官方文檔:
https://www.w3.org/TR/PNG-CRCAppendix.html
CRC32校驗的數據,看原文
A four-byte CRC (Cyclic Redundancy Code) calculated on the preceding bytes in the chunk, including the chunk type field and chunk data fields, but not including the length field. The CRC can be used to check for corruption of the data. The CRC is always present, even for chunks containing no data. See 5.5: Cyclic Redundancy Code algorithm.
難怪把字節寫回去就跪了,crc32校驗碼寫錯了