Convert PBM to CAL

The PBM (Portable Bitmap) file extension, part of the Netpbm project, originated in the late 1980s to facilitate efficient and portable graphics file interchange. Primarily, PBM files are used to store monochrome bitmaps in a simple ASCII text format, ensuring easy compatibility across different systems and platforms. This format supports only black-and-white imagery, making it particularly useful in scenarios where simplicity and minimalism are prioritized, such as in Unix environments for bitmap manipulation and transfer. Its historical significance lies in promoting a standardized approach to bitmap graphics in early computer technology.

The CAL file extension, known as CALS (Continuous Acquisition and Life-cycle Support) Type 1 Image, is a 1-bit black-and-white raster image format developed by the U.S. Department of Defense in the mid-1980s to standardize graphics data interchange for military documentation. It is primarily used for storing and sharing monochrome images while retaining orientation metadata. The format supports both uncompressed and compressed (using CCITT Group 4 compression) images.