<?php
/**
 * Created by PhpStorm.
 * User: zheev
 * Date: 26.01.18
 * Time: 0:49
 */

echo '<form action="/" enctype="multipart/form-data" method="post">
        <input type="file" name="foto" />
        <input type="submit" name="submit" />
    </form>';

$mime = [
    'image/png',
    'image/jpeg',
    'image/jpeg',
    'image/jpg',
    'image/gif',
    'image/bmp',
    'image/vnd.microsoft.icon',
    'image/tiff',
    'image/tiff',
    'image/svg+xml',
    'image/svg+xml',
];

if($_POST['submit'])
{

    $sum = 0;

    $name = $_FILES['foto']['tmp_name'];

    $sizes = getimagesize($name);

    if(in_array($sizes['mime'], $mime))
    {
        $type = explode('/', $sizes['mime']);

        if($type[1] == 'png')
        {

            $photo = imagecreatefrompng($name);

        }elseif($type[1] == 'jpeg')
        {

            $photo = imagecreatefromjpeg($name);

        }


        for($w = 0; $w <= $sizes[0]; $w++)
        {

            for($h=0; $h <= $sizes[1]; $h++)
            {
                $color = imagecolorat($photo, $w, $h);
                // получаем цвета
                $arr_col = imagecolorsforindex($photo, $color);

                if($arr_col['red'] == 255 and $arr_col['green'] == 255 and $arr_col['blue'] == 255)
                {
                    $sum = $sum + 1;
                }
            }

        }

        echo $sum;
    }

}