A PHP class to wrap imageGD PHP library into a OO class.

ImageGD.php

<?php

/**
 * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
 *
 * @version 0.2.0
 */
class ImageGD
{
    public $image_src; // the source of the image
    public $src_image; // the source image
    public $image; // the modified (or not) image
    public $written_path; // the path of first write execution
    public $last_written_path; // the path of last write execution
    public $width;
    public $height;
    public $watermark_src; // the source of the image used to watermark $image
    public $extension; // the source image extension
    public $mime_type; // the source image mime type
    private $image_create_function_name;
    private $image_write_function_name;

    /**
     * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
     *
     * @param string $image_src The path/url to the image
     *
     * @return void
     */
    public function __construct(string $image_src)
    {
        try {
            $this->type = exif_imagetype($image_src);
        } catch (Exception $e) {
            throw new \Exception('Erro fatal na recuperação dos dados da imagem: '.$e->getMessage(), 1);
        }

        if ((bool) $this->type) {
            $this->extension = image_type_to_extension($this->type, false); // false == sem . (ponto) na extensão
            $this->mime_type = image_type_to_mime_type($this->type);

            $this->image_create_function_name = 'imagecreatefrom'.$this->extension;
            $this->image_write_function_name = 'image'.$this->extension;

            $new_image = $this->image_create($image_src);

            if ($new_image !== false) {
                $this->image_src = $image_src;
                $this->src_image = $new_image;
                $this->image = $this->src_image;

                $this->width = imagesx($this->image);
                $this->height = imagesy($this->image);

                if ($this->extension == 'gif' || $this->extension == 'png') {
                    $this->resize(); // ajusta a camada transparente da imagem para não ficar com fundo negro
                }

                unset($new_image);

                return; // success
            }
        }

        $this->src_image = null;
        $this->image = null;
    }

    /**
     * @author odahcam
     *
     * @method __destruct
     * Destruct protocols to execute on object destruction
     **/
    public function __destruct()
    {
        if (is_resource($this->image)) {
            imagedestroy($this->image);
        }
        if (is_resource($this->src_image)) {
            imagedestroy($this->src_image);
        }
    }

    /**
     * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
     *
     * @param string $image_src
     *
     * @return Object ImageGD
     */
    public static function from(string $image_src)
    {
        return new self($image_src);
    }

    /**
     * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
     * @author Alex
     *
     * @source http://stackoverflow.com/a/3677986/4367683
     *
     * @param string $url
     *
     * @return boolean If the URL exists or not
     */
    public static function image_exists(string $url = null)
    {
        // This method doesn't work properly.

        $headers = get_headers($url);

        return is_array($headers) ? preg_match('/^HTTP\\/\\d+\\.\\d+\\s+2\\d\\d\\s+.*$/', $headers[0]) : false;
    }

    /**
     * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
     *
     * @param string $filename
     *
     * @return mixed $this Object or (bool) False
     */
    private function image_create(string $filename)
    {
        return call_user_func($this->image_create_function_name, $filename);
    }

    /**
     * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
     *
     * @param resource $image
     * @param string   $filename
     * @param int      $quality
     * @param int      $mode
     *
     * @return Object $this
     * @return bool   false
     */
    private function image_write($image, string $filename = null, int $quality = null, $mode = 0755)
    {
        $this->written_path = $this->written_path ?: $filename; // first write execution
        $this->last_written_path = $filename; // last write execution

        return call_user_func($this->image_write_function_name, $image, $filename, $quality);

        /*
        $dir = pathinfo($filename, PATHINFO_DIRNAME);

        if (self::makedirs($dir, $mode)) {
            return call_user_func($this->image_write_function_name, $image, $filename, $quality);
        } else {
            throw new \Exception("Não foi possível criar/adicionar permissões ao diretório desejado.");
            return false;
        }
        */
    }

    /**
     * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
     *
     * @param string $to
     * @param int    $quality
     * @param int    $mode
     *
     * @return Object $this
     * @return bool   false
     */
    public function write(string $to = null, $quality = 90, $mode = 0775)
    {
        $quality = intval($this->extension == 'png' ? $quality / 10 : $quality);

        if ($this->image_write($this->image, ($to ?: $this->image_src), $quality, $mode) !== false) {
            return $this;
        } else {
            throw new \Exception('Não foi possível escrever a imagem para '.($to ?: $this->image_src).'.', 1);

            return false;
        }
    }
    /**
     * Erases the last written image. Erases the first written image if $first == true.
     *
     * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
     *
     * @param bool $first
     *
     * @return bool
     **/
    public function erase($first = false)
    {
        if (unlink(($first) ? $this->written_path : $this->last_written_path)) {
            return $this;
        } else {
            return false;
        }
    }

    /**
     * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
     *
     * @return Object ImageGD
     **/
    public function reset()
    {
        $this->image = $this->src_image;
        $this->width = imagesx($this->src_image);
        $this->height = imagesy($this->src_image);

        return $this;
    }

    /**
     * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
     *
     * @param int  $w
     * @param int  $h
     * @param bool $to_crop
     *
     * @return Object $this
     */
    public function resize(int $w = null, int $h = null, $to_crop = false)
    {
        $crop = $resize = $src = [ // define os valores padrões
            'width' => $this->width,
            'height' => $this->height,
            'position' => [
                'x' => 0,
                'y' => 0,
            ],
        ];

        if (!(empty($w) && empty($h))) { // verifica se um tamanho foi solicitado

            $w = $w ?: $h; // corrige o tamanho de largura e altura
            $h = $h ?: $w; // para que as variáveis não fiquem nulas

            $scale_select = ($to_crop) ? 'max' : 'min';

            $scale = $scale_select($w / $src['width'], $h / $src['height']);

            $resize['width'] = $crop['width'] = floor($scale * $src['width']);
            $resize['height'] = $crop['height'] = floor($scale * $src['height']);

            if ($to_crop) {
                $crop = [
                    'width' => $w,
                    'height' => $h,
                    'position' => [
                        'x' => $resize['width'] - $w,
                        'y' => $resize['height'] - $h,
                    ],
                ];
            }
        }

        // $dst === destination
        $dst = imagecreatetruecolor($crop['width'], $crop['height']); // png ?: gif

        switch ($this->extension) {
            case 'gif':
            case 'png':
                // integer representation of the color black (rgb: 0,0,0)
                $background = imagecolorallocate($dst, 0, 0, 0);
                // removing the black from the placeholder
                imagecolortransparent($dst, $background);

                // no break
            case 'gif':
                if (self::is_animated($this->image)) {
                    // @TODO split frames and resize to keep animation
                }

                // no break
            case 'png':
                // turning off alpha blending (to ensure alpha channel information
                // is preserved, rather than removed (blending with the rest of the
                // image in the form of black))
                imagealphablending($dst, false);

                // turning on alpha channel information saving (to ensure the full range
                // of transparency is preserved)
                imagesavealpha($dst, true);
                break;

            default:
                break;
        }

        $old_max_time = ini_get('max_execution_time');

        set_time_limit(900);

        imagecopyresampled($dst, $this->image, $resize['position']['x'], $resize['position']['y'], $crop['position']['x'], $crop['position']['y'], $resize['width'], $resize['height'], $src['width'], $src['height']); // se o png tiver + de 0% de opacidade no canal alpha, então ele ficará preto

        set_time_limit($old_max_time);

        // imagedestroy($this->image);

        $this->image = $dst;
        $this->width = $crop['width'];
        $this->height = $crop['height'];

        return $this;
    }

    /**
     * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
     *
     * @param string $watermark_src
     * @param int    $size          in %
     * @param int    $margin_right  in px
     * @param int    $margin_bottom in px
     *
     * @return Object $this
     */
    public function watermark(string $watermark_src, $size = 26, $margin_right = 25, $margin_bottom = 25)
    {
        $stamp = self::from($watermark_src)->resize($size / 100 * $this->width); // resize by 26% width of $this->image

        unset($watermark_src);

        // Copy the $stamp image onto our $this->image using the margin offsets and the photo width to calculate positioning of the stamp.
        imagecopy($this->image, $stamp->image, $this->width - $stamp->width - $margin_right, $this->height - $stamp->height - $margin_bottom, 0, 0, $stamp->width, $stamp->height);

        // $this->image_write($this->image, $this->src_image, 70);

        return $this;
    }

    /**
     * @author odahcam
     * @source http://it2.php.net/manual/en/function.imagecreatefromgif.php#59787
     *
     * @param string $filename
     **/
    public static function is_animated(string $filename)
    {
        $filecontents = file_get_contents($filename);

        $str_loc = 0;
        $count = 0;
        while ($count < 2) { // There is no point in continuing after we find a 2nd frame

            $where1 = strpos($filecontents, "\x00\x21\xF9\x04", $str_loc);
            if (!$where1) {
                break;
            } else {
                $str_loc = $where1 + 1;
                $where2 = strpos($filecontents, "\x00\x2C", $str_loc);
                if (!$where2) {
                    break;
                } else {
                    if ($where1 + 8 == $where2) {
                        ++$count;
                    }
                    $str_loc = $where2 + 1;
                }
            }
        }

        return $count > 1;
    }

    /**
     * Imprime a imagem no documento.
     *
     * @author Luiz Filipe Machado Barni <luiz@h2k.com.br>
     *
     * @param void
     *
     * @return Object $this
     */
    public function dump()
    {
        header('Content-type: '.$this->mime_type);
        $this->write();

        return $this;
    }

    /**
     * Create directory if not exists.
     *
     * @param string $dirpath
     * @param int    $mode
     * @param bool   $recursive
     *
     * @return bool
     */
    public static function makedirs(string $dirpath, $mode = 0755, $recursive = true)
    {
        //$old = umask(002);
        $status = is_dir($dirpath) || mkdir($dirpath, $mode, $recursive);
        $status = ($status) ? @chmod($dirpath, 0755) : false; // use without umask()
        //umask($old);
        return $status;
    }
}