metadata = False
+        metadata = PngImagePlugin.PngInfo()
+        for key, value in pil_image.info.items():
+            if isinstance(key, str) and isinstance(value, str):
+                metadata.add_text(key, value)
+                use_metadata = True
+
+        pil_image.save(
+            output_bytes, "PNG", pnginfo=(metadata if use_metadata else None)
+        )
+        bytes_data = output_bytes.getvalue()
+    base64_str = str(base64.b64encode(bytes_data), "utf-8")
+    return "data:image/png;base64," + base64_str
+
+
 def encode_array_to_base64(image_array):
     with BytesIO() as output_bytes:
         pil_image = Image.fromarray(_convert(image_array, np.uint8, force_copy=False))

test/test_processing_utils.py

@@ -57,6 +57,23 @@ def test_encode_array_to_base64(self):
         output_base64 = gr.processing_utils.encode_array_to_base64(numpy_data)
         self.assertEqual(output_base64, deepcopy(media_data.ARRAY_TO_BASE64_IMAGE))
 
+    def test_encode_pil_to_base64(self):
+        img = Image.open("gradio/test_data/test_image.png")
+        img = img.convert("RGB")
+        img.info = {}  # Strip metadata
+        output_base64 = gr.processing_utils.encode_pil_to_base64(img)
+        self.assertEqual(output_base64, deepcopy(media_data.ARRAY_TO_BASE64_IMAGE))
+
+    def test_encode_pil_to_base64_keeps_pnginfo(self):
+        input_img = Image.open("gradio/test_data/test_image.png")
+        input_img = input_img.convert("RGB")
+        input_img.info = {"key1": "value1", "key2": "value2"}
+
+        encoded_image = gr.processing_utils.encode_pil_to_base64(input_img)
+        decoded_image = gr.processing_utils.decode_base64_to_image(encoded_image)
+
+        self.assertEqual(decoded_image.info, input_img.info)
+
     def test_resize_and_crop(self):
         img = Image.open("gradio/test_data/test_image.png")
         new_img = gr.processing_utils.resize_and_crop(img, (20, 20))