To specify a DPI via XML API, please use the following format. To see the full documentation on Image2Image controls, please view our master API documenation here.
<?xml version="1.0"?> <query> <format> <output>image</output> <size>100x0</size> <image_format>png</image_format> <resize_method>resize</resize_method> <dpi>72</dpi> <destination/> </format> </query>