Page 2 - Algorithms Forum?

There should be a forum for regular expressions containing one post, and it should read: "Are you absolutely sure you need a regular expression?".

I had the idea of the algorithm forum because of a trouble that I found in my job.

I was developing a system to store logos and ringing tones for mobile phones. The problem came when I was asked to convert to only 2 colors (black and transparent) any image that the user uploaded (in True Color, for example).

Then, searching a lot, I finally found some image dithering techniques which I found very interesting (and useful). And then I thought myself that an algorithms forum would suit for those questions that are not tied to any language.

Note: the function is only 12 lines in C.

I didn't post the question (nor the answer) to any forum because I know that in the PHP forum it would be of no interest to those of "please, give me the result of a query".

It took me to another trouble. Good image resizing. What are bilinear and trilinear filters? And when to use them, before or after the dithering ?

I think most of us have ever had a similar trouble.

It sounds like you should pick up a book on image manipulation. Bear in mind though that 12 lines of code in C can still run extremely slow in PHP. I've mentioned this before, but when I implemented the quicksort algorithm in PHP and compared it's running time to the internal sort() routine (which also uses quicksort), the PHP implementation was in the order of 1000 times slower. Have you had a look at imagemagick? http://www.imagemagick.org/ It's available for PHP I think...