PDFBeads -- Convert Scanned Images to a Single PDF File
PDFBeads is a small utility written in Ruby which takes scanned page images and converts them into a single PDF file. Unlike other PDF creation tools, PDFBeads attempts to implement the approach typically used for DjVu books. Its key feature is separating scanned text (typically black, but indexed images with a small number of colors are also accepted) from halftone pictures. Each type of graphical data is encoded into its own layer with a specific compression method and resolution.