The Lenna (or Lena) picture is one of the most widely used standard test images used for compression algorithms.'lena' or 'lenna' is a digitized Playboy centerfold, from November 1972. (Lenna is the spelling in Playboy, Lena is the Swedish spelling of the name.) Lena Soderberg (ne Sjööblom)
The Portable Network Graphics (PNG) is a format for storing compressed raster graphics. The compression engine is based on the Deflate method [RFC1951], designed by PKWare and originally used in PKZIP.
a different approach to image optimization, based on how image data is stored in different formats. Let’s start with the JPEG format and a simple technique called the eight-pixel grid.