Convert Hex to RGB for imagegif function

Question

The function below is designed to take an input hex (with or without the "#" prefix) and apply the color update to the portion of the image between startPixel and endPixel.

I can get the function to work fine on localhost tests when (1) supplying red, green, blue and (2) running the file directly as a stand alone (ie, just saving the contents of the function to a file and executing it).

However, I have two problems I can't seem to resolve. (1) I need to pass in a hex and get the function to work without requiring rgb hard codes and (2) I need the function to work inside my functions.php file in wordpress while saving my theme options. I'm getting a "failed to open stream" error each time I try to call the function on save.

` function:

 function set_theme_color($hex)
 {
 //hexToRGB($hex); DOES NOT WORK. ALWAYS RETURNS BLACK
 $token = "images/sidebar-bg";

 $red = 0;
 $green = 0;
 $blue = 202;

 $startPixel = 601;
 $endPixel = 760;

   $img = imagecreatefromgif('images/sidebar-bg.gif');

 $color = imagecolorallocate($img, $red, $green, $blue);

 for ($i = $startPixel-1; $i < $endPixel; $i++)
 {
  imagesetpixel($img, $i, 0, $color);
 }

 imagegif($img, $token.'.gif');
 }

 function hexToRGB ($hexColor)
 {
 $output = array();
 $output['red']   = hexdec($hexColor[0].$hexColor[1]);
 $output['green'] = hexdec($hexColor[2].$hexColor[3]);
 $output['blue']  = hexdec($hexColor[4].$hexColor[5]);

 return $output;
 }

 set_theme_color('#cccccc');

`

Answer 1

Your hexToRGB function is not taking the possibility of the # sign into account. For parsing the color codes, I'd use a regex:

function hexToRGB ($hexColor)
{
    if( preg_match( '/^#?([a-h0-9]{2})([a-h0-9]{2})([a-h0-9]{2})$/i', $hexColor, $matches ) )
    {
        return array(
            'red' => hexdec( $matches[ 1 ] ),
            'green' => hexdec( $matches[ 2 ] ),
            'blue' => hexdec( $matches[ 3 ] )
        );
    }
    else
    {
        return array( 0, 0, 0 );
    }
}

Your cannot open stream error is most likely due to file permissions. Make sure to grant the permissions mode 777 on the file you're trying to write to.