Convert XLS (Excel) to PNM

The XLS file extension, short for "Excel Spreadsheet", is a legacy format used by Microsoft Excel for storing spreadsheet data. Introduced with Excel 2.0 in 1987, it was the primary format until the introduction of XLSX in 2007. XLS files contain data organized in rows and columns, supporting formulas, macros, and various formatting options, making them essential for data analysis and financial reporting. Despite being replaced by the more robust and secure XLSX format, XLS files remain widely used in many legacy systems and applications.

The PNM (Portable Anymap) file extension, developed by Jef Poskanzer in the 1980s, stands for Portable Any Map. It is an uncompressed raster graphics format designed for portable image storage and exchange, encompassing three sub-formats: PBM (Portable Bitmap), PGM (Portable Graymap), and PPM (Portable Pixmap). PNM files store image data in plain text or binary format, ensuring easy usage across different platforms and applications. This format is widely supported by various image editing software and is valued for its simplicity and lossless compression.