docs: Add example read.py script (#207)

* Expose `load_settings()` and `version()` for import to allow specifying custom settings (like a certificate trust list).

* Add an example read.py script to show how to read a file's C2PA manifest and verify it.

* Address PR comments

* Remove __init__.py changes

Author: Res260

README.md

@@ -34,6 +34,7 @@ import c2pa
 
 See the [`examples` directory](https://github.com/contentauth/c2pa-python/tree/main/examples) for some helpful examples:
 
+- `examples/read.py` shows how to read and verify an asset with a C2PA manifest.
 - `examples/sign.py` shows how to sign and verify an asset with a C2PA manifest.
 - `examples/training.py` demonstrates how to add a "Do Not Train" assertion to an asset and verify it.
 

examples/README.md

@@ -75,7 +75,13 @@ except Exception as err:
 
 To run the examples, make sure you have the c2pa-python package installed (`pip install c2pa-python`) and you're in the root directory of the project. We recommend working using virtual environments (venv). Then run the examples as shown below.
 
-Run the "do not train" assertion example:
+### Run the reading C2PA data example
+
+```bash
+python examples/read.py
+```
+
+### Run the "do not train" assertion example:
 
 ```bash
 python examples/training.py

examples/read.py

@@ -0,0 +1,47 @@
+import sys
+import c2pa
+import urllib.request
+
+
+# This example shows how to read a C2PA manifest embedded in a media file, and validate
+# that it is trusted according to the official trust anchor certificate list.
+# The output is printed as prettified JSON.
+
+TRUST_ANCHORS_URL = "https://contentcredentials.org/trust/anchors.pem"
+
+
+def load_trust_anchors():
+    try:
+        with urllib.request.urlopen(TRUST_ANCHORS_URL) as response:
+            anchors = response.read().decode('utf-8')
+        settings = {
+            "verify": {
+                "verify_cert_anchors": True
+            },
+            "trust": {
+                "trust_anchors": anchors
+            }
+        }
+        c2pa.load_settings(settings)
+    except Exception as e:
+        print(f"Warning: Could not load trust anchors from {TRUST_ANCHORS_URL}: {e}")
+
+
+def read_c2pa_data(media_path: str):
+    print(f"Reading {media_path}")
+    try:
+        with c2pa.Reader(media_path) as reader:
+            print(reader.detailed_json())
+    except Exception as e:
+        print(f"Error reading C2PA data from {media_path}: {e}")
+        sys.exit(1)
+
+
+if __name__ == '__main__':
+    if len(sys.argv) < 2:
+        media_path = "tests/fixtures/cloud.jpg"
+    else:
+        media_path = sys.argv[1]
+
+    load_trust_anchors()
+    read_c2pa_data(media_path)