[REBOL] Re: do %image.png
From: pwoodward:cncdsl at: 14-Nov-2001 17:40
have you checked out the PNG spec? It's pretty clear about how the file is
Basically using a combination of read/part/skip you should be able to
navigate thru the various chunks to get to the chunk you want. The first 4
bytes of a chunk indicate its length, and the next 4 indicate the chunk
type. So - after reading the first 8 bytes of the file to verify it's a
PNG, read the next 8 bytes and take a look at them to see if the next chunk
is a "tEXt" chunk - if not use the length value as the skip in a read...
You'll have to accumulate bytes read and what not though. But - it'd avoid
you having to scan thru the file for an identifier.