Dynamically Change Color to Lighter or Darker by Percentage Css

Dynamically change color to lighter or darker by percentage CSS

All modern browsers have had 100% filter support since January 2020. Even UC Browser for Android (instead of Chrome, on the $80 phones) supports it.

a {
    /* a nice, modern blue for links */
    color: #118bee;
}
a:active {
    /* Darken on click by 15% (down to 85%) */
    filter: brightness(0.85);
}

Additionally, you can control this dynamically with CSS variables, which have been supported by most browsers since October 2017 (excluding QQ):

:root {
    --color: #118bee;
    --hover-brightness: 1.2;
}
a {
    color: var(--color);
}
a:active {
    /* Darken on click */
    filter: brightness(var(--hover-brightness));
}

Not my project, but one that's great to look at for a real-world example of how great modern CSS can be, check out: MVP.css

Original Answer

If you're using a stack which lets you use Sass or Less, you can use the lighten function:

$linkcolour: #0000FF;

a {
  color: $linkcolour;
}

a.lighter {
  color: lighten($linkcolour, 50%);
}

There's also darken which does the same, but in the opposite direction.

Make background-color darker dynamically without making text color darker

After trying different methods I came up with this solution using box-shadow.

box-shadow: -200px -200px 0px 200px rgb(0 0 0 / 10%) inset
/* This is an inset `box-shadow` and will not affect the color of the text. */

Cross platform solution:

box-shadow: -200px -200px 0px 200px rgba(0,0,0,0.10) inset;
-webkit-box-shadow: -200px -200px 0px 200px rgba(0,0,0,0.10) inset;
-moz-box-shadow: -200px -200px 0px 200px rgba(0,0,0,0.10) inset;

How to generate a CSS color that is some specific percentage lighter/darker using JavaScript

var pad = function(num, totalChars) {
    var pad = '0';
    num = num + '';
    while (num.length < totalChars) {
        num = pad + num;
    }
    return num;
};

// Ratio is between 0 and 1
var changeColor = function(color, ratio, darker) {
    // Trim trailing/leading whitespace
    color = color.replace(/^\s*|\s*$/, '');

    // Expand three-digit hex
    color = color.replace(
        /^#?([a-f0-9])([a-f0-9])([a-f0-9])$/i,
        '#$1$1$2$2$3$3'
    );

    // Calculate ratio
    var difference = Math.round(ratio * 256) * (darker ? -1 : 1),
        // Determine if input is RGB(A)
        rgb = color.match(new RegExp('^rgba?\\(\\s*' +
            '(\\d|[1-9]\\d|1\\d{2}|2[0-4][0-9]|25[0-5])' +
            '\\s*,\\s*' +
            '(\\d|[1-9]\\d|1\\d{2}|2[0-4][0-9]|25[0-5])' +
            '\\s*,\\s*' +
            '(\\d|[1-9]\\d|1\\d{2}|2[0-4][0-9]|25[0-5])' +
            '(?:\\s*,\\s*' +
            '(0|1|0?\\.\\d+))?' +
            '\\s*\\)$'
        , 'i')),
        alpha = !!rgb && rgb[4] != null ? rgb[4] : null,

        // Convert hex to decimal
        decimal = !!rgb? [rgb[1], rgb[2], rgb[3]] : color.replace(
            /^#?([a-f0-9][a-f0-9])([a-f0-9][a-f0-9])([a-f0-9][a-f0-9])/i,
            function() {
                return parseInt(arguments[1], 16) + ',' +
                    parseInt(arguments[2], 16) + ',' +
                    parseInt(arguments[3], 16);
            }
        ).split(/,/),
        returnValue;

    // Return RGB(A)
    return !!rgb ?
        'rgb' + (alpha !== null ? 'a' : '') + '(' +
            Math[darker ? 'max' : 'min'](
                parseInt(decimal[0], 10) + difference, darker ? 0 : 255
            ) + ', ' +
            Math[darker ? 'max' : 'min'](
                parseInt(decimal[1], 10) + difference, darker ? 0 : 255
            ) + ', ' +
            Math[darker ? 'max' : 'min'](
                parseInt(decimal[2], 10) + difference, darker ? 0 : 255
            ) +
            (alpha !== null ? ', ' + alpha : '') +
            ')' :
        // Return hex
        [
            '#',
            pad(Math[darker ? 'max' : 'min'](
                parseInt(decimal[0], 10) + difference, darker ? 0 : 255
            ).toString(16), 2),
            pad(Math[darker ? 'max' : 'min'](
                parseInt(decimal[1], 10) + difference, darker ? 0 : 255
            ).toString(16), 2),
            pad(Math[darker ? 'max' : 'min'](
                parseInt(decimal[2], 10) + difference, darker ? 0 : 255
            ).toString(16), 2)
        ].join('');
};
var lighterColor = function(color, ratio) {
    return changeColor(color, ratio, false);
};
var darkerColor = function(color, ratio) {
    return changeColor(color, ratio, true);
};

// Use
var darker = darkerColor('rgba(80, 75, 52, .5)', .2);
var lighter = lighterColor('rgba(80, 75, 52, .5)', .2);

Now handles RGB(A) input, as well as hex (3 digit or 6).

Dynamically change the color button background to darker according to its parent background color

Change background-color: transparent; to background-color: rgba(0,0,0, 0.4);.

You can adjust the opacity accordingly

.a {  background-color: #309549;}
.b {  background-color: #9d0059;}
.c {  background-color: #cc3f10;}
button {  background-color:  rgba(0,0,0, 0.4); /*Changed*/  border-color: white;  color: white}

<div class="a">  <img alt="img">  <button>Test</button></div><div class="b">  <img alt="img">  <button>Test</button></div><div class="c">  <img alt="img">  <button>Test</button></div>