How Can CSS Filters Transform Black into Any Given Color?

How to transform black into a given color using CSS filters:

Introduction

This question explores a method to transform the color black (#000) into a specified target color using only CSS filters. The context for this arises from the need to recolor SVGs within a background image, particularly to address certain TeX math features in KaTeX.

Method

The proposed method leverages CSS filters to achieve the color transformation. The specific CSS filters utilized are:

• invert(): Controls the inversion of colors.
• sepia(): Adds a sepia effect.
• saturate(): Adjusts the saturation level.
• hue-rotate(): Rotates the hue value.
• brightness(): Modifies the brightness.
• contrast(): Alters the contrast.

Implementation

The implementation of the CSS filter transformation is as follows:

filter: invert(100%) sepia() saturate(10000%) hue-rotate(0deg) brightness() contrast();

This filter string applies the following operations:

1. Inverts the color to white.
2. Applies a sepia effect.
3. Saturates the color to its maximum level.
4. Rotates the hue to the desired value.
5. Modifies the brightness and contrast as needed.

Considerations

1. CSS filters are not consistently supported across all browsers.
2. Non-black colors may also be affected by the filter operations.
3. Only hue-rotate, brightness, and contrast filters support percentage values; all other filters use fixed parameters.

Performance Enhancement

A faster implementation of this method was developed to improve performance, running approximately 10 times faster than the original approach. The new method is implemented in JavaScript, leveraging the SPSA optimization algorithm.

Example

To transform black (#000) into yellow (#ffff00), the following filter string can be used:

filter: invert(100%) sepia() saturate(10000%) hue-rotate(0deg) brightness(100%) contrast(100%);

Conclusion

This method provides a reliable way to transform black into a specified target color using only CSS filters. The optimized implementation ensures a faster and more accurate conversion.

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