Trying to extract pixel values from a given PNG image

Question

Trying to understand PNG format.

Consider this PNG Image:

Answer 1

Just for completeness (eboix's answer is right on the spot)

11- What is the following data?

C6 25 AA 3E 00 00 00 C2

Each chunk ends with a CRC (4 bytes), and starts with 4 bytes that tell its length. So, C6 25 AA 3E is the CRC of the previous chunk (IHDR) and 00 00 00 C2 (194) is the length of the following (IDAT) chunk.

In the same way, the last 4 bytes is the CRC of the IEND chunk.