How to convert RGBA color codes to 8 Digit Hex in PHP?-CodePudding

I am finding examples converting 8 digit hex colors into RGBA, but not the other way around.

Is there a PHP function that will convert RGBA color codes into 8 digit Hex? (The kind that start with "&H")

Something like:

$colorcode = 'rgba(123,100,23,.5);

$eightdigit = convertto8($colorcode);

Here is a function I put together based one of the answers, but I the last alpha channel is always coming out to zero:

function rgbtohex($string) {

    $string = str_replace("rgba","",$string);
    $string = str_replace("rgb","",$string);
    $string = str_replace("(","",$string);
    $string = str_replace(")","",$string);
    
    
    $colorexplode = explode(",",$string);

    $hex = '&H';

    foreach($colorexplode AS $c) {

        echo "C" . $c . " " . dechex($c) . "<br><br>";
    
        $hex .= dechex($c);
  
}

return $hex;

  
}

Then if I test it:

$rgb = 'rgba(123,223,215,.9)';
$rgb = rgbtohex($rgb);
echo $rgb;

This produces the following:

&H7bdfd70 which only has 7 characters instead of 8.

Also, the alpha channel (.9) always comes out to zero, so that doesn't appear to be working correctly.

CodePudding user response：

You can use the dechex() function to convert each param of your rgba color to a 2 hex digit.

So in your example you have to concat each part of the rgba to get the hex value of your color : dechex(123).dechex(100).dechex(23).dechex(0.5)

CodePudding user response：

You can use the printf() family of functions to convert to a properly padded hex string. Decimals cannot be represented in hex, so the value is taken as a fraction of 0xFF.

$rgba = "rgba(123,100,23,.5)";

// get the values
preg_match_all("/([\\d.] )/", $rgba, $matches);

// adjust opacity
$matches[1][3] *= 255;

// output
$hex = vsprintf("&HXXXX", $matches[1]);
echo $hex;

Output:

&H7B64177F