web-tools on S Anand

Colour spaces

Mon, 27 Aug 2012 14:04:23 +0000

In reality, a colour is a combination of light waves with frequencies between 400-700THz, just like sound is a combination of sound waves with frequencies from 20-20000Hz. Just like mixing various pure notes produces a new sound, mixing various pure colours (like from a rainbow) produces new colours (like white, which isn’t on the rainbow.)

Our eyes aren’t like our ears, though. They have 3 sensors that are triggered differently by different frequencies. The sensors roughly peak around red, green and blue. Roughly.

It turns out that it’s possible to recreate most (not all) colours using a combination of just red, green and blue by mimicking these three sensors to the right level. That’s why TVs and monitors have red, blue and green cells, and we represent colours using hex triplets for RRGGBB – like #00ff00 (green).

There are a number of problems with this from a computational perspective. Conceptually, we think of (R, G, B) as a 3-dimensional cube. That’d mean that 100% red is about as bright as 100% green or blue. Unfortunately, green is a lot brighter than red, which is a lot brighter than blue. Our 3 sensors are not equally sensitive.

You’d also think that a colour that’s numerically mid-way between 2 colours should appear to be mid-way. Far from it.

This means that if you’re picking colours using the RGB model, you’re using something very far from the intuitive human way of perceiving colours.

Which is all very nice, but I’m usually in a rush. So what do I do?

I go to the Microsoft Office colour themes and use a colour picker to pick one. (I extracted them to make life easier.) These are generally good on the eye.
Failing that, I pick something from http://kuler.adobe.com/
Or I go to http://colorbrewer2.org/ and pick a set of colours
If I absolutely have to do things programmatically, I use the HCL colour scheme. The good part is it’s perceptually uniform. The bad part is: not every interpolation is a valid colour.

Comments

isomorphismes 13 Mar 2013 5:20 pm: What colours can’t be created by convex combinations of {R, G, B}? I mean within the visible spectrum.

Markdress

Sat, 03 Dec 2011 18:05:26 +0000

This year, I’ve converted the bulk of my content into Markdown – a simple way of formatting text files in a way that can be rendered into HTML.

Not out of choice, really. It was the only solution if I wanted to:

Edit files on my iPad / iPhone (I’ve started doing that a lot more recently)
Allow the contents to be viewable as HTML as well as text, and
Allow non techies to edit the file

As a bonus, it’s already the format Github and Bitbucket use for markup.

If you toss Dropbox into the mix, there’s a powerful solution there. You can share files via Dropbox as Markdown, and publish them as web pages. There are already a number of solutions that let you do this. DropPages.com and Pancake.io let you share Dropbox files as web pages. Calepin.co lets you blog using Dropbox.

My needs were a bit simpler, however. I sometimes publish Markdown files on Dropbox that I want to see in a formatted way – without having to create an account. Just to test things, or share temporarily.

Enter Markdress.org. My project for this morning.

Just add any URL after markdress.org to render it as Markdown. For example, to render the file at http://goo.gl/zTG1q, visit http://markdress.org/goo.gl/zTG1q.

To test it out, create any text file in your Dropbox public folder, get the public link and append it to http://markdress.org/ without the http:// prefix.

Comments

Gee 14 Jan 2012 12:38 am: Great news. And all the best in your new ventures. Meanwhile, I made a simple bookmarklet for you: https://gist.github.com/1609547
Thejesh GN 5 Dec 2011 6:47 am: Check this http://markdoc.org I have been using it locally for sometime. Its cool.
S Anand 4 Dec 2011 12:18 pm: James, your suggestion on following URLs is spot-on! I’ll put this in (one of these days, when I get back to this…)
S Anand 6 Dec 2011 10:10 pm: You need to have an empty line before a list. For example:
Test
This is a list: * one * two * three
Michael Lajlev 5 Dec 2011 2:12 pm: I seem to struggle getting list items to work http://markdress.org/dl.dropbox.com/u/623576/test.md Any idea?
Gee 12 Jan 2012 9:14 pm: Markdress is great. I have it running on my server. I would like to render files in a directory adjacent to, or inside the app folder, instead of entering a URL path each time. I would like to enter just filename.txt and it would default back to (effectively) /markdress/filename.txt I looked over index.php and tried a few things but I can’t get relative files to render. Is this an enhancement you’ve considered? Thanks for the great tool.
S Anand 13 Jan 2012 12:51 am: I personally use this sort of a variant, but havent gotten around to making the same changes on markdress. I will do that over the next few days, once I settle down.
The Bootcamp Blog Begins | JFDI–Innov8 2012 Bootcamp 3 Dec 2011 8:16 pm (pingback): […] kind of people who can whip up something like Markdress in a […]
James Manning 4 Dec 2011 9:08 am: Awesome! Nicely done! Not sure if it’s by design or not, but FWIW the example given seems to show that relative url’s aren’t handled correctly - the bottom of this page: http://daringfireball.net/projects/markdown/index.text has this relative url: [tfmenu]: /graphics/markdown/mt_textformat_menu.png which gets faithfully rendered into: That fails, of course, with the attempted get operation returning: http://markdress.org/graphics/markdown/mt_textformat_menu.png Could not fetch http://graphics/markdown/mt_textformat_menu.png FWIW, inserting a base tag in the head seems to work fine, like: However, it would have to be the ‘real’ url in the base - IOW, this doesn’t work: On a related note, IMHO it seems like markdress should handle redirects and ‘pass through’ as a redirect to the markdress version. IOW, looking at this example request from the post: http://markdress.org/goo.gl/zTG1q When markdress requested the page and got back a redirect, instead of following it, it should have instead passed back a redirect to: http://markdress.org/daringfireball.net/projects/markdown/index.text IMHO, that’s a better user experience as it’s more clear what’s getting served up (and it would reflect in the title as well). If/when caching was added (assuming it’s not there now), then you’d want to have the canonical url for targets anyway. :) That behavior isn’t required to fix the relative-url issue, but since you’ll have to know what requests redirect to (the call may be implicitly following it now, so you don’t currently know?), then you’ll have the necessary info to do this piece as well. :) Thanks again for marking markdress! It’s definitely going to be incredibly useful!
Jeff Byrnes 6 Dec 2012 3:14 pm: Markdress appears to have expired, any chance of its return?
S Anand 7 Dec 2012 3:53 am: I didn’t think anyone was using it – so I just let the domain expire. Alternatives are at https://github.com/sanand0/markdress#alternatives. You could also host the code yourself.

Make backgrounds transparent

Wed, 28 Apr 2010 06:57:37 +0000

This is the simplest way that I’ve found to make the background colour of an image transparent.

Download GIMP
Open your image. I’ll pick this one:
Optional: Select Image – Mode – RGB if it’s not RGB.
Select Colors – Colors to Alpha…
Click on the white button next to “From” and select the eye-dropper.
Pick the green colour on the image, and click OK

The anti-aliasing is preserved as well.

Comments

Vinu 28 Apr 2010 11:21 pm: There is a tool in MS Office products (Word, Excel, PowerPoint) to set the transparent color as well, assuming of course that you plan to embed the image in a document…
S Anand 29 Apr 2010 7:19 am: Need to use the image in web pages, mostly. Would this MS Office tool still work?
S Anand 29 Apr 2010 7:20 am: True, Ravi. I need to automate this task, though. Tried ImageMagick at first, but gave up after a while.
Vinu 30 Apr 2010 5:51 pm: Good question. If you use a drag and drop, WYSIWYG web page editor, then perhaps it will translate. I tested it between Powerpoint & Word and it worked. Here’s the location of the control on PowerPoint 2007: on the Picture Tools /Format ribbon> Recolor (in the Adjust group, first from the left) drop down to “Set Transparent Color’. Keyboard accelerator = Alt + J P E S.
Atluri 28 Apr 2010 3:59 pm: This works well only for text and images with strong contrast against their background text as an image is outdated ;) and for images i would use blend->merge->eraser for edges!
Vipul 13 May 2010 5:31 am: Remove background option in MS-PowerPoint 2010 works even better. In love with that feature. :)

15 things with RSS

Thu, 23 Jun 2005 12:00:00 +0000

15 things you can do with RSS – like mix RSS scripts, convert any page to RSS, etc.

Google hacks from BuzzToolBox

Mon, 10 Mar 2003 12:00:00 +0000

Google hacks on BuzzToolBox.com.

Audio blogging tools

Sat, 31 Aug 2002 12:00:00 +0000

Garth is working on audio-blogging tools. Given the amount of poetry I see among bloggers, this might unleash a host of blog-singers.

Convert pictures to ASCII

Thu, 24 Jan 2002 12:00:00 +0000

Convert pictures to ASCII. In colour. Quite impressive.

Picture search

Wed, 12 Dec 2001 12:00:00 +0000

A versatile picture search tool.

Morse code translator

Tue, 11 Dec 2001 12:00:00 +0000

.- - .-.. .- … - a morse code translator.

Google image search

Sat, 07 Jul 2001 12:00:00 +0000

Google has an image search with 150 million images. (While on the topic of Google, try this search on dead.long.live.)

Agentland

Sun, 01 Apr 2001 12:00:00 +0000

Agentland is a portal for online agents – somewhat like Apps.com

Create PDF files online

Tue, 13 Mar 2001 12:00:00 +0000

Adobe lets you create PDF files on the Web without using any software.

Search engine with site preview

Fri, 23 Feb 2001 12:00:00 +0000

Room102 is a search engine that previews websites.

web-tools on S Anand

Colour spaces

Comments

Markdress

Comments

Test

Make backgrounds transparent

Comments

15 things with RSS

Google hacks from BuzzToolBox

Audio blogging tools

Convert pictures to ASCII

Picture search

Morse code translator

Google image search

Agentland

Create PDF files online

Search engine with site preview