Pixlr document format
The pixlr format is a compressed binary format, why we choose this and not a xml/jpg ish format is due to many reasons.
It all comes down to quality, speed and file size.
The pxd file is compressed with zlib to reduce the file size.
The uncompressed data are then ordered into two main sections. The Header and the Layer section.
The header includes, pxd version, color-mode, width, height and number of layers.