libpng (Portable Network Graphics) 1.6.45.
libpng is the PNG image format reference implementation. Portable Network Graphics are the most widely used raster image format, patent-free, based on lossless data compression, support indexed/paletted, grayscale, and 24 or 32 bit truecolor images with transparency. It's also an highly extensible container format, with built-in color profiles and representation information, textual meta data, filters, progressive interlacing, and permits animations in the derived APNG or MNG formats.