Fix resource usages in OC_Image

This makes sure using resource or GdImage (PHP>=8) behaves the same.

Signed-off-by: Côme Chilliet <come.chilliet@nextcloud.com>

lib/private/Avatar/UserAvatar.php

 	/**
 	 * Returns an image from several sources.
 	 *
-	 * @param IImage|resource|string $data An image object, imagedata or path to the avatar
+	 * @param IImage|resource|string|\GdImage $data An image object, imagedata or path to the avatar
 	 * @return IImage
 	 */
 	private function getAvatarImage($data) {
 		}
 
 		$img = new OC_Image();
-		if (is_resource($data) && get_resource_type($data) === 'gd') {
+		if (
+			(is_resource($data) && get_resource_type($data) === 'gd') ||
+			(is_object($data) && get_class($data) === \GdImage::class)
+			) {
 			$img->setResource($data);
 		} elseif (is_resource($data)) {
 			$img->loadFromFileHandle($data);

lib/private/Preview/Bitmap.php

 
 		//new bitmap image object
 		$image = new \OC_Image();
-		$image->loadFromData($bp);
+		$image->loadFromData((string) $bp);
 		//check if image object is valid
 		return $image->valid() ? $image : null;
 	}

lib/private/Preview/HEIC.php

 
 		//new bitmap image object
 		$image = new \OC_Image();
-		$image->loadFromData($bp);
+		$image->loadFromData((string) $bp);
 		//check if image object is valid
 		return $image->valid() ? $image : null;
 	}

lib/private/Preview/SVG.php

 
 		//new image object
 		$image = new \OC_Image();
-		$image->loadFromData($svg);
+		$image->loadFromData((string) $svg);
 		//check if image object is valid
 		if ($image->valid()) {
 			$image->scaleDownToFit($maxX, $maxY);

lib/private/legacy/OC_Image.php

 		if (is_resource($this->resource)) {
 			return true;
 		}
-		if (is_object($this->resource) && get_class($this->resource) === 'GdImage') {
+		if (is_object($this->resource) && get_class($this->resource) === \GdImage::class) {
 			return true;
 		}
 
 	}
 
 	/**
-	 * @param resource Returns the image resource in any.
+	 * @param resource|\GdImage $resource
 	 * @throws \InvalidArgumentException in case the supplied resource does not have the type "gd"
 	 */
 	public function setResource($resource) {
 			return;
 		}
 		// PHP 8 has real objects for GD stuff
-		if (is_object($resource) && get_class($resource) === 'GdImage') {
+		if (is_object($resource) && get_class($resource) === \GdImage::class) {
 			$this->resource = $resource;
 			return;
 		}
 	}
 
 	/**
-	 * @return resource Returns the image resource in any.
+	 * @return resource|\GdImage Returns the image resource in any.
 	 */
 	public function resource() {
 		return $this->resource;
 	 * It is the responsibility of the caller to position the pointer at the correct place and to close the handle again.
 	 *
 	 * @param resource $handle
-	 * @return resource|false An image resource or false on error
+	 * @return resource|\GdImage|false An image resource or false on error
 	 */
 	public function loadFromFileHandle($handle) {
 		$contents = stream_get_contents($handle);
 	 * Loads an image from a local file.
 	 *
 	 * @param bool|string $imagePath The path to a local file.
-	 * @return bool|resource An image resource or false on error
+	 * @return bool|resource|\GdImage An image resource or false on error
 	 */
 	public function loadFromFile($imagePath = false) {
 		// exif_imagetype throws "read error!" if file is less than 12 byte
 	 * Loads an image from a string of data.
 	 *
 	 * @param string $str A string of image data as read from a file.
-	 * @return bool|resource An image resource or false on error
+	 * @return bool|resource|\GdImage An image resource or false on error
 	 */
 	public function loadFromData($str) {
-		if (is_resource($str)) {
+		if (!is_string($str)) {
 			return false;
 		}
 		$this->resource = @imagecreatefromstring($str);
 		if ($this->fileInfo) {
 			$this->mimeType = $this->fileInfo->buffer($str);
 		}
-		if (is_resource($this->resource)) {
+		if ($this->valid()) {
 			imagealphablending($this->resource, false);
 			imagesavealpha($this->resource, true);
 		}
 	 * Loads an image from a base64 encoded string.
 	 *
 	 * @param string $str A string base64 encoded string of image data.
-	 * @return bool|resource An image resource or false on error
+	 * @return bool|resource|\GdImage An image resource or false on error
 	 */
 	public function loadFromBase64($str) {
 		if (!is_string($str)) {
 	 * @param string $fileName <p>
 	 * Path to the BMP image.
 	 * </p>
-	 * @return bool|resource an image resource identifier on success, <b>FALSE</b> on errors.
+	 * @return bool|resource|\GdImage an image resource identifier on success, <b>FALSE</b> on errors.
 	 */
 	private function imagecreatefrombmp($fileName) {
 		if (!($fh = fopen($fileName, 'rb'))) {
 		$result = $this->resizeNew($maxSize);
 		imagedestroy($this->resource);
 		$this->resource = $result;
-		return is_resource($result);
+		return $this->valid();
 	}
 
 	/**
 	 * @param $maxSize
-	 * @return resource | bool
+	 * @return resource|bool|\GdImage
 	 */
 	private function resizeNew($maxSize) {
 		if (!$this->valid()) {
 		$result = $this->preciseResizeNew($width, $height);
 		imagedestroy($this->resource);
 		$this->resource = $result;
-		return is_resource($result);
+		return $this->valid();
 	}
 
 
 	/**
 	 * @param int $width
 	 * @param int $height
-	 * @return resource | bool
+	 * @return resource|bool|\GdImage
 	 */
 	public function preciseResizeNew(int $width, int $height) {
 		if (!$this->valid()) {
 		$result = $this->cropNew($x, $y, $w, $h);
 		imagedestroy($this->resource);
 		$this->resource = $result;
-		return is_resource($result);
+		return $this->valid();
 	}
 
 	/**
 	 * @link http://www.programmierer-forum.de/imagebmp-gute-funktion-gefunden-t143716.htm
 	 * @author mgutt <marc@gutt.it>
 	 * @version 1.00
-	 * @param resource $im
+	 * @param resource|\GdImage $im
 	 * @param string $fileName [optional] <p>The path to save the file to.</p>
 	 * @param int $bit [optional] <p>Bit depth, (default is 24).</p>
 	 * @param int $compression [optional]

lib/public/IImage.php

 	public function save($filePath = null, $mimeType = null);
 
 	/**
-	 * @return resource Returns the image resource in any.
+	 * @return resource|\GdImage Returns the image resource in any.
 	 * @since 8.1.0
 	 */
 	public function resource();

psalm.xml

 			<errorLevel type="suppress">
 				<referencedClass name="OCA\GroupFolders\Mount\GroupFolderStorage"/>
 				<referencedClass name="OCA\TwoFactorNextcloudNotification\Controller\APIController"/>
+				<!-- Classes from PHP>=8 (needed to be able to use \GdImage::class) -->
+				<referencedClass name="GdImage" />
 			</errorLevel>
 		</UndefinedClass>
 		<UndefinedFunction>
 				<!-- Helper classes for sharing API integration from other apps -->
 				<referencedClass name="OCA\Deck\Sharing\ShareAPIHelper" />
 				<referencedClass name="OCA\Talk\Share\Helper\DeletedShareAPIController" />
+				<!-- Classes from PHP>=8 -->
+				<referencedClass name="GdImage" />
 			</errorLevel>
 		</UndefinedDocblockClass>
 	</issueHandlers>