PNG image in base64 encoding

janise · April 18th, 2006, 10:20 AM

Hello!

Could anyone tell me, please, where can I read about how the data is organized in a PNG image in base64 (or is it HEX or something yet else) format?

I don't need anything very advanced, simply to understand how I could generate, for example, a simple image with PHP.

I found PNG specification (http://www.w3.org/TR/PNG/), but I couldn't really find what I was looking for (I hope that I don't need to learn all that before I can understand the basics of how this works...).

I have a (part of) sample code like this (which needs to be base64 encoded and then when output generate a PNG image):

Code:

wD//////////////1QAAAAAAAAAAAAAAAAAACjo////////////////
AP////////////+MAAAAAAAAAAAAAAAAAAAAADj////////////////
8A////////////9BAAAAAAAAAAAAAAAAAAAAAAALD//////////////

And wanted to know (at first) what all those characters mean. What is "AP", "8A", "wD"? What do "/"'s (and "1", "Q", "A" etc.) represent.

Can someone, please, explain this or show where I can read about it?

Thanks!

richard.york · April 20th, 2006, 01:58 PM

Er, are you trying to decode base 64?
http://www.php.net/base64_decode

Regards,
Rich

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janise · April 20th, 2006, 02:12 PM

Thank you for the reply!

Well, I would like to know how PNG image is generated so I could change it. I know the code, for example, which would generate a black '2' (see below), but I want it to appear differently, in a different shape, colours etc.

I just said that base64 is used to generate the image. I'm not sure how it is done and why it is done, I just know that there is this code (I don't know what format it is) which if I encode in base64 and output as png image, a browser will display as an image.

2:

Code:

AP/////////////////////////////////////////////////////
8A/////////////////////////////////////////////////////
wD/////////////////////////////////////////////////////
AP/////////////////okFAkCAAABCBIfNT////////////////////
8A///////////////8hAgAAAAAAAAAAAAAAFTo/////////////////
wD//////////////1QAAAAAAAAAAAAAAAAAACjo////////////////
AP////////////+MAAAAAAAAAAAAAAAAAAAAADj////////////////
8A////////////9BAAAAAAAAAAAAAAAAAAAAAAALD//////////////
wD///////////+gAAAAAAAAAHjs+KwMAAAAAAAAVP//////////////
AP///////////1gAAAAAAABM/////6QAAAAAAAAU///////////////
8A////////////KAAAAAAAALj/////+AAAAAAAAAD//////////////
wD///////////+MfGBMOCAI8P/////wAAAAAAAACP//////////////
AP///////////////////////////5wAAAAAAAAw///////////////
8A///////////////////////////oFAAAAAAAAHz//////////////
wD/////////////////////////6CgAAAAAAAAE3P//////////////
AP///////////////////////9ggAAAAAAAAAHT////////////////
8A//////////////////////+0DAAAAAAAAAA8+P///////////////
wD/////////////////////gAAAAAAAAAAAKOj/////////////////
AP//////////////////9FAAAAAAAAAAADzw///////////////////
8A/////////////////+g4AAAAAAAAAABk/P///////////////////
wD////////////////oKAAAAAAAAAAMqP//////////////////////
AP//////////////6CgAAAAAAAAAMNz////////////////////////
8A//////////////g4AAAAAAAAAFT0/////////////////////////
wD/////////////bAAAAAAAAABU/P//////////////////////////
AP///////////8wAAAAAAAAAAAAAAAAAAAAAAAAA///////////////
8A////////////SAAAAAAAAAAAAAAAAAAAAAAAAAD//////////////
wD//////////9wAAAAAAAAAAAAAAAAAAAAAAAAAAP//////////////
AP//////////hAAAAAAAAAAAAAAAAAAAAAAAAAAA///////////////
8A//////////9AAAAAAAAAAAAAAAAAAAAAAAAAAAD//////////////
wD//////////xAAAAAAAAAAAAAAAAAAAAAAAAAAAP//////////////
AP////////////////////////////////////////////////////8=

richard.york · April 20th, 2006, 02:21 PM

I'm not following along. PHP's image manipulation functions are found in the GD library, and would be the tools you would use to generate a PNG image.

http://www.php.net/image

Regards,
Rich

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Beginning CSS: Cascading Style Sheets For Web Design
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janise · April 20th, 2006, 02:30 PM

Well, this is a way to generate PNG images not using GD library (which I'm not familiar with too).

It is used by phpBB2 image verification and I just wanted to understand how it works so I could adjust it to my needs.

Thanks!