When developing for/with OpenCV using Visual Studio, the Image Watch plug-in is very useful. However, it does not support the better-typed cv::Matx types (e.g. cv::Matx33f which is the same as cv::Matx<float,3,3> ). Here is how I made use of Visual Studio’s debugger type visualizers to customize the plugin:

1. Go to the folder <VS Installation Directory>\Common7\Packages\Debugger\Visualizers\ and create a new file called Matx.natvis
2. Open the file and insert the following:

   <?xml version="1.0" encoding="utf-8"?>
   <!-- Philipp Hasper, http://www.hasper.info-->
   <AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
   <UIVisualizer ServiceId="{A452AFEA-3DF6-46BB-9177-C0B08F318025}" Id="1" MenuName="Add to Image Watch"/>
   
   <Type Name="cv::Matx<*,*,*>">
   <UIVisualizer ServiceId="{A452AFEA-3DF6-46BB-9177-C0B08F318025}" Id="1" />
   </Type>
   
   <Type Name="cv::Matx<*,*,*>">
   <DisplayString Condition='strcmp("float", "$T1") == 0'>{{FLOAT32, size = {$T3}x{$T2}}}</DisplayString>
   <DisplayString Condition='strcmp("double", "$T1") == 0'>{{FLOAT64, size = {$T3}x{$T2}}}</DisplayString>
   
   <Expand>
   <Synthetic Name="[type]" Condition='strcmp("float", "$T1") == 0'>
   <DisplayString>FLOAT32</DisplayString>
   </Synthetic>
   <Synthetic Name="[type]" Condition='strcmp("double", "$T1") == 0'>
   <DisplayString>FLOAT64</DisplayString>
   </Synthetic>
   
   <Item Name="[channels]">1</Item>
   <Item Name="[width]">$T3</Item>
   <Item Name="[height]">$T2</Item>
   <Item Name="[data]">(void*)val</Item>
   <Item Name="[stride]">$T3*sizeof($T1)</Item>
   </Expand>
   
   </Type>
   
   </AutoVisualizer>

3. You do not even have to restart Visual Studio. Just start a new debugging session and you can look at your cv::Matx types in a nice little graphical window.

More about customizing the Image Watch plug-in can be found on the official Image Watch documentation page.