<?php

/**
 * Create an animated GIF from multiple images
 *
 * @update by gesior, php 8.0 compatibility
 *
 * @version 1.0
 * @link https://github.com/Sybio/GifCreator
 * @author Sybio (Clément Guillemain  / @Sybio01)
 * @license http://opensource.org/licenses/gpl-license.php GNU Public License
 * @copyright Clément Guillemain
 */
class GifCreator
{
    /**
     * @var string The gif string source (old: this->GIF)
     */
    private $gif;

    /**
     * @var string Encoder version (old: this->VER)
     */
    private $version;

    /**
     * @var boolean Check the image is build or not (old: this->IMG)
     */
    private $imgBuilt;

    /**
     * @var array Frames string sources (old: this->BUF)
     */
    private $frameSources;

    /**
     * @var integer Gif loop (old: this->LOP)
     */
    private $loop;

    /**
     * @var integer Gif dis (old: this->DIS)
     */
    private $dis;

    /**
     * @var integer Gif color (old: this->COL)
     */
    private $colour;

    /**
     * @var array (old: this->ERR)
     */
    private $errors;

    // Methods
    // ===================================================================================

    /**
     * Constructor
     */
    public function __construct()
    {
        $this->reset();

        // Static data
        $this->version = 'GifCreator: Under development';
        $this->errors = array(
            'ERR00' => 'Does not supported function for only one image.',
            'ERR01' => 'Source is not a GIF image.',
            'ERR02' => 'You have to give resource image variables, image URL or image binary sources in $frames array.',
            'ERR03' => 'Does not make animation from animated GIF source.',
        );
    }

    /**
     * Create the GIF string (old: GIFEncoder)
     *
     * @param array $frames An array of frame: can be file paths, resource image variables, binary sources or image URLs
     * @param array $durations An array containing the duration of each frame
     * @param integer $loop Number of GIF loops before stopping animation (Set 0 to get an infinite loop)
     *
     * @return string The GIF string source
     */
    public function create($frames = array(), $durations = array(), $loop = 0)
    {
        if (!is_array($frames) && !is_array($durations)) {
            throw new \Exception($this->version . ': ' . $this->errors['ERR00']);
        }

        $this->loop = ($loop > -1) ? $loop : 0;
        $this->dis = 2;

        for ($i = 0; $i < count($frames); $i++) {
            if ($frames[$i] instanceof GdImage || is_resource($frames[$i])) { // Resource var

                $resourceImg = $frames[$i];

                ob_start();
                imagegif($frames[$i]);
                $this->frameSources[] = ob_get_contents();
                ob_end_clean();
            } elseif (is_string($frames[$i])) { // File path or URL or Binary source code

                if (file_exists($frames[$i]) || filter_var($frames[$i], FILTER_VALIDATE_URL)) { // File path

                    $frames[$i] = file_get_contents($frames[$i]);
                }

                $resourceImg = imagecreatefromstring($frames[$i]);

                ob_start();
                imagegif($resourceImg);
                $this->frameSources[] = ob_get_contents();
                ob_end_clean();
            } else { // Fail

                throw new \Exception($this->version . ': ' . $this->errors['ERR02']);
            }

            if ($i == 0) {
                $colour = imagecolortransparent($resourceImg);
            }

            if (substr($this->frameSources[$i], 0, 6) != 'GIF87a' && substr(
                    $this->frameSources[$i],
                    0,
                    6
                ) != 'GIF89a') {
                throw new \Exception($this->version . ': ' . $i . ' ' . $this->errors['ERR01']);
            }

            for ($j = (13 + 3 * (2 << (ord($this->frameSources[$i] [10]) & 0x07))), $k = true; $k; $j++) {
                switch ($this->frameSources[$i] [$j]) {
                    case '!':

                        if ((substr($this->frameSources[$i], ($j + 3), 8)) == 'NETSCAPE') {
                            throw new \Exception(
                                $this->version . ': ' . $this->errors['ERR03'] . ' (' . ($i + 1) . ' source).'
                            );
                        }

                        break;

                    case ';':

                        $k = false;
                        break;
                }
            }

            unset($resourceImg);
        }

        if (isset($colour)) {
            $this->colour = $colour;
        } else {
            $red = $green = $blue = 0;
            $this->colour = ($red > -1 && $green > -1 && $blue > -1) ? ($red | ($green << 8) | ($blue << 16)) : -1;
        }

        $this->gifAddHeader();

        for ($i = 0; $i < count($this->frameSources); $i++) {
            $this->addGifFrames($i, $durations[$i]);
        }

        $this->gifAddFooter();

        return $this->gif;
    }

    // Internals
    // ===================================================================================

    /**
     * Add the header gif string in its source (old: GIFAddHeader)
     */
    public function gifAddHeader()
    {
        $cmap = 0;

        if (ord($this->frameSources[0] [10]) & 0x80) {
            $cmap = 3 * (2 << (ord($this->frameSources[0] [10]) & 0x07));

            $this->gif .= substr($this->frameSources[0], 6, 7);
            $this->gif .= substr($this->frameSources[0], 13, $cmap);
            $this->gif .= "!\377\13NETSCAPE2.0\3\1" . $this->encodeAsciiToChar($this->loop) . "\0";
        }
    }

    /**
     * Add the frame sources to the GIF string (old: GIFAddFrames)
     *
     * @param integer $i
     * @param integer $d
     */
    public function addGifFrames($i, $d)
    {
        $Locals_str = 13 + 3 * (2 << (ord($this->frameSources[$i] [10]) & 0x07));

        $Locals_end = strlen($this->frameSources[$i]) - $Locals_str - 1;
        $Locals_tmp = substr($this->frameSources[$i], $Locals_str, $Locals_end);

        $Global_len = 2 << (ord($this->frameSources[0] [10]) & 0x07);
        $Locals_len = 2 << (ord($this->frameSources[$i] [10]) & 0x07);

        $Global_rgb = substr($this->frameSources[0], 13, 3 * (2 << (ord($this->frameSources[0] [10]) & 0x07)));
        $Locals_rgb = substr($this->frameSources[$i], 13, 3 * (2 << (ord($this->frameSources[$i] [10]) & 0x07)));

        $Locals_ext = "!\xF9\x04" . chr(($this->dis << 2) + 0) . chr(($d >> 0) & 0xFF) . chr(
                ($d >> 8) & 0xFF
            ) . "\x0\x0";

        if ($this->colour > -1 && ord($this->frameSources[$i] [10]) & 0x80) {
            for ($j = 0; $j < (2 << (ord($this->frameSources[$i] [10]) & 0x07)); $j++) {
                if (ord($Locals_rgb [3 * $j + 0]) == (($this->colour >> 16) & 0xFF) &&
                    ord($Locals_rgb [3 * $j + 1]) == (($this->colour >> 8) & 0xFF) &&
                    ord($Locals_rgb [3 * $j + 2]) == (($this->colour >> 0) & 0xFF)
                ) {
                    $Locals_ext = "!\xF9\x04" . chr(($this->dis << 2) + 1) . chr(($d >> 0) & 0xFF) . chr(
                            ($d >> 8) & 0xFF
                        ) . chr($j) . "\x0";
                    break;
                }
            }
        }

        switch ($Locals_tmp [0]) {
            case '!':

                $Locals_img = substr($Locals_tmp, 8, 10);
                $Locals_tmp = substr($Locals_tmp, 18, strlen($Locals_tmp) - 18);

                break;

            case ',':

                $Locals_img = substr($Locals_tmp, 0, 10);
                $Locals_tmp = substr($Locals_tmp, 10, strlen($Locals_tmp) - 10);

                break;
        }

        if (ord($this->frameSources[$i] [10]) & 0x80 && $this->imgBuilt) {
            if ($Global_len == $Locals_len) {
                if ($this->gifBlockCompare($Global_rgb, $Locals_rgb, $Global_len)) {
                    $this->gif .= $Locals_ext . $Locals_img . $Locals_tmp;
                } else {
                    $byte = ord($Locals_img [9]);
                    $byte |= 0x80;
                    $byte &= 0xF8;
                    $byte |= (ord($this->frameSources[0] [10]) & 0x07);
                    $Locals_img [9] = chr($byte);
                    $this->gif .= $Locals_ext . $Locals_img . $Locals_rgb . $Locals_tmp;
                }
            } else {
                $byte = ord($Locals_img [9]);
                $byte |= 0x80;
                $byte &= 0xF8;
                $byte |= (ord($this->frameSources[$i] [10]) & 0x07);
                $Locals_img [9] = chr($byte);
                $this->gif .= $Locals_ext . $Locals_img . $Locals_rgb . $Locals_tmp;
            }
        } else {
            $this->gif .= $Locals_ext . $Locals_img . $Locals_tmp;
        }

        $this->imgBuilt = true;
    }

    /**
     * Add the gif string footer char (old: GIFAddFooter)
     */
    public function gifAddFooter()
    {
        $this->gif .= ';';
    }

    /**
     * Compare two block and return the version (old: GIFBlockCompare)
     *
     * @param string $globalBlock
     * @param string $localBlock
     * @param integer $length
     *
     * @return integer
     */
    public function gifBlockCompare($globalBlock, $localBlock, $length)
    {
        for ($i = 0; $i < $length; $i++) {
            if ($globalBlock [3 * $i + 0] != $localBlock [3 * $i + 0] ||
                $globalBlock [3 * $i + 1] != $localBlock [3 * $i + 1] ||
                $globalBlock [3 * $i + 2] != $localBlock [3 * $i + 2]) {
                return 0;
            }
        }

        return 1;
    }

    /**
     * Encode an ASCII char into a string char (old: GIFWord)
     *
     * $param integer $char ASCII char
     *
     * @return string
     */
    public function encodeAsciiToChar($char)
    {
        return (chr($char & 0xFF) . chr(($char >> 8) & 0xFF));
    }

    /**
     * Reset and clean the current object
     */
    public function reset()
    {
        $this->frameSources;
        $this->gif = 'GIF89a'; // the GIF header
        $this->imgBuilt = false;
        $this->loop = 0;
        $this->dis = 2;
        $this->colour = -1;
    }

    // Getter / Setter
    // ===================================================================================

    /**
     * Get the final GIF image string (old: GetAnimation)
     *
     * @return string
     */
    public function getGif()
    {
        return $this->gif;
    }
}