php dechex with dark colors only - php

Question

I am using php's dechex function to generate random colors as per requirements.Here is my working code.
dechex(rand(0x000000, 0xFFFFFF));
Howerver, I want to use dark colors only. I have found this code so far which generated only light colors thanks for this and this article.
However, I am yet to find a proper solution to generate only dark colors. I have tried several things like below.
'#' . substr(str_shuffle('AABBCCDDEEFF00112233445566778899AABBCCDDEEFF00112233445566778899AABBCCDDEEFF00112233445566778899'), 0, 6);
And
'#' . substr(str_shuffle('ABCDEF0123456789'), 0, 6);
But these, sometimes generating light colors randomly.
Edit:
I would like to have a solution with hex and rgb.
How Can I achieve this ?

Answer 1

Here how to get dark color for both Hex and RGB
$hexMin = 0;
$hexMax = 9;
$rgbMin = 0;
$rgbMax = 153; // Hex 99 = 153 Decimal
$hex = '#' . mt_rand($hexMin,$hexMax) . mt_rand($hexMin, $hexMax) . mt_rand($hexMin, $hexMax) . mt_rand($hexMin,$hexMax) . mt_rand($hexMin, $hexMax) . mt_rand($hexMin, $hexMax);
$rgb = 'rgb(' . mt_rand($rgbMin,$rgbMax). ',' . mt_rand($rgbMin,$rgbMax). ',' . mt_rand($rgbMin,$rgbMax). ')';

Answer 2

Put your HEX to contain only dark colors by limiting max value:
$max = 9;
'#' . mt_rand(0. $max) . mt_rand(0. $max) . mt_rand(0. $max);

Answer 3

generate a random color :
function darker_color($rgb, $darker=2) {
$hash = (strpos($rgb, '#') !== false) ? '#' : '';
$rgb = (strlen($rgb) == 7) ? str_replace('#', '', $rgb) : ((strlen($rgb) == 6) ? $rgb : false);
if(strlen($rgb) != 6) return $hash.'000000';
$darker = ($darker > 1) ? $darker : 1;
list($R16,$G16,$B16) = str_split($rgb,2);
$R = sprintf("%02X", floor(hexdec($R16)/$darker));
$G = sprintf("%02X", floor(hexdec($G16)/$darker));
$B = sprintf("%02X", floor(hexdec($B16)/$darker));
return $hash.$R.$G.$B;
}
$color = '#'.dechex(rand(0x000000, 0xFFFFFF));
$dark = darker_color($color);
echo "$color => $dark";
Even if a random generated color is dark , the function pick up a darker color . normaly it goes to black color .

Answer 4

The main thing you seem to want is to ensure that each pair of hex digits is below a certain level once you've generated a random number. As rand() will generate any value up to the limit, my approach is to keep your original limit of 0xffffff but once the number has been generated, apply a bitwise and (&) to clear the high bits for each byte...
echo '#'.dechex(rand(0x000000, 0xFFFFFF) & 0x3f3f3f);
You can tweak the 0x3f3f3f to a limit which you want to set to limit the maximum value.