NativeViewer allows to preview OpenCV images stored in variables of the cv::Mat class. A thumbnail image is shown during the debug when a variable is hovered by mouse with CTRL key pressed down. NativeViewer also formats the string displayed in the "Watch" window to express valuable cv::Mat information.
The extension works only for native C++ code in both Win32 and Win64 projects. Only the Visual Studio 2010 and Visual Studio 2012 are supported, this extension is for 2012. Check the quick start guide for details.
Project page on SourceForge.