utils: raspberrypi: ctt: json_pretty_print: Fix printer test

The ctt_pretty_print_json.py file supports being run standalone to test
the code. It however suffers from multiple issues:

- The same input file name is hardcoded, and doesn't exist in the
  repository
- The input file name is used instead of JSON data

Fix both issues and make the input file selectable on the command line.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
Tested-by: David Plowman <david.plowman@raspberrypi.com>

utils/raspberrypi/ctt/ctt_pretty_print_json.py

@@ -4,6 +4,8 @@
 #
 # ctt_pretty_print_json.py - camera tuning tool JSON formatter
 
+import sys
+
 
 """
 takes a collapsed json file and makes it more readable
@@ -72,4 +74,10 @@ def pretty_print_json(str_in, output_filename):
 
 
 if __name__ == '__main__':
-    pretty_print_json("../ctt/ref_json/final_imx477.json", "pretty.json")
+    if len(sys.argv) != 2:
+        print("Usage: %s filename" % sys.argv[0])
+        sys.exit(1)
+
+    input_filename = sys.argv[1]
+    with open(input_filename, "r") as fin:
+        pretty_print_json(fin.read(), "pretty.json")