Bit viewer/editor for peeking at PNG format

[DaveC426913]

I want to parse PNG format files, and I need to understand what they're doing with the bytes. Dropping a PNG into Notebook shows ASCII versions of the bytes. I need a small freeware viewer tool to examine the bits themselves.

Can someone point me at something I could use?

Also, while I am reading up on PNG format, I could use some direction on practical (or prefereably even visual idiot's guide) interpretation of the format (as opposed to theory).

D.

 

[dduardo]

If you want to read a png file then I suggest you use libpng. This library is written in C and gives you a low level interface to png files. Here is the documention:

http://www.libpng.org/pub/png/libpng-1.2.5-manual.html

If you know C, it should be easy to use.

Also, if you want to learn more about the format visit the official png website:

http://www.libpng.org/pub/png/

 

[DaveC426913]

I don't know enough C to do much with it. I'll probably write it in a lang more familiar, like Visual Basic.

 

[dduardo]

Low level reading of a png files requires addressing memory using pointers. You can't do that with VB.

Here is what I found on google groups:

"...no VB code seems to be available to fully decode
PNG (or GIF, or JPG for that matter) to screen. Sure, there's C
source available, but nobody seems to want to port it to VB.
The prime reason is probably that these file formats are *heavily*
compressed, and the number-crunching involved in decoding this stuff
(requiring, by the way, floating point calculations) would simply be
too slow in VB."

 

[DaveC426913]

Really? I thought it formatted the pixels in bytes. i.e. each pixel would show as an ASCII value. I guess I was oversimplifying.

Drat. One more stumbling block in the way of my master plan.

 

[dduardo]

You have to understand that you compressing the file and doing some other tranformations to the data. Therefore you can't just start reading at the beginning of the file and expecting to see pixel information. You first must decompress and transform the file into ram and then you can read the pixels chunks from memory. VB just doesn't have the speed or capbabilities to do this.

 

[chroot]

If all you're looking for is a Windows editor that can show binary files, look at UltraEdit or TextPad:

http://www.ultraedit.com/
http://www.textpad.com/

- Warren

 

[dduardo]

Sure you can look at the binary data, but that won't do you any good unless you can decompress the file.