How to convert color to hexadecimal in php

php method to convert colors to hexadecimal: first create a PHP sample file; then use the "function RGBToHex($rgb){...}" method to convert RGB colors to hexadecimal colors That’s it.

The operating environment of this article: Windows7 system, PHP7.1 version, DELL G3 computer

Hexadecimal color and How to convert RGB color values ​​to each other

The hexadecimal color value is usually expressed as #FFFFFF, and currently it is also reduced to #FFF, provided that the two digits must be the same, such as #FEFEFE. It cannot be reduced. The RGB color format is composed of three groups of numbers from 0 to 255, which represent the color values ​​of red, green, and blue respectively.

So, converting hexadecimal to RGB color values ​​is actually to convert the two digits after the # sign into decimal as one unit.

The code is as follows:

/** 
* 将16进制颜色转换为RGB
* author www.jb51.net
*/ 
function hex2rgb($hexColor){
 $color=str_replace('#','',$hexColor);
 if (strlen($color)> 3){
 $rgb=array(
  'r'=>hexdec(substr($color,0,2)),
  'g'=>hexdec(substr($color,2,2)),
  'b'=>hexdec(substr($color,4,2))
 );
 }else{
 $r=substr($color,0,1). substr($color,0,1);
 $g=substr($color,1,1). substr($color,1,1);
 $b=substr($color,2,1). substr($color,2,1);
 $rgb=array( 
  'r'=>hexdec($r),
  'g'=>hexdec($g),
  'b'=>hexdec($b)
 );
 }
 return $rgb;
}

Another way of writing

/**
   * 十六进制转RGB
   * @param string $color 16进制颜色值
   * @return array
   */
  public static function hex2rgb($color) {
    $hexColor = str_replace('#', '', $color);
    $lens = strlen($hexColor);
    if ($lens != 3 && $lens != 6) {
      return false;
    }
    $newcolor = '';
    if ($lens == 3) {
      for ($i = 0; $i < $lens; $i++) {
        $newcolor .= $hexColor[$i] . $hexColor[$i];
      }
    } else {
      $newcolor = $hexColor;
    }
    $hex = str_split($newcolor, 2);
    $rgb = [];
    foreach ($hex as $key => $vls) {
      $rgb[] = hexdec($vls);
    }
    return $rgb;
  }

[Recommended learning: PHP video tutorial]

RGB color and hexadecimal color conversion

/**
   * RGB转 十六进制
   * @param $rgb RGB颜色的字符串 如：rgb(255,255,255);
   * @return string 十六进制颜色值 如：#FFFFFF
   */
  function RGBToHex($rgb){
    $regexp = "/^rgb\(([0-9]{0,3})\,\s*([0-9]{0,3})\,\s*([0-9]{0,3})\)/";
    $re = preg_match($regexp, $rgb, $match);
    $re = array_shift($match);
    $hexColor = "#";
    $hex = array('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F');
    for ($i = 0; $i < 3; $i++) {
      $r = null;
      $c = $match[$i];
      $hexAr = array();
      while ($c > 16) {
        $r = $c % 16;
        $c = ($c / 16) >> 0;
        array_push($hexAr, $hex[$r]);
      }
      array_push($hexAr, $hex[$c]);
      $ret = array_reverse($hexAr);
      $item = implode(&#39;&#39;, $ret);
      $item = str_pad($item, 2, &#39;0&#39;, STR_PAD_LEFT);
      $hexColor .= $item;
    }
    return $hexColor;
  }
  /**
   * 十六进制 转 RGB
   */
  function hex2rgb($hexColor) {
    $color = str_replace(&#39;#&#39;, &#39;&#39;, $hexColor);
    if (strlen($color) > 3) {
      $rgb = array(
        &#39;r&#39; => hexdec(substr($color, 0, 2)),
        &#39;g&#39; => hexdec(substr($color, 2, 2)),
        &#39;b&#39; => hexdec(substr($color, 4, 2))
      );
    } else {
      $color = $hexColor;
      $r = substr($color, 0, 1) . substr($color, 0, 1);
      $g = substr($color, 1, 1) . substr($color, 1, 1);
      $b = substr($color, 2, 1) . substr($color, 2, 1);
      $rgb = array(
        &#39;r&#39; => hexdec($r),
        &#39;g&#39; => hexdec($g),
        &#39;b&#39; => hexdec($b)
      );
    }
    return $rgb;
  }

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