Get the average color (HEX) from an JPEG image.

average-color.php

<?php

/**
 * Get the average color from an JPEG image.
 *
 * @param string $image_path Explicit path to the image.
 *
 * @return string Returns a HEX value.
 */
function average_color(string $image_path): string
{
    $image = imagecreatefromjpeg($image_path);
    $tmp_image = imagecreatetruecolor(1, 1);
    $x = imagesx($image);
    $y = imagesy($image);
    imagecopyresampled($tmp_image, $image, 0, 0, 0, 0, 1, 1, $x, $y);
    $rgb = imagecolorat($tmp_image, 0, 0);
    $red = ($rgb >> 16) & 0xff;
    $green = ($rgb >> 8) & 0xff;
    $blue = $rgb & 0xff;
    $hex = sprintf('#%02x%02x%02x', $red, $green, $blue);

    return $hex;
}

/**
 * Example code.
 */
$image_path = '/path/to/image.jpeg';
$average_color = average_color($image_path);

echo $average_color;