Create an ARGB struct for C header from a PNG

I need to update a logo bitmap to an updated logo. The existing code uses a C header which is loaded via XChangeProperty. I have looked into imagemagick and the Gimp in order to convert the updated png I have into a suitable header. Gimp even said 'export a C header' (or something like it) but the result did not resemble the existing format. How do I go (preferably on the command-line) from a png to a suitable header file? *Edit:* Expanding the question a little, the (now out of date) logo I would like to replace is [in this file](https://github.com/wch/r-source/blob/trunk/src/modules/X11/rlogo_icon.h) and [gets used here](https://github.com/wch/r-source/blob/trunk/src/modules/X11/devX11.c#L1604-L1609) .