Hello everyone, I'm totally new to this list, so please pardon me if it's the wrong place to discuss my idea and please point me to a more suitable list. Today, while reading my morning load of news I've come across a Wikipedia article[1] with some embedded LaTeX formulae, used within a table. The table header on that page has background of a distinct color which makes formula images look ugly. Sorry, the article is in Russian and I didn't find an English counterpart to demonstrate the issue, but by looking at the table you should get the idea. My first thought was "What if we could eliminate that white background in favor of alpha channel?" Then it will look equally well no matter what background it is put. As I have some experience with PNG images and alpha channel stuff, I've wrote this simple half-page program (attached) in C++ to transform any grayscale PNG image containing black-on-white text to image with alpha channel added, so it display nicely on any background (except black :). The program uses PNG++, a C++ wrapper library[2] around libpng. A mockup of what it'll look like if we replace currently used formula image in the table header, with an image transformed by my program is attached as well. I think that visual improvement is immediately obvious. Now, thanks for your patience if you read till here. :) I'd like to know if there any drawbacks[3] to the proposed approach? Was it by design that white background is preserved, if so why and can this be refined somehow? -- Regards, Alex [1] http://ru.wikipedia.org/wiki/%D0%9D%D0%B5%D0%B9%D1%82%D1%80%D0%BE%D0%BD%D0%… Note: scroll down one page to see the table [2] http://www.nongnu.org/pngpp/ [3] It needs to be tested with IE6, as it is well known for problems with transparent PNGs.

wrote:

wrote:

Yes, but my understanding is that they perform poorly.

As far as I know, the only thing actually blocking us from doing this was something like IE5 on Mac printing transparent images with black backgrounds. That's probably not relevant anymore.

On Tue, Nov 17, 2009 at 1:05 PM, Brad Jorsch <b-jorsch(a)northwestern.edu> wrote: It's unlikely we'd do that, so you have a good point.

Yeah, I see the whole image-based approach can be really problematic. Have anyone considered using jsMath instead?  At least they claim compatibility with really wide range of browsers/versions: http://www.math.union.edu/~dpvc/jsMath/browsers.html

I agree. I'm willing to contribute some C or C++ code to do the low level stuff of changing colors in the image. How do I proceed?

I agree.  I'm willing to contribute some C or C++ code to do the low level stuff of changing colors in the image.  How do I proceed?

And how comes we can't post-process resulting PNG images with a program written in a different language? :)

So, there can be no way to provide non-alpha transparent image to satisfy all possible styles.

I think we cannot do something sensible now, so we'll just have to wait for MathML support from most popular browsers.

We really don't want to increase the amount of non-PHP code in core unless absolutely necessary, IMO. PHP is an awful language, but it's the only thing that all current MediaWiki developers know. Anything else is much harder to maintain, because only some subset of people with commit access can competently alter it. I'm sure most committers know basic C syntax, but few would be confident enough to make significant changes to a C program (and if they tried they'd probably introduce giant memory leaks and such). Just a while ago, it took days to fix a simple XSS in Timeline because it was written in Perl. Besides, there's no need to reinvent the wheel. dvipng (which is apparently used here) should be able to do whatever we want, as far as I can tell. Failing that, ImageMagick or such would likely do the trick.

If we want to skip transparency and just allow changing the background to any other solid color, it looks like it's pretty easy for a bare-bones fix: just add this as line 736 (in r59357) of texutil.ml:    | "\\pagecolor"        -> (tex_use_color (); LITERAL (TEX_ONLY "\\pagecolor")) Then people can use the "\pagecolor{...}" command to change the background just as they can use "\color{...}" now to change the foreground color (see [[m:Help:Math#Color]]).

Aryeh Gregor <Simetrical+wikilist <at> gmail.com> writes: You could use PNG8 with a color palette where every color is black, with a variable level of transparency. That would be equivalent to full PNG32 alpha transparency in modern browsers (as long as the only color used in the formulas is black), while IE5.5/6 would have binary transparency without any aliasing - ugly but probably not horrible. (See http://www.v-methods.com/ji/palette_alpha.html for a demonstration.)

Or you could just send different images to IE6, for example by using empty divs with background images instead of img tags, and changing the image URL for IE6 with the star-html CSS hack. (Not very accessible, but maybe the text of the formula could be written into the div with overflow:hidden?)

I've whitelisted \definecolor and \pagecolor in r59550.  I'm resolving bug 8 as LATER, and suggest it only be reopened when either IE6 reaches <1% market share, or it can be demonstrated that we can do transparency without significantly hurting IE6 users' experience when reading math articles.

Who cares about that browser??

as long as a IE6 user is still able to read the text, it's ok IMO.

So what?

Sometimes this is necessary though. Many people today still don't know that IE6 is dangerous. Wikipedia should warn those users and tell them how to upgrade.

Aryeh Gregor writes: You could use PNG8 with a color palette where every color is black, with a variable level of transparency. That would be equivalent to full PNG32 alpha transparency in modern browsers (as long as the only color used in the formulas is black), while IE5.5/6 would have binary transparency without any aliasing - ugly but probably not horrible. (See http://www.v-methods.com/ji/palette_alpha.html for a demonstration.)

In practice, rumor suggests that the large majority of IE6 installations are on corporate sites, where IT is unwilling to spend the money testing and deploying a major change when things work well enough already. IE7 breaks a lot of sites that were coded to work only in IE6, particularly corporate intranet sites that ignored compatibility because they knew everyone would only run IE6 (since IT required it).

Havent read the whole thread, but why not just do it the ol' school way. Have texvc create two images one with alpha and the other without, and then serve formula images depending on the user-agent.

Hey, don't get me wrong ... the current state works for me 100%, even if wiki uses non-white background, i'm just throwing ideas here (and i do realize it was a weak idea). IMO these kind of tweaks should be in form of a cofigurable option so people who want to use it and who think it won't screw up their system, could use it. We should have an option to use alpha in PNG for math if you think your wiki can exist without <IE6 compliance. I'm NOT saying this should be used on WMF sites ... in fact i'm AGAINST that. As much as it pains me to say this, all IE browsers still in frequent use (if you can in fact call them browsers) should be supported. That's all