Welcome back!  In the first two posts in this series, I covered some of the awesome features in CSS precompilers such as SASS and LESS, as well as how to get an initial project setup up and running in ASP.Net MVC 4. In this post, I will cover an actual advanced example of using LESS in a project, and show some of the great productivity features we gain from its usage.

Introduction

In the first post, I mentioned two subjects that I will be using in this example – constants, and color functions.  I’ve always enjoyed using online color scheme utilities such as Adobe Kuler or Color Scheme Designer to come up with a scheme based off of one primary color.  Using these tools, and requesting a complementary scheme you can get a couple of shades of your primary color, and a couple of shades of a complementary/accent color to display.

Because there is no way in regular css to do color operations or store variables, there was no way to accomplish something like defining a primary color, and have a site theme cascade off of that.  However with tools such as LESS, that impossibility becomes a reality!  So, if you haven’t guessed it by now, this post is on the creation of a plugin/module/less file to drop into your project, plugin one color, and have your primary theme cascade from it.  I only went through the trouble of creating a module for getting Complementary colors.  However, it wouldn’t be too much trouble to go through other options such as Triad or Monochromatic to get a module that you could use off of that.

Step 1 – Analysis

I decided to mimic Adobe Kuler’s Complementary theme algorithm as I liked its simplicity and aesthetics.  Color Scheme Designer is great, but I do believe it can give you too many color options, which can lead to chaos and overload.  The first thing I had to check was if the complementary values for the color schemes were actually hues rotated by 180 degrees at all times – they aren’t.  Apparently Adobe applies some variance to the complementary colors to get colors that are actually more aesthetically appealing to users.  So, I opened up Excel and began to plot complementary hues based on rotation in increments of 10:

Long story short, I completed the same calculations for Hue, Saturation, and Lightness.  For Hue, I only had to record the Complementary hue values, however for saturation and lightness, I had to record the values for ALL of the shades. 

Since the functions were too complicated to put into LESS since they aren’t constant/linear, but rather interval functions, I instead opted to extrapolate the HSL values using the trendline function for each major interval, onto intervals of spacing 1.

For example, using the hue extraction, I got the following values:

Saturation and Lightness were much worse, but in the end, I finally had functions for all of the intervals, and then went the route of just grabbing each shades value in intervals of 1. 

Step 2 – Mapping

I declared variable names for each of these sections as something that shouldn’t ever conflict with a variable someone would define in their own file.  After I had each of the values, I extracted the values and put them into files of their own for hue variables, saturation variables, and lightness variables…  Example:

/*HUE CONVERSIONS*/
@clrizr-hue-source-0deg: 133.43;
@clrizr-hue-source-1deg: 135.601;
@clrizr-hue-source-2deg: 137.772;
@clrizr-hue-source-3deg: 139.943;
@clrizr-hue-source-4deg: 142.114;
.../*SATURATION CONVERSIONS*/
@clrizr-saturation-s2SV0px: 0;
@clrizr-saturation-s2SV1px: 0;
@clrizr-saturation-s2SV2px: 0;
@clrizr-saturation-s2SV3px: 0;
@clrizr-saturation-s2SV4px: 0;
.../*LIGHTNESS CONVERSIONS*/
@clrizr-lightness-s2LV0px: 30;
@clrizr-lightness-s2LV1px: 31;
@clrizr-lightness-s2LV2px: 32;
@clrizr-lightness-s2LV3px: 33;
@clrizr-lightness-s2LV4px: 34;
...

In the end, I have 973 lines of mapping/conversion from source HSL to shade HSL for two extra primary shades, and two complementary shades. The last bit of the work was the file to compose each of the shades from these mappings.

Step 3 – Clrizr Mapper

The final step was the hardest to overcome as I was still trying to understand LESS to its fullest extent. 

Imports

As mentioned previously, I had separated the HSL mappings into different files, so the first necessary step is to import those for use into the Clrizr plugin:

@import url("hue.less");
@import url("saturation.less");
@import url("lightness.less");

Extract Component Values For Each Shade

Next, I extracted the necessary information for each shade HSL before shade composition:

@clrizr-input-saturation: 1px+floor(saturation(@clrizr-input))-1;
@clrizr-input-lightness: 1px+floor(lightness(@clrizr-input))-1;
 
@clrizr-complementary-hue: formatstring("clrizr-hue-source-{0}", ceil(hue(@clrizr-input)));
 
@clrizr-primary-2-saturation: formatstring("clrizr-saturation-s2SV{0}",@clrizr-input-saturation);
@clrizr-primary-1-saturation: formatstring("clrizr-saturation-s1SV{0}",@clrizr-input-saturation);
@clrizr-complementary-1-saturation: formatstring("clrizr-saturation-c1SV{0}",@clrizr-input-saturation);
 
@clrizr-primary-2-lightness: formatstring("clrizr-lightness-s2LV{0}",@clrizr-input-lightness);
@clrizr-primary-1-lightness: formatstring("clrizr-lightness-s1LV{0}",@clrizr-input-lightness);
@clrizr-complementary-1-lightness: formatstring("clrizr-lightness-c1LV{0}",@clrizr-input-lightness);

Here, you can see a couple of odd things…  On the first line, I am using operations to add units to the saturation and lightness.  This is due to some limitations in the operations that would give me saturation or lightness in %, which can’t be in a variable name.  So, I use first add 1px to it, which casts the result of the following functions as px instead of %, and then at the end, I remove that pixel. 

You can also see here the formatstring method which is exactly what it sounds like – something like String.Format(string str, params object[] obj).

Get Primary & Complementary Shades

Now that I have components for each of the different shades, I can now compose them into each of their pieces.  For this, I use the @@ operator which will look for a variable with the name specified in a string, and then call that variable:

@clrizr-primary-2: hsl(hue(@clrizr-input), @@clrizr-primary-2-saturation, @@clrizr-primary-2-lightness);
@clrizr-primary-1: hsl(hue(@clrizr-input), @@clrizr-primary-1-saturation, @@clrizr-primary-1-lightness);
@clrizr-primary: @clrizr-input;
@clrizr-complementary-1: hsl(@@clrizr-complementary-hue, @@clrizr-complementary-1-saturation, @@clrizr-complementary-1-lightness);
@clrizr-complementary-2: hsl(@@clrizr-complementary-hue, saturation(@clrizr-input), lightness(@clrizr-input));

That’s is it, for the most part.  These variables now hold the theme for the one input color – @clrizr-input.  However, I have one last addition…

Perceptive Luminance

Well, after I got the colors, I decided I wanted to also get the best font color that would go on top of it.  Black or white depending on light or dark color.  Now I couldn’t just go with checking the lightness, as that is half the story.  You see, the human eye doesn’t see ALL colors equally well but rather has more cells for interpreting green light compared to blue or red.  So, using the ratio, we can calculate the perceptive luminance of each of the shades, and get the font color that best matches it!

@clrizr-perceptive-luminance-ps2: round(1 - ( (0.299 *  red(@clrizr-primary-2)        )    + ( 0.587 * green(@clrizr-primary-2)        )    + (0.114 * blue(@clrizr-primary-2)))/255)*255;
@clrizr-perceptive-luminance-ps1: round(1 - ( (0.299 *  red(@clrizr-primary-1)        )    + ( 0.587 * green(@clrizr-primary-1)        )    + (0.114 * blue(@clrizr-primary-1)))/255)*255;
@clrizr-perceptive-luminance-ps:  round(1 - ( (0.299 *  red(@clrizr-primary)        )    + ( 0.587 * green(@clrizr-primary)        )    + (0.114 * blue(@clrizr-primary)))/255)*255;
@clrizr-perceptive-luminance-pc1: round(1 - ( (0.299 *  red(@clrizr-complementary-1))    + ( 0.587 * green(@clrizr-complementary-1))    + (0.114 * blue(@clrizr-complementary-1)))/255)*255;
@clrizr-perceptive-luminance-pc2: round(1 - ( (0.299 *  red(@clrizr-complementary-2))    + ( 0.587 * green(@clrizr-complementary-2))    + (0.114 * blue(@clrizr-complementary-2)))/255)*255;
 
@clrizr-col-font-on-primary-2: rgb(@clrizr-perceptive-luminance-ps2, @clrizr-perceptive-luminance-ps2, @clrizr-perceptive-luminance-ps2);
@clrizr-col-font-on-primary-1: rgb(@clrizr-perceptive-luminance-ps1, @clrizr-perceptive-luminance-ps1, @clrizr-perceptive-luminance-ps1);
@clrizr-col-font-on-primary: rgb(@clrizr-perceptive-luminance-ps, @clrizr-perceptive-luminance-ps, @clrizr-perceptive-luminance-ps);
@clrizr-col-font-on-complementary-1: rgb(@clrizr-perceptive-luminance-pc1, @clrizr-perceptive-luminance-pc1, @clrizr-perceptive-luminance-pc1);
@clrizr-col-font-on-complementary-2: rgb(@clrizr-perceptive-luminance-pc2, @clrizr-perceptive-luminance-pc2, @clrizr-perceptive-luminance-pc2);

Conclusion

That’s it!  I have posted a project on clrizr.codePlex.com for this, and included a testing page for you to test out how it works.  Feel free to use it in your own project, and if you have any questions, comments or suggestions, please feel free to leave them here as a comment, or on the contact page!