system/classes/colorutils.php

<?php
namespace Habari;
class ColorUtils
{
  public static function rgb_rgbarr( $r, $g, $b )
  {
    return array_map( 'round', array( 'r' => $r, 'g' => $g, 'b' => $b ) );
  }
  
  public static function hsv_hsvarr( $h, $s, $v )
  {
    return array_map( 'round', array( 'h' => $h, 's' => $s, 'v' => $v ) );
  }
  
  public static function hex_rgb( $hex_string )
  {
    $hex_string = ltrim( $hex_string, '#' );
    if ( ! preg_match( '/^[0-9a-f]+$/i', $hex_string ) ) {
      return Error::raise( _t( 'Not a valid hex color.' ) );
    }
    
    $normalized = '';
    
    switch ( strlen( $hex_string ) ) {
      case 3:
        // 'fed' = 'ffeedd'
        for ( $i = 0; $i < 3; $i++ ) {
          $normalized .= $hex_string{$i} . $hex_string{$i};
        }
        break;
      case 6:
        // already normal
        $normalized = $hex_string;
        break;
      case 2:
      case 4:
        // who uses this anyway!
        $normalized = $hex_string . str_repeat( '0', 6 - strlen( $hex_string ) );
        break;
      default:
        return Error::raise( _t( 'Not a valid color format.' ) );
    }
    
    return self::rgb_rgbarr(
      hexdec( substr( $normalized, 0, 2 ) ), 
      hexdec( substr( $normalized, 2, 2 ) ),
      hexdec( substr( $normalized, 4, 2 ) )
    );
  }
  
  public static function rgb_hex( $rgb_arr )
  {
    $hex_string = sprintf( '%02x%02x%02x', $rgb_arr['r'], $rgb_arr['g'], $rgb_arr['b'] );
    
    return $hex_string;
  }
  
  public static function rgb_hsv( $rgb_arr )
  {
    $var_R = ($rgb_arr['r'] / 255);
    $var_G = ($rgb_arr['g'] / 255);
    $var_B = ($rgb_arr['b'] / 255);

    $var_Min = min($var_R, $var_G, $var_B);
    $var_Max = max($var_R, $var_G, $var_B);
    $del_Max = $var_Max - $var_Min;

    $V = $var_Max;

    if( $del_Max == 0 ) {
      $H = 0;
      $S = 0;
    } else {
      $S = $del_Max / $var_Max;

      $del_R = ((($var_Max - $var_R) / 6) + ($del_Max / 2)) / $del_Max;
      $del_G = ((($var_Max - $var_G) / 6) + ($del_Max / 2)) / $del_Max;
      $del_B = ((($var_Max - $var_B) / 6) + ($del_Max / 2)) / $del_Max;

      if( $var_R == $var_Max ) {
        $H = $del_B - $del_G;
      }
      elseif( $var_G == $var_Max ) {
        $H = (1 / 3) + $del_R - $del_B;
      }
      elseif( $var_B == $var_Max ) {
        $H = (2 / 3) + $del_G - $del_R;
      }
      else {
        $H = 0;  // This never happens, since one of the three is always the max
      }

      if( $H < 0 ) {
        $H += 1;
      }
      if( $H > 1 ) {
        $H -= 1;
      }
    }
    return self::hsv_hsvarr($H * 360, $S * 255, $V * 255);
  }
  
  public static function hsv_rgb( $hsv_arr )
  {
    if ( $hsv_arr['s'] == 0 ) {
      // grey
      $r = $g = $b = $hsv_arr['v'];
    }
    else {
      $h = $hsv_arr['h'] / 60; // degrees to sectors
      $s = $hsv_arr['s'] / 100; // percent to fraction
      $f = $h - floor( $h );
      
      $p = $hsv_arr['v'] * ( 1 - $s );
      $q = $hsv_arr['v'] * ( 1 - $s * $f );
      $t = $hsv_arr['v'] * ( 1 - $s * ( 1 - $f ) );
      
      switch ( floor( $h ) ) {
        case 0: // first sector
          $r = $hsv_arr['v'];
          $g = $t;
          $b = $p;
          break;
        case 1: // second sector
          $r = $q;
          $g = $hsv_arr['v'];
          $b = $p;
          break;
        case 2: // third sector
          $r = $p;
          $g = $hsv_arr['v'];
          $b = $t;
          break;
        case 3: // fourth sector
          $r = $p;
          $g = $q;
          $b = $hsv_arr['v'];
          break;
        case 4: // fifth sector
          $r = $t;
          $g = $p;
          $b = $hsv_arr['v'];
          break;
        case 5: // sixth sector
          $r = $hsv_arr['v'];
          $g = $p;
          $b = $q;
          break;
      }
    }
  
    return self::rgb_rgbarr( $r, $g, $b );
  }
}

?>