Detect "overall average" color of the picture

You can use PHP to get an array of the color palette like so:

<?php function colorPalette($imageFile, $numColors, $granularity = 5) {    $granularity = max(1, abs((int)$granularity));    $colors = array();    $size = @getimagesize($imageFile);    if($size === false)    {       user_error("Unable to get image size data");       return false;    }    $img = @imagecreatefromjpeg($imageFile);   // Andres mentioned in the comments the above line only loads jpegs,    // and suggests that to load any file type you can use this:   // $img = @imagecreatefromstring(file_get_contents($imageFile));    if(!$img)    {       user_error("Unable to open image file");       return false;    }    for($x = 0; $x < $size[0]; $x += $granularity)    {       for($y = 0; $y < $size[1]; $y += $granularity)       {          $thisColor = imagecolorat($img, $x, $y);          $rgb = imagecolorsforindex($img, $thisColor);          $red = round(round(($rgb['red'] / 0x33)) * 0x33);          $green = round(round(($rgb['green'] / 0x33)) * 0x33);          $blue = round(round(($rgb['blue'] / 0x33)) * 0x33);          $thisRGB = sprintf('%02X%02X%02X', $red, $green, $blue);          if(array_key_exists($thisRGB, $colors))          {             $colors[$thisRGB]++;          }          else          {             $colors[$thisRGB] = 1;          }       }    }    arsort($colors);    return array_slice(array_keys($colors), 0, $numColors); } // sample usage: $palette = colorPalette('rmnp8.jpg', 10, 4); echo "<table>\n"; foreach($palette as $color) {    echo "<tr><td style='background-color:#$color;width:2em;'> </td><td>#$color</td></tr>\n"; } echo "</table>\n";

Which gives you an array whose values are higher for how often that color has been used.

EDITA commenter asked how to use this on all files in a directory, here it is:

    if ($handle = opendir('./path/to/images')) {        while (false !== ($file = readdir($handle))) {           $palette = colorPalette($file, 10, 4);           echo "<table>\n";            foreach($palette as $color) {                echo "<tr><td style='background-color:#$color;width:2em;'> </td><td>#$color</td></tr>\n";            }            echo "</table>\n";        }        closedir($handle);    }

might not want to do this on too many files, but it's your server.

Alternatively if you'd rather use Javascript Lokesh's Color-Theif library does exactly what you're looking for.

Combining JKirchartz and Alexander Hugestrand answer:

 function getAverage($sourceURL){    $image = imagecreatefromjpeg($sourceURL);    $scaled = imagescale($image, 1, 1, IMG_BICUBIC);     $index = imagecolorat($scaled, 0, 0);    $rgb = imagecolorsforindex($scaled, $index);     $red = round(round(($rgb['red'] / 0x33)) * 0x33);     $green = round(round(($rgb['green'] / 0x33)) * 0x33);     $blue = round(round(($rgb['blue'] / 0x33)) * 0x33);     return sprintf('#%02X%02X%02X', $red, $green, $blue);  }

Tried and tested, returns hex string.

$img = glob('img/*');foreach ($img as $key => $value) {    $info = getimagesize($value);    $mime = $info['mime'];    switch ($mime) {        case 'image/jpeg':            $image_create_func = 'imagecreatefromjpeg';            break;        case 'image/png':            $image_create_func = 'imagecreatefrompng';            break;        case 'image/gif':            $image_create_func = 'imagecreatefromgif';            break;    }    $avg = $image_create_func($value);    list($width, $height) = getimagesize($value);    $tmp = imagecreatetruecolor(1, 1);    imagecopyresampled($tmp, $avg, 0, 0, 0, 0, 1, 1, $width, $height);    $rgb = imagecolorat($tmp, 0, 0);    $r = ($rgb >> 16) & 0xFF;    $g = ($rgb >> 8) & 0xFF;    $b = $rgb & 0xFF;    echo '<div style="text-align:center; vertical-align: top; display:inline-block; width:100px; height:150px; margin:5px; padding:5px; background-color:rgb('.$r.','.$g.','.$b.');">';    echo '<img style="width:auto; max-height:100%; max-width: 100%; vertical-align:middle; height:auto; margin-bottom:5px;" src="'.$value.'">';    echo '</div>';

you can get the value of the average color with $r, $g, & $bresample the image is much more better than only scale it !