Fix ImageSequenceReference implicit cast (#889)

* Explicitly cast size_t to int before comparison with frame_zero_padding.

Co-authored-by: charles <[email protected]>>

* Fixed a line in the README to be correct for both python 2 and 3.

Co-authored-by: charles <[email protected]>>

Co-authored-by: charles <[email protected]>>

Author: reinecke

README.md

@@ -83,7 +83,7 @@ import opentimelineio as otio
 
 timeline = otio.adapters.read_from_file("foo.aaf")
 for clip in timeline.each_clip():
-  print clip.name, clip.duration()
+  print(clip.name, clip.duration())
 ```
 
 There are more code examples here: https://github.com/PixarAnimationStudios/OpenTimelineIO/tree/master/examples

src/opentimelineio/imageSequenceReference.cpp

@@ -87,7 +87,7 @@ ImageSequenceReference::ImageSequenceReference(std::string const& target_url_bas
         std::string image_num_string = std::to_string(abs(file_image_num));
 
         std::string zero_pad = std::string();
-        if (image_num_string.length() <  _frame_zero_padding) {
+        if (static_cast<int>(image_num_string.length()) <  _frame_zero_padding) {
             zero_pad = std::string(_frame_zero_padding - image_num_string.length(), '0');
         }