How to darken a given color (int)

问题:

I have a function that takes a given color and I would like it to darken the color (reduce its brightness by 20% or so). I can't figure out how to do this given just a color (int). What is the proper approach?

public static int returnDarkerColor(int color){
    int darkerColor = .... 
    return darkerColor;
}

回答1:

A more Android way of doing it:

    public static int manipulateColor(int color, float factor) {
        int a = Color.alpha(color);
        int r = Math.round(Color.red(color) * factor);
        int g = Math.round(Color.green(color) * factor);
        int b = Math.round(Color.blue(color) * factor);
        return Color.argb(a,
                Math.min(r,255),
                Math.min(g,255),
                Math.min(b,255));
    }

You will want to use a factor less than 1.0f to darken. try 0.8f.

回答2:

There's even a simpler solution that has not been mentioned before, Android has a class called ColorUtils which can you help you with that here's a Kotlin snippet of an extension function

inline val @receiver:ColorInt Int.darken
    @ColorInt
    get() = ColorUtils.blendARGB(this, Color.BLACK, 0.2f)

the method ColorUtils.blendARGB takes your color as the first parameter and the second color you want to blend, black in this case and finally, the last parameter is the ratio between your color and the black color you're blending.

回答3:

A simpler solution using HSV like RogueBaneling suggested:

Kotlin

@ColorInt fun darkenColor(@ColorInt color: Int): Int {
    return Color.HSVToColor(FloatArray(3).apply {
        Color.colorToHSV(color, this)
        this[2] *= 0.8f
    })
}

Java

@ColorInt int darkenColor(@ColorInt int color) {
    float[] hsv = new float[3];
    Color.colorToHSV(color, hsv);
    hsv[2] *= 0.8f;
    return Color.HSVToColor(hsv);
}

No complex bitwise operations or Math necessary. Move 0.8f to an argument if needed.

回答4:

If you want more simple and not accurately, below might help you.

public static int returnDarkerColor(int color){
    float ratio = 1.0f - 0.2f;
    int a = (color >> 24) & 0xFF;
    int r = (int) (((color >> 16) & 0xFF) * ratio);
    int g = (int) (((color >> 8) & 0xFF) * ratio);
    int b = (int) ((color & 0xFF) * ratio);

    return (a << 24) | (r << 16) | (g << 8) | b;
}

回答5:

Convert the color to a HSV array, then reduce the brightness by 20%, then convert HSV array back to RGB with HSVToColor. Note: The value you are looking to change in the array will be the V-value. (i.e., hsv[2])

回答6:

This way you can select percentage of color and thus fetch a shade darker or a shade lighter

`    int color = ((ColorDrawable)c2.getBackground()).getColor();
            int  colorLighter=-color*40/100+color;
            int  colorDarker=+color*40/100+color;    `

colorlighter gives us a lighter shade of color from button's background colordarker gives us a darker shade of color from button's background