Module memedb_core::png

Portable Network Graphics

PNG data is organized in chunks. Each chunk is structured as follows:

• 4 byte big endian number describing the length of the data within.
• 4 byte ASCII identifier for the chunk type.
• The chunk data itself, which is as long as described in the length field.
• 4 byte CRC-32 checksum of the chunk type and data.

A PNG file starts with a magic number to identify itself, followed by a series of chunks, the first of which must be IHDR, and the last of which must be IEND.

MemeDB stores its tags in a meMe chunk.

Relevant Links

• Wikipedia article for PNG
• The PNG specification
• pngcheck, a program to analyze PNG files

Functions

• read_tags
  Given a src, return the tags contained inside.
• write_tags
  Read data from src, set the provided tags, and write to dest.