如何僅使用 CSS 濾鏡將黑色轉換為任何顏色？

如何僅使用CSS 過濾器將黑色轉換為任何給定的顏色

問題詢問如何產生CSS 過濾器以僅使用CSS 將黑色轉換為給定的目標顏色

方法

一種可能的方法是使用以下公式：

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

這會將黑色轉換為給定的目標顏色。

替代方法

更有效率、更準確的替代方法是使用以下程式碼：

<code class="javascript">class Color {
    constructor(r, g, b) { this.set(r, g, b); }
    toString() { return `rgb(${Math.round(this.r)}, ${Math.round(this.g)}, ${Math.round(this.b)})`; }

    set(r, g, b) {
        this.r = this.clamp(r);
        this.g = this.clamp(g);
        this.b = this.clamp(b);
    }

    hueRotate(angle = 0) {
        angle = angle / 180 * Math.PI;
        let sin = Math.sin(angle);
        let cos = Math.cos(angle);

        this.multiply([
            0.213 + cos * 0.787 - sin * 0.213, 0.715 - cos * 0.715 - sin * 0.715, 0.072 - cos * 0.072 + sin * 0.928,
            0.213 - cos * 0.213 + sin * 0.143, 0.715 + cos * 0.285 + sin * 0.140, 0.072 - cos * 0.072 - sin * 0.283,
            0.213 - cos * 0.213 - sin * 0.787, 0.715 - cos * 0.715 + sin * 0.715, 0.072 + cos * 0.928 + sin * 0.072
        ]);
    }

    grayscale(value = 1) {
        this.multiply([
            0.2126 + 0.7874 * (1 - value), 0.7152 - 0.7152 * (1 - value), 0.0722 - 0.0722 * (1 - value),
            0.2126 - 0.2126 * (1 - value), 0.7152 + 0.2848 * (1 - value), 0.0722 - 0.0722 * (1 - value),
            0.2126 - 0.2126 * (1 - value), 0.7152 - 0.7152 * (1 - value), 0.0722 + 0.9278 * (1 - value)
        ]);
    }

    sepia(value = 1) {
        this.multiply([
            0.393 + 0.607 * (1 - value), 0.769 - 0.769 * (1 - value), 0.189 - 0.189 * (1 - value),
            0.349 - 0.349 * (1 - value), 0.686 + 0.314 * (1 - value), 0.168 - 0.168 * (1 - value),
            0.272 - 0.272 * (1 - value), 0.534 - 0.534 * (1 - value), 0.131 + 0.869 * (1 - value)
        ]);
    }

    saturate(value = 1) {
        this.multiply([
            0.213 + 0.787 * value, 0.715 - 0.715 * value, 0.072 - 0.072 * value,
            0.213 - 0.213 * value, 0.715 + 0.285 * value, 0.072 - 0.072 * value,
            0.213 - 0.213 * value, 0.715 - 0.715 * value, 0.072 + 0.928 * value
        ]);
    }

    multiply(matrix) {
        let newR = this.clamp(this.r * matrix[0] + this.g * matrix[1] + this.b * matrix[2]);
        let newG = this.clamp(this.r * matrix[3] + this.g * matrix[4] + this.b * matrix[5]);
        let newB = this.clamp(this.r * matrix[6] + this.g * matrix[7] + this.b * matrix[8]);
        this.r = newR; this.g = newG; this.b = newB;
    }

    brightness(value = 1) { this.linear(value); }
    contrast(value = 1) { this.linear(value, -(0.5 * value) + 0.5); }

    linear(slope = 1, intercept = 0) {
        this.r = this.clamp(this.r * slope + intercept * 255);
        this.g = this.clamp(this.g * slope + intercept * 255);
        this.b = this.clamp(this.b * slope + intercept * 255);
    }

    invert(value = 1) {
        this.r = this.clamp((value + (this.r / 255) * (1 - 2 * value)) * 255);
        this.g = this.clamp((value + (this.g / 255) * (1 - 2 * value)) * 255);
        this.b = this.clamp((value + (this.b / 255) * (1 - 2 * value)) * 255);
    }

    hsl() { // Code taken from https://stackoverflow.com/a/9493060/2688027, licensed under CC BY-SA.
        let r = this.r / 255;
        let g = this.g / 255;
        let b = this.b / 255;
        let max = Math.max(r, g, b);
        let min = Math.min(r, g, b);
        let h, s, l = (max + min) / 2;

        if(max === min) {
            h = s = 0;
        } else {
            let d = max - min;
            s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
            switch(max) {
                case r: h = (g - b) / d + (g < b ? 6 : 0); break;
                case g: h = (b - r) / d + 2; break;
                case b: h = (r - g) / d + 4; break;
            } h /= 6;
        }

        return {
            h: h * 100,
            s: s * 100,
            l: l * 100
        };
    }

    clamp(value) {
        if(value > 255) { value = 255; }
        else if(value < 0) { value = 0; }
        return value;
    }
}

class Solver {
    constructor(target) {
        this.target = target;
        this.targetHSL = target.hsl();
        this.reusedColor = new Color(0, 0, 0); // Object pool
    }

    solve() {
        let result = this.solveNarrow(this.solveWide());
        return {
            values: result.values,
            loss: result.loss,
            filter: this.css(result.values)
        };
    }

    solveWide() {
        const A = 5;
        const c = 15;
        const a = [60, 180, 18000, 600, 1.2, 1.2];
</code>

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