fix: More examples

Author: tmathern

examples/README.md

@@ -8,7 +8,9 @@ The `examples/training.py` script demonstrates how to add a "Do Not Train" asser
 
 ### Signing and Verifying Assets
 
-The `examples/sign.py` script shows how to sign an asset with a C2PA manifest and verify it.
+The `examples/sign.py` script shows how to sign an asset with a C2PA manifest and verify it using a callback signer. Callback signers let you define signing logic, eg. where to load keys from.
+
+The `examples/sign_info.py` script shows how to sign an asset with a C2PA manifest and verify it using a "default" signer created with the needed signer information.
 
 ## Running the Examples
 
@@ -21,6 +23,11 @@ Then you can run the examples with the following commands:
 python examples/training.py
 
 # Run the signing and verification example
+# In this example, signing is done with a Signer created using SignerInfo
+python examples/sign_info.py
+
+# Run the signing and verification example
+# In this example, signing is done using a callback signer
 python examples/sign.py
 ```
 

examples/sign.py

@@ -19,6 +19,10 @@
 from cryptography.hazmat.primitives.asymmetric import ec
 from cryptography.hazmat.backends import default_backend
 
+# Note: Builder, Reader, and Signer support being used as context managers
+# (with 'with' statements), but this example shows manual usage which requires
+# explicitly calling the close() function to clean up resources.
+
 fixtures_dir = os.path.join(os.path.dirname(__file__), "../tests/fixtures/")
 output_dir = os.path.join(os.path.dirname(__file__), "../output/")
 
@@ -30,11 +34,6 @@
 version = c2pa.sdk_version()
 print(version)
 
-# Read existing C2PA metadata from the file
-print("\nReading existing C2PA metadata:")
-with open(fixtures_dir + "C.jpg", "rb") as file:
-    reader = c2pa.Reader("image/jpeg", file)
-    print(reader.json())
 
 # Load certificates and private key (here from the test fixtures)
 # This is OK for development, but in production you should use a
@@ -85,6 +84,7 @@ def callback_signer_es256(data: bytes) -> bytes:
                         "action": "c2pa.created",
                         "parameters": {
                             # could hold additional information about this step
+                            # eg. model used, etc.
                         }
                     }
                 ]
@@ -100,19 +100,21 @@ def callback_signer_es256(data: bytes) -> bytes:
 # which will use the callback signer
 print("\nSigning the image file...")
 builder.sign_file(
-    source_path=fixtures_dir + "C.jpg",
-    dest_path=output_dir + "C_signed.jpg",
+    source_path=fixtures_dir + "A.jpg",
+    dest_path=output_dir + "A_signed.jpg",
     signer=signer
 )
 
-# Clean up the signer
+# Clean up
 signer.close()
+builder.close()
 
-# Read the signed image to verify
+# Re-Read the signed image to verify
 print("\nReading signed image metadata:")
-with open(output_dir + "C_signed.jpg", "rb") as file:
+with open(output_dir + "A_signed.jpg", "rb") as file:
     reader = c2pa.Reader("image/jpeg", file)
     print(reader.json())
+    reader.close()
 
 print("\nExample completed successfully!")
 

examples/sign_using_signer_info.py examples/sign_info.pyexamples/sign_using_signer_info.py renamed to examples/sign_info.py

@@ -19,6 +19,10 @@
 fixtures_dir = os.path.join(os.path.dirname(__file__), "../tests/fixtures/")
 output_dir = os.path.join(os.path.dirname(__file__), "../output/")
 
+# Note: Builder, Reader, and Signer support being used as context managers
+# (with 'with' statements), but this example shows manual usage which requires
+# explicitly calling the close() function to clean up resources.
+
 # Ensure the output directory exists
 if not os.path.exists(output_dir):
     os.makedirs(output_dir)
@@ -32,18 +36,21 @@
 with open(fixtures_dir + "C.jpg", "rb") as file:
     reader = c2pa.Reader("image/jpeg", file)
     print(reader.json())
+    reader.close()
 
 # Create a signer from certificate and key files
 certs = open(fixtures_dir + "es256_certs.pem", "rb").read()
 key = open(fixtures_dir + "es256_private.key", "rb").read()
 
+# Define Signer information
 signer_info = c2pa.C2paSignerInfo(
     alg=b"es256",  # Use bytes instead of encoded string
     sign_cert=certs,
     private_key=key,
     ta_url=b"http://timestamp.digicert.com"  # Use bytes and add timestamp URL
 )
 
+# Create the Signer from the information
 signer = c2pa.Signer.from_info(signer_info)
 
 # Create a manifest definition as a dictionary
@@ -74,6 +81,7 @@
     ]
 }
 
+# Create the builder with the manifest definition
 builder = c2pa.Builder(manifest_definition)
 
 # Sign the image
@@ -87,6 +95,11 @@
 with open(output_dir + "C_signed.jpg", "rb") as file:
     reader = c2pa.Reader("image/jpeg", file)
     print(reader.json())
+    reader.close()
+
+# Clean up resources manually, since we are not using with statements
+signer.close()
+builder.close()
 
 print("\nExample completed successfully!")