sreechand / pngtocss

Read in a gradient from a png file and spit out CSS for it

pngtocss takes in a png file with a gradient in it and spits out the necessary CSS to draw that gradient.

It only works with:

• 24 bit PNGs
• only linear gradients
• horizontal gradients
• vertical gradients
• diagonal gradients
• multi-colour support only for horizontal and vertical

It does not support:

• radial gradients
• angular gradients (except for perfect diagonal)
• more than 2 colours on diagonal gradients
• alpha transparency

Code

See the examples/ directory for all the pngs that I've tested this with. Feel free to submit your own (keep them small).

See the src/ directory for the source code.

It's written in C, and uses libpng and zlib. You'll need both of those to compile it. Also, I wrote it on MacOSX, so I installed the libraries using ports. You may need to play with the Makefile if you're using a different OS. Sorry, I don't have the time to test, but if you submit a pull request, I'll merge it.

License:

BSD Licensed

Copyright:

2011 Philip Tellis -- [email protected] -- http://bluesmoon.info/

Credits:

Everything I know about reading a PNG I got from Chapter 13 of the libpng book: http://www.libpng.org/pub/png/book/chapter13.html

The CSS gradient syntax came from these wonderful sites:

• http://css-tricks.com/css3-gradients/
• http://webdesignerwall.com/tutorials/cross-browser-css-gradient
• http://hacks.mozilla.org/2009/11/css-gradients-firefox-36/
• http://www.tankedup-imaging.com/css_dev/css-gradient.html

History:

Nicole tweeted about the absence of a tool to convert images to gradients:

I realised that I knew neither what CSS gradients were, nor how to read a PNG file, so figured that this was a good opportunity to learn both at once. I decided to write it in C because I hadn't written C code in a very long time.

Patches welcome.

Things I learnt

• The average of two colours will be closer to one than to the other.

Discussion

Talk about pngtocss on the discussion page