Exclusion Blend Mode Calculator | Color Blending Tool for Designers

What is the Exclusion Blend Mode?

The CSS exclusion blend mode is a fascinating color blending technique that creates unique visual effects. Understanding its underlying logic can help designers use it more effectively.

Why would I want to use this?

When designing a website or application, maintaining a consistent brand identity is crucial.

However, when applying visual effects like the exclusion blend mode to elements such as headers or overlays, the resulting color may deviate from your intended brand color.

Imagine you have a header fixed over a hero block when your page loads. You want the menu to be red, and the hero is blue. However, you want to apply a modern exclusion effect to keep that header readable. For the header to remain red over blue, it actually needs to be pink.

This is where the Mix Blend Mode Calculator comes in handy. By using this tool, you can calculate the closest color that, when blended with the background color using the exclusion effect, will result in your desired brand color.

How it Works

Here's how CSS calculates the exclusion effect:

Result = Background + Blend - (2 * Background * Blend)

This formula is applied to each RGB channel independently, with values normalized between 0 and 1. The exclusion blend mode creates a result that's similar to a difference blend, but with lower contrast.

~~😱 OMFG Why won't this just work~~ Limitations

The Short Version

Not all color combinations are possible with exclusion blending. Some desired colors may be unachievable, especially when working with highly saturated background colors.

The exclusion blend mode can produce unexpected results with very light or very dark colors, as the effect becomes less noticeable at these extremes.

Limitations of the Exclusion Blend Mode Approach

The exclusion blend mode, while useful for creating interesting color effects, has inherent mathematical limitations that prevent it from achieving exact color matches in all scenarios. Understanding these limitations requires a deeper look into the color mathematics involved.

1. Non-linear Color Transformation

The exclusion blend mode applies a non-linear transformation to the color channels. The formula for each channel is:

Result = A + B - (2 * A * B)

Where A is the background color channel value and B is the blend color channel value, both normalized to the range [0, 1].

This non-linearity means that the relationship between input colors and the resulting color is not straightforward, making it challenging to reverse-engineer exact matches for all desired colors.

2. Limited Color Gamut

The exclusion blend mode operates within the confines of the RGB color space, typically with 8 bits per channel. This limits the possible output colors to a discrete set of 16,777,216 colors (256^3). When dealing with floating-point calculations in the normalized [0, 1] range, rounding errors can occur when converting back to 8-bit integer values, further limiting the precision of the results.

3. Color Channel Independence

The exclusion blend mode operates on each color channel independently. This means that achieving a specific color requires finding a solution that simultaneously satisfies the exclusion equation for all three RGB channels. Due to the non-linear nature of the equation, this is not always possible for every desired color.

4. Mathematical Constraints

Let's examine the exclusion blend formula in more detail:

R_result = R_bg + R_blend - (2 * R_bg * R_blend)
                            G_result = G_bg + G_blend - (2 * G_bg * G_blend)
                            B_result = B_bg + B_blend - (2 * B_bg * B_blend)

For each channel, we can rearrange the equation to solve for the blend color:

R_blend = (R_bg - R_result) / (2 * R_bg - 1)

This equation reveals two critical limitations:

When the background color channel value is 0.5 (128 in 8-bit), the denominator becomes zero, making the equation unsolvable.
The solution is only valid when 0 ≤ R_blend ≤ 1. This constraint is not always satisfied for all combinations of background and desired result colors.

5. Extreme Color Values

The exclusion blend mode becomes less effective and more unpredictable at extreme color values:

When the background is black (0, 0, 0), the result will always be equal to the blend color.
When the background is white (1, 1, 1), the result will always be the inverse of the blend color.
When the blend color is middle gray (0.5, 0.5, 0.5), it will always result in the inverse of the background color.

These special cases further limit the range of achievable colors in certain scenarios.

TLDR

Due to these mathematical and practical limitations, it's not always possible to achieve an exact match for every desired color using the exclusion blend mode. The calculator can provide the closest possible approximation within these constraints, but users should be aware that perfect precision is not guaranteed for all color combinations.

How Our Calculator Works

Our JavaScript calculator uses the following method to determine the exclusion color:

Convert hex color inputs to RGB values (0-255).
Normalize RGB values to the range 0-1.
Apply the exclusion formula to each channel.
Convert the result back to the 0-255 range and then to a hex color.