ImageManipulator.php

<?php
class ImageManipulator
{
    /**
     * @var int
     */
    protected $width;

    /**
     * @var int
     */
    protected $height;

    /**
     * @var resource
     */
    protected $image;

    /**
     * Image manipulator constructor
     * 
     * @param string $file OPTIONAL Path to image file or image data as string
     * @return void
     */
    public function __construct($file = null)
    {
        if (null !== $file) {
            if (is_file($file)) {
                $this->setImageFile($file);
            } else {
                $this->setImageString($file);
            }
        }
    }

    /**
     * Set image resource from file
     * 
     * @param string $file Path to image file
     * @return ImageManipulator for a fluent interface
     * @throws InvalidArgumentException
     */
    public function setImageFile($file)
    {
        if (!(is_readable($file) && is_file($file))) {
            throw new InvalidArgumentException("Image file $file is not readable");
        }

        if (is_resource($this->image)) {
            imagedestroy($this->image);
        }

        list ($this->width, $this->height, $type) = getimagesize($file);

        switch ($type) {
            case IMAGETYPE_GIF  :
                $this->image = imagecreatefromgif($file);
                break;
            case IMAGETYPE_JPEG :
                $this->image = imagecreatefromjpeg($file);
                break;
            case IMAGETYPE_PNG  :
                $this->image = imagecreatefrompng($file);
                break;
            default             :
                throw new InvalidArgumentException("Image type $type not supported");
        }

        return $this;
    }
    
    /**
     * Set image resource from string data
     * 
     * @param string $data
     * @return ImageManipulator for a fluent interface
     * @throws RuntimeException
     */
    public function setImageString($data)
    {
        if (is_resource($this->image)) {
            imagedestroy($this->image);
        }

        if (!$this->image = imagecreatefromstring($data)) {
            throw new RuntimeException('Cannot create image from data string');
        }
        $this->width = imagesx($this->image);
        $this->height = imagesy($this->image);
        return $this;
    }

    /**
     * Resamples the current image
     *
     * @param int  $width                New width
     * @param int  $height               New height
     * @param bool $constrainProportions Constrain current image proportions when resizing
     * @return ImageManipulator for a fluent interface
     * @throws RuntimeException
     */
    public function resample($width, $height, $constrainProportions = true)
    {
        if (!is_resource($this->image)) {
            throw new RuntimeException('No image set');
        }
        if ($constrainProportions) {
            if ($this->height >= $this->width) {
                $width  = round($height / $this->height * $this->width);
            } else {
                $height = round($width / $this->width * $this->height);
            }
        }
        $temp = imagecreatetruecolor($width, $height);
        imagecopyresampled($temp, $this->image, 0, 0, 0, 0, $width, $height, $this->width, $this->height);
        return $this->_replace($temp);
    }
    
    /**
     * Enlarge canvas
     * 
     * @param int   $width  Canvas width
     * @param int   $height Canvas height
     * @param array $rgb    RGB colour values
     * @param int   $xpos   X-Position of image in new canvas, null for centre
     * @param int   $ypos   Y-Position of image in new canvas, null for centre
     * @return ImageManipulator for a fluent interface
     * @throws RuntimeException
     */
    public function enlargeCanvas($width, $height, array $rgb = array(), $xpos = null, $ypos = null)
    {
        if (!is_resource($this->image)) {
            throw new RuntimeException('No image set');
        }
        
        $width = max($width, $this->width);
        $height = max($height, $this->height);
        
        $temp = imagecreatetruecolor($width, $height);
        if (count($rgb) == 3) {
            $bg = imagecolorallocate($temp, $rgb[0], $rgb[1], $rgb[2]);
            imagefill($temp, 0, 0, $bg);
        }
        
        if (null === $xpos) {
            $xpos = round(($width - $this->width) / 2);
        }
        if (null === $ypos) {
            $ypos = round(($height - $this->height) / 2);
        }
        
        imagecopy($temp, $this->image, (int) $xpos, (int) $ypos, 0, 0, $this->width, $this->height);
        return $this->_replace($temp);
    }
    
    /**
     * Crop image
     * 
     * @param int|array $x1 Top left x-coordinate of crop box or array of coordinates
     * @param int       $y1 Top left y-coordinate of crop box
     * @param int       $x2 Bottom right x-coordinate of crop box
     * @param int       $y2 Bottom right y-coordinate of crop box
     * @return ImageManipulator for a fluent interface
     * @throws RuntimeException
     */
    public function crop($x1, $y1 = 0, $x2 = 0, $y2 = 0)
    {
        if (!is_resource($this->image)) {
            throw new RuntimeException('No image set');
        }
        if (is_array($x1) && 4 == count($x1)) {
            list($x1, $y1, $x2, $y2) = $x1;
        }
        
        $x1 = max($x1, 0);
        $y1 = max($y1, 0);
        
        $x2 = min($x2, $this->width);
        $y2 = min($y2, $this->height);
        
        $width = $x2 - $x1;
        $height = $y2 - $y1;
        
        $temp = imagecreatetruecolor($width, $height);
        imagecopy($temp, $this->image, 0, 0, $x1, $y1, $width, $height);
        
        return $this->_replace($temp);
    }
    
    /**
     * Replace current image resource with a new one
     * 
     * @param resource $res New image resource
     * @return ImageManipulator for a fluent interface
     * @throws UnexpectedValueException
     */
    protected function _replace($res)
    {
        if (!is_resource($res)) {
            throw new UnexpectedValueException('Invalid resource');
        }
        if (is_resource($this->image)) {
            imagedestroy($this->image);
        }
        $this->image = $res;
        $this->width = imagesx($res);
        $this->height = imagesy($res);
        return $this;
    }
    
    /**
     * Save current image to file
     * 
     * @param string $fileName
     * @return void
     * @throws RuntimeException
     */
    public function save($fileName, $type = IMAGETYPE_JPEG)
    {
        $dir = dirname($fileName);
        if (!is_dir($dir)) {
            if (!mkdir($dir, 0755, true)) {
                throw new RuntimeException('Error creating directory ' . $dir);
            }
        }
        
        try {
            switch ($type) {
                case IMAGETYPE_GIF  :
                    if (!imagegif($this->image, $fileName)) {
                        throw new RuntimeException;
                    }
                    break;
                case IMAGETYPE_PNG  :
                    if (!imagepng($this->image, $fileName)) {
                        throw new RuntimeException;
                    }
                    break;
                case IMAGETYPE_JPEG :
                default             :
                    if (!imagejpeg($this->image, $fileName, 95)) {
                        throw new RuntimeException;
                    }
            }
        } catch (Exception $ex) {
            throw new RuntimeException('Error saving image file to ' . $fileName);
        }
    }

    /**
     * Returns the GD image resource
     *
     * @return resource
     */
    public function getResource()
    {
        return $this->image;
    }

    /**
     * Get current image resource width
     *
     * @return int
     */
    public function getWidth()
    {
        return $this->width;
    }

    /**
     * Get current image height
     *
     * @return int
     */
    public function getHeight()
    {
        return $this->height;
    }
}

You must replace is_resource() with is_object() to make this library compatible with PHP 8.1. Otherwise, it would throw No image set