『 00.01 - PNG : General 』

PNG File Header

大小：8 bytes
內容：0x89 0x50 0x4E 0x47 0x0D 0x0A 0x1A 0x0A

PNG Chunks

• Chunk Length
  4 bytes unsigned integer specifying "Chunk Data" size. Valid value = 0 ~ 2^31-1
• Chunk Type
  4 bytes of uppercase and lowercase ASCII letters.
  Byte 1: Uppercase = Critical, Lowercase = Ancillary.
  Byte 2: Uppercase = Public, Lowercase = Private.
  Byte 3: Reserved, must be uppercase.
  Byte 4: Uppercase = Unsafe to copy, Lowercase = Safe to copy.
• Chunk Data
  Can be zero length.
• Chunk CRC
  4 bytes of CRC calculated on the preceding Chunk Type + Chunk Data.

資料來源

• PNG Specification : 2nd Edition [http://www.w3.org/TR/PNG/]
• PNG - Wikipedia [http://en.wikipedia.org/wiki/PNG]
• PNG Specification: File Structure [http://www.libpng.org/pub/png/spec/1.2/PNG-Structure.html]