I couldn't find any decent image manipulation converters that fitted my needs, so I wrote up a simple tool that does just that.
Compile and run the resulting ImBatch.exe
ImBatch.exe <input pattern> commands.xml <output folder>
The commands.xml is a xml file that tells ImBatch what to do with it. This xml will resize the input image.
<batch>
<actions>
<resize width="2048" height="1546" />
<save/>
</actions>
</batch>
This example will do more, though it may not be that useful :)
<batch>
<actions>
<resize width="100" height="100"/>
<gamma red="0.5" green="0.5" blue="1"/>
<bw/>
<invert/>
<colorfilter filter="red"/>
<rotateflip type="Rotate180FlipNone"/>
<changeextension ext="png"/>
<save/>
</actions>
</batch>
Run a single image first(lie img1.png) to test the options, then run a wildcard input(like *.png) to run it for real.