HSB Colors with Sass

Alexander Futekov
Alexander Futekov
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Why do we need another color model you might ask? And it is a fair question, considering we already have RGB, HSL, and hex and we’re doing just fine. To convince you, I will tell you why HSB is awesome and how you can easily implement it in any Sass project.

Why HSB?

The HSB/HSV color model is actually a close kin of HSL. HSB stands for Hue, Saturation, and Brightness, the Hue component being equal to the one in HSL.

HSB colors, just like their cousin HSL, have some nice advantages over RGB and Hex — they allow you to quickly identify a color by seeing how saturated and bright it is, Chris Coyier also tells us why HSL is cooler and Dudley Storey has a nice visual guide on how to think about HSL colors. All of these pros apply equally well to HSB.

In addition, Karen Menezes wrote a helpful article on how to think about color modifications with a great section about the HSL model. HSL even has its own mother-effing site.

This easy-to-understand-at-a-glance factor isn’t present in RGB and hex — just try to imagine what rgb(173, 149, 128) or #ad9580 look like.

Also, if you need some level of transparency for a color, hex is no longer an option; you have to choose between RGBa and HSLa (and now HSBa).

HSB colors are also more readily available for use than HSL if you choose/get your colors from graphics software. Programs such as GIMP or Adobe’s Photoshop and Illustrator all prefer the HSB color model to HSL.

Having that foundation, let’s see how we can use HSB in a Sass project.

Building the Function

Adding support for HSB colors in your project is easy. We will define an HSB function, so that later we can use it just like HSL or RGB colors:

color: hsb(333, 84, 76)

This function will accept 3 or 4 parameters, the fourth one being the alpha channel, which we will set to 1 (fully opaque) by default:

@function hsb($h-hsb, $s-hsb, $b-hsb, $a: 1)

On the inside, the function will convert the HSB color to HSL (it’s the easiest conversion mathematically speaking). Sass will output the color in its Hex equivalent (or RGBa if the color has transparency) no matter the format you provide the input color in. Other preprocessors work the same way.

The Hue component doesn’t need to be converted, since it’s the same for HSB and HSL. To get the other components though, we need some math.

Deriving the Luminosity of the HSL equivalent to our HSB color is done with a simple equation:

$l-hsl: ($b-hsb/2) * (2 - ($s-hsb/100));

And this is how we calculate the HSL Saturation:

$s-hsl: ($b-hsb * $s-hsb) / if($l-hsl < 50, $l-hsl * 2, 200 - $l-hsl * 2);

The if statement is there for the proper behavior of the saturation, which starts to decrease once the lightness of the HSL surpasses 50%. Here is a more detailed explanation.

In the end, we simply return the new value:

@return hsla($h-hsb, $s-hsl, $l-hsl, $a);

Okay, now we have all 3 components: Hue, Saturation, and Luminosity. But our code isn’t flawless yet. Our function will fail if the third parameter (the Brightness, or $b-hsb) is 0 because we cannot divide by zero. Happily for us, having a brightness of 0 in HSB means that the output color will always be black, no matter what the other two parameters are.

Therefor, the best way to resolve this issue is to add a condition to our function that automatically outputs black if the brightness is zero:

@function hsb($h-hsb, $s-hsb, $b-hsb, $a: 1) {
  @if $b-hsb == 0 {
    @return hsla(0, 0, 0, $a)
  } @else {
    $l-hsl: ($b-hsb/2) * (2 - ($s-hsb/100));
    $s-hsl: ($b-hsb * $s-hsb) / if($l-hsl < 50, $l-hsl * 2, 200 - $l-hsl * 2);
    @return hsla($h-hsb, $s-hsl, $l-hsl, $a);
  }
}

And we’re done. Check out the demo that includes some test cases:

See the Pen HSB Color Function with Sass by SitePoint (@SitePoint) on CodePen.

Alternatively, if you prefer the Stylus preprocessor, you don’t have to feel left out.

A Final Note on Precision

Keep in mind that the color picker of Adobe Photoshop (and other graphics software) does some rounding when calculating the equivalent HSB of a certain Hex color. This happens because these different color models allow for different precision for its color components.

An example of the rounding issue is shown in the CodePen above, under .test-precision, where a hex color from Photoshop outputs rounded HSB values, and if you put these rounded values in an HSB to hex converter (for example the one we just built) we might get a slightly different hex color than the original (the difference however, is imperceptible).

If you play around with this awesome color converter you will see that the HSB/HSV equivalent of most hex and RGB colors doesn’t have all its components nicely rounded like we’re used to seeing in Photoshop. This is the tool I’m recommending if you happen to need precise colors or just want to avoid this rounding issue for Zen reasons.

Frequently Asked Questions (FAQs) about HSB Colors with Sass

What is the difference between HSB and HSL color systems?

HSB and HSL are both color models that represent color in a more human-friendly way than the RGB model. HSB stands for Hue, Saturation, and Brightness, while HSL stands for Hue, Saturation, and Lightness. The main difference between the two lies in the third parameter. In HSB, brightness is a measure of how much white or black is mixed with the color, while in HSL, lightness is a measure of how much white or black is mixed with the color, but it also takes into account the saturation of the color.

How can I convert HSB colors to RGB in Sass?

Sass provides a built-in function called adjust-hue that can be used to convert HSB colors to RGB. Here’s an example of how you can use it:
$color: hsb(120, 100%, 50%);
$rgb-color: adjust-hue($color, 180deg);
In this example, adjust-hue function changes the hue of the color by 180 degrees, effectively converting the HSB color to an RGB color.

Can I use HSB colors in CSS?

CSS does not natively support HSB colors. However, you can use a preprocessor like Sass to work with HSB colors and then compile your Sass code into CSS that uses RGB or HSL colors, which are supported by CSS.

How can I adjust the saturation and brightness of an HSB color in Sass?

You can use the adjust-color function in Sass to adjust the saturation and brightness of an HSB color. Here’s an example:
$color: hsb(120, 100%, 50%);
$adjusted-color: adjust-color($color, $saturation: 20%, $lightness: -10%);
In this example, the adjust-color function increases the saturation by 20% and decreases the brightness by 10%.

What is the range of values for Hue, Saturation, and Brightness in HSB?

In the HSB color model, Hue is measured in degrees from 0 to 360, Saturation is measured in percentage from 0% to 100%, and Brightness is also measured in percentage from 0% to 100%.

How does the HSB color model represent colors?

The HSB color model represents colors in a cylindrical coordinate system. Hue is the angle around the color wheel, Saturation is the distance from the center of the wheel (with 0% being gray and 100% being the most colorful), and Brightness is the lightness or darkness of the color (with 0% being black and 100% being the brightest possible color).

Can I use HSB colors in all browsers?

No, HSB colors are not natively supported in CSS, and therefore not supported in all browsers. However, you can use a preprocessor like Sass to convert HSB colors to RGB or HSL colors, which are supported in all modern browsers.

How can I create a color palette using HSB in Sass?

You can create a color palette by defining a base color and then using the adjust-hue function to create different shades of the base color. Here’s an example:
$base-color: hsb(120, 100%, 50%);
$color-palette: adjust-hue($base-color, 10deg), adjust-hue($base-color, 20deg), adjust-hue($base-color, 30deg);
In this example, the adjust-hue function is used to create three different shades of the base color by adjusting the hue by 10, 20, and 30 degrees.

What are the advantages of using HSB over RGB?

The HSB color model is more intuitive and human-friendly than the RGB model. It allows you to think about color in terms of hue, saturation, and brightness, which are more natural ways of describing color than red, green, and blue. This makes it easier to create color palettes and adjust colors.

How can I convert HSL colors to HSB in Sass?

There’s no built-in function in Sass to convert HSL colors to HSB. However, you can create a custom function to do this. The conversion involves some complex math, but there are resources available online that can guide you through the process.