<?php
/**
 * VizHash_GD
 *
 * Visual Hash implementation in php4+GD,
 * stripped down and modified version for PrivateBin
 *
 * @link      https://sebsauvage.net/wiki/doku.php?id=php:vizhash_gd
 * @copyright 2012 Sébastien SAUVAGE (sebsauvage.net)
 * @license   https://www.opensource.org/licenses/zlib-license.php The zlib/libpng License
 * @version   0.0.5 beta PrivateBin 1.6.2
 */

namespace PrivateBin;

/**
 * Vizhash16x16
 *
 * Example:
 * $vz = new Vizhash16x16();
 * $data = $vz->generate(sha512('hello'));
 * header('Content-type: image/png');
 * echo $data;
 * exit;
 */
class Vizhash16x16
{
    /**
     * hash values
     *
     * @access private
     * @var    array
     */
    private $VALUES;

    /**
     * index of current value
     *
     * @access private
     * @var    int
     */
    private $VALUES_INDEX;

    /**
     * image width
     *
     * @access private
     * @var    int
     */
    private $width;

    /**
     * image height
     *
     * @access private
     * @var    int
     */
    private $height;

    /**
     * constructor
     *
     * @access public
     */
    public function __construct()
    {
        $this->width  = 16;
        $this->height = 16;
    }

    /**
     * Generate a 16x16 png corresponding to $text.
     *
     * The given text should to be 128 to 150 characters long
     *
     * @access public
     * @param  string $text
     * @return string PNG data. Or empty string if GD is not available.
     */
    public function generate($text)
    {
        if (!function_exists('gd_info')) {
            return '';
        }

        $textlen = strlen($text);

        // We convert the hash into an array of integers.
        $this->VALUES = array();
        for ($i = 0; $i < $textlen; $i = $i + 2) {
            array_push($this->VALUES, hexdec(substr($text, $i, 2)));
        }
        $this->VALUES_INDEX = 0; // to walk the array.

        // Then use these integers to drive the creation of an image.
        $image = imagecreatetruecolor($this->width, $this->height);

        $r = $r0 = $this->getInt();
        $g = $g0 = $this->getInt();
        $b = $b0 = $this->getInt();

        // First, create an image with a specific gradient background.
        $op = 'v';
        if (($this->getInt() % 2) == 0) {
            $op = 'h';
        }
        $image = $this->degrade($image, $op, array($r0, $g0, $b0), array(0, 0, 0));

        for ($i = 0; $i < 7; ++$i) {
            $action = $this->getInt();
            $color  = imagecolorallocate($image, $r, $g, $b);
            $r      = $r0      = ($r0 + $this->getInt() / 25) % 256;
            $g      = $g0      = ($g0 + $this->getInt() / 25) % 256;
            $b      = $b0      = ($b0 + $this->getInt() / 25) % 256;
            $this->drawshape($image, $action, $color);
        }

        $color = imagecolorallocate($image, $this->getInt(), $this->getInt(), $this->getInt());
        $this->drawshape($image, $this->getInt(), $color);
        ob_start();
        imagepng($image);
        $imagedata = ob_get_contents();
        ob_end_clean();
        imagedestroy($image);

        return $imagedata;
    }

    /**
     * Returns a single integer from the $VALUES array (0...255)
     *
     * @access private
     * @return int
     */
    private function getInt()
    {
        $v = $this->VALUES[$this->VALUES_INDEX];
        ++$this->VALUES_INDEX;
        $this->VALUES_INDEX %= count($this->VALUES); // Warp around the array
        return $v;
    }

    /**
     * Returns a single integer from the array (roughly mapped to image width)
     *
     * @access private
     * @return int
     */
    private function getX()
    {
        return $this->width * $this->getInt() / 256;
    }

    /**
     * Returns a single integer from the array (roughly mapped to image height)
     *
     * @access private
     * @return int
     */
    private function getY()
    {
        return $this->height * $this->getInt() / 256;
    }

    /**
     * Gradient function
     *
     * taken from:
     * @link   https://www.supportduweb.com/scripts_tutoriaux-code-source-41-gd-faire-un-degrade-en-php-gd-fonction-degrade-imagerie.html
     *
     * @access private
     * @param  resource $img
     * @param  string $direction
     * @param  array $color1
     * @param  array $color2
     * @return resource
     */
    private function degrade($img, $direction, $color1, $color2)
    {
        if ($direction == 'h') {
            $size    = imagesx($img);
            $sizeinv = imagesy($img);
        } else {
            $size    = imagesy($img);
            $sizeinv = imagesx($img);
        }
        $diffs = array(
            ($color2[0] - $color1[0]) / $size,
            ($color2[1] - $color1[1]) / $size,
            ($color2[2] - $color1[2]) / $size,
        );
        for ($i = 0; $i < $size; ++$i) {
            $r = $color1[0] + ($diffs[0] * $i);
            $g = $color1[1] + ($diffs[1] * $i);
            $b = $color1[2] + ($diffs[2] * $i);
            if ($direction == 'h') {
                imageline($img, $i, 0, $i, $sizeinv, imagecolorallocate($img, $r, $g, $b));
            } else {
                imageline($img, 0, $i, $sizeinv, $i, imagecolorallocate($img, $r, $g, $b));
            }
        }
        return $img;
    }

    /**
     * Draw a shape
     *
     * @access private
     * @param  resource $image
     * @param  int $action
     * @param  int $color
     */
    private function drawshape($image, $action, $color)
    {
        switch ($action % 7) {
            case 0:
                imagefilledrectangle($image, $this->getX(), $this->getY(), $this->getX(), $this->getY(), $color);
                break;
            case 1:
            case 2:
                imagefilledellipse($image, $this->getX(), $this->getY(), $this->getX(), $this->getY(), $color);
                break;
            case 3:
                $points = array($this->getX(), $this->getY(), $this->getX(), $this->getY(), $this->getX(), $this->getY(), $this->getX(), $this->getY());
                imagefilledpolygon($image, $points, 4, $color);
                break;
            default:
                $start = $this->getInt() * 360 / 256;
                $end   = $start + $this->getInt() * 180 / 256;
                imagefilledarc($image, $this->getX(), $this->getY(), $this->getX(), $this->getY(), $start, $end, $color, IMG_ARC_PIE);
        }
    }
}