Adds a function to decode VP8X chunks

scripts/lsriff.py

@@ -2,7 +2,7 @@
 
 import sys
 
-from yoga.image.encoders.webp import get_riff_structure
+from yoga.image.encoders.webp import get_riff_structure, get_vp8x_info
 
 
 def print_riff_info(input_path):
@@ -20,6 +20,14 @@ def print_riff_info(input_path):
             "        +-- %s [offset: %i, size: %i]"
             % (chunk["type"], chunk["data_offset"], chunk["size"])
         )
+        if chunk["type"] == "VP8X":
+            vp8x_info = get_vp8x_info(
+                image[
+                    chunk["data_offset"] : chunk["data_offset"] + chunk["size"]
+                ]
+            )
+            for key, value in vp8x_info.items():
+                print("            +-- %s: %i" % (key, value))
 
 
 if __name__ == "__main__":

test/test_image_encoders_webp.py

@@ -29,6 +29,70 @@ class Test_get_riff_structure(object):
         assert riff["chunks"][4]["type"] == "XMP "
 
 
+class Test_get_vp8x_info(object):
+    def test_flag_icc(self):
+        vp8x_info = webp.get_vp8x_info(
+            b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+        )
+        assert vp8x_info["has_icc"] is False
+        vp8x_info = webp.get_vp8x_info(
+            b"\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+        )
+        assert vp8x_info["has_icc"] is True
+
+    def test_flag_alpha(self):
+        vp8x_info = webp.get_vp8x_info(
+            b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+        )
+        assert vp8x_info["has_alpha"] is False
+        vp8x_info = webp.get_vp8x_info(
+            b"\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+        )
+        assert vp8x_info["has_alpha"] is True
+
+    def test_flag_exif(self):
+        vp8x_info = webp.get_vp8x_info(
+            b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+        )
+        assert vp8x_info["has_exif"] is False
+        vp8x_info = webp.get_vp8x_info(
+            b"\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+        )
+        assert vp8x_info["has_exif"] is True
+
+    def test_flag_xmp(self):
+        vp8x_info = webp.get_vp8x_info(
+            b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+        )
+        assert vp8x_info["has_xmp"] is False
+        vp8x_info = webp.get_vp8x_info(
+            b"\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+        )
+        assert vp8x_info["has_xmp"] is True
+
+    def test_flag_animation(self):
+        vp8x_info = webp.get_vp8x_info(
+            b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+        )
+        assert vp8x_info["has_anim"] is False
+        vp8x_info = webp.get_vp8x_info(
+            b"\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+        )
+        assert vp8x_info["has_anim"] is True
+
+    def test_canvas_width(self):
+        vp8x_info = webp.get_vp8x_info(
+            b"\x00\x00\x00\x00\xAA\xBB\xCC\x00\x00\x00"
+        )
+        assert vp8x_info["canvas_width"] == 0xCCBBAA + 1
+
+    def test_canvas_height(self):
+        vp8x_info = webp.get_vp8x_info(
+            b"\x00\x00\x00\x00\x00\x00\x00\xAA\xBB\xCC"
+        )
+        assert vp8x_info["canvas_height"] == 0xCCBBAA + 1
+
+
 class Test_encode_lossy_webp(object):
     @pytest.mark.parametrize(
         "image_path",

yoga/image/encoders/webp.py

@@ -35,6 +35,36 @@ def get_riff_structure(data):
     return result
 
 
+def get_vp8x_info(data):
+    # fmt: off
+    #                   RRILEXAR
+    VP8X_FLAG_ICC   = 0b00100000  # noqa: E221
+    VP8X_FLAG_ALPHA = 0b00010000  # noqa: E221
+    VP8X_FLAG_EXIF  = 0b00001000  # noqa: E221
+    VP8X_FLAG_XMP   = 0b00000100  # noqa: E221
+    VP8X_FLAG_ANIM  = 0b00000010  # noqa: E221
+    # fmt: on
+
+    if len(data) != 10:
+        ValueError("Invaild VP8X data")
+
+    return {
+        "has_icc": bool(data[0] & VP8X_FLAG_ICC),
+        "has_alpha": bool(data[0] & VP8X_FLAG_ALPHA),
+        "has_exif": bool(data[0] & VP8X_FLAG_EXIF),
+        "has_xmp": bool(data[0] & VP8X_FLAG_XMP),
+        "has_anim": bool(data[0] & VP8X_FLAG_ANIM),
+        "canvas_width": little_endian_unint32_bytes_to_python_int(
+            data[4:7] + b"\x00"
+        )
+        + 1,
+        "canvas_height": little_endian_unint32_bytes_to_python_int(
+            data[7:10] + b"\x00"
+        )
+        + 1,
+    }
+
+
 def is_riff(file_bytes):
     """Whether or not the given bytes represent a RIFF file.