libxlsxwriter is a C library that can be used to write text, numbers, formulas
and hyperlinks to multiple worksheets in an Excel 2007+ XLSX file. It supports
features such as:

* 100% compatible Excel XLSX files.
* Full Excel formatting.
* Merged cells.
* Defined names.
* Autofilters.
* Charts.
* Worksheet PNG/JPEG images.
* Memory optimization mode for writing large files.
* Source code available on GitHub.
* FreeBSD License.
* ANSI C.
* Compiles for 32 and 64 bit.
* The only dependency is on zlib.

WWW: http://libxlsxwriter.github.io/