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/