diff --git a/.github/workflows/phpunit-integration.yml b/.github/workflows/phpunit-integration.yml
index 70b75d7d..27e96cf4 100644
--- a/.github/workflows/phpunit-integration.yml
+++ b/.github/workflows/phpunit-integration.yml
@@ -133,7 +133,7 @@ jobs:
         if: failure()
         uses: actions/upload-artifact@v4
         with:
-          name: logs
+          name: logs-integrationtests-${{ matrix.backend }}
           path: data/*.log
 
 
diff --git a/.github/workflows/phpunit.yml b/.github/workflows/phpunit.yml
index 429374e2..aa84358a 100644
--- a/.github/workflows/phpunit.yml
+++ b/.github/workflows/phpunit.yml
@@ -15,8 +15,7 @@ jobs:
     runs-on: ubuntu-22.04
 
     strategy:
-      # do not stop on another job's failure
-      fail-fast: false
+      fail-fast: true
       matrix:
         php-versions: ['8.3']
         databases: ['sqlite']
diff --git a/README.md b/README.md
index 11c1b233..56e7aa6a 100644
--- a/README.md
+++ b/README.md
@@ -217,6 +217,8 @@ For processing PDF files, the external command line tool [`OCRmyPDF`](https://gi
 ### Images
 For processing single images (currently `jpg` and `png` are supported), `ocrmypdf` converts the image to a PDF. The converted PDF file will then be OCR processed and saved as a new file with the original filename and the extension `.pdf` (for example `myImage.jpg` will be saved to `myImage.jpg.pdf`). The original image fill will remain untouched.
 
+Note about PNG alpha channel: The OCR processing will remove (flatten) the alpha/transparency channel from PNG images before conversion. Transparent areas are filled with a white background to make the OCR process possible with `ocmypdf`. This behavior applies automatically to PNG images processed by the app. See [this issue](https://github.com/R0Wi-DEV/workflow_ocr/issues/295) for details.
+
 ## Troubleshooting
 
 ### Generic troubleshooting guide
diff --git a/lib/AppInfo/Application.php b/lib/AppInfo/Application.php
index 680fc613..9647a724 100644
--- a/lib/AppInfo/Application.php
+++ b/lib/AppInfo/Application.php
@@ -56,7 +56,9 @@
 use OCA\WorkflowOcr\Wrapper\IAppApiWrapper;
 use OCA\WorkflowOcr\Wrapper\ICommand;
 use OCA\WorkflowOcr\Wrapper\IFilesystem;
+use OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions;
 use OCA\WorkflowOcr\Wrapper\IViewFactory;
+use OCA\WorkflowOcr\Wrapper\PhpNativeFunctions;
 use OCA\WorkflowOcr\Wrapper\ViewFactory;
 use OCP\AppFramework\App;
 use OCP\AppFramework\Bootstrap\IBootContext;
@@ -93,6 +95,7 @@ public function register(IRegistrationContext $context): void {
 		$context->registerServiceAlias(INotificationService::class, NotificationService::class);
 		$context->registerServiceAlias(IApiClient::class, ApiClient::class);
 		$context->registerServiceAlias(ICommandLineUtils::class, CommandLineUtils::class);
+		$context->registerServiceAlias(IPhpNativeFunctions::class, PhpNativeFunctions::class);
 		$context->registerServiceAlias(IAppApiWrapper::class, AppApiWrapper::class);
 
 		// BUG #43
diff --git a/lib/OcrProcessors/IOcrProcessor.php b/lib/OcrProcessors/IOcrProcessor.php
index bca2209d..a5f3a0c4 100644
--- a/lib/OcrProcessors/IOcrProcessor.php
+++ b/lib/OcrProcessors/IOcrProcessor.php
@@ -23,7 +23,9 @@
 
 namespace OCA\WorkflowOcr\OcrProcessors;
 
+use OCA\WorkflowOcr\Exception\OcrAlreadyDoneException;
 use OCA\WorkflowOcr\Exception\OcrNotPossibleException;
+use OCA\WorkflowOcr\Exception\OcrResultEmptyException;
 use OCA\WorkflowOcr\Model\GlobalSettings;
 use OCA\WorkflowOcr\Model\WorkflowSettings;
 use OCP\Files\File;
@@ -35,6 +37,8 @@ interface IOcrProcessor {
 	 * @param WorkflowSettings $settings The settings to be used for this specific workflow
 	 * @param GlobalSettings $globalSettings The global settings configured for all OCR workflows on this system
 	 * @return OcrProcessorResult
+	 * @throws OcrAlreadyDoneException
+	 * @throws OcrResultEmptyException
 	 * @throws OcrNotPossibleException
 	 */
 	public function ocrFile(File $file, WorkflowSettings $settings, GlobalSettings $globalSettings) : OcrProcessorResult;
diff --git a/lib/OcrProcessors/Local/OcrMyPdfBasedProcessor.php b/lib/OcrProcessors/Local/OcrMyPdfBasedProcessor.php
index d7b29680..2c3f81e7 100644
--- a/lib/OcrProcessors/Local/OcrMyPdfBasedProcessor.php
+++ b/lib/OcrProcessors/Local/OcrMyPdfBasedProcessor.php
@@ -23,34 +23,35 @@
 
 namespace OCA\WorkflowOcr\OcrProcessors\Local;
 
-use OCA\WorkflowOcr\Exception\OcrAlreadyDoneException;
-use OCA\WorkflowOcr\Exception\OcrNotPossibleException;
-use OCA\WorkflowOcr\Exception\OcrResultEmptyException;
 use OCA\WorkflowOcr\Helper\ISidecarFileAccessor;
 use OCA\WorkflowOcr\Model\GlobalSettings;
 use OCA\WorkflowOcr\Model\WorkflowSettings;
 use OCA\WorkflowOcr\OcrProcessors\ICommandLineUtils;
-use OCA\WorkflowOcr\OcrProcessors\IOcrProcessor;
-use OCA\WorkflowOcr\OcrProcessors\OcrProcessorResult;
+use OCA\WorkflowOcr\OcrProcessors\OcrProcessorBase;
 use OCA\WorkflowOcr\Wrapper\ICommand;
-use OCP\Files\File;
+use OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions;
 use Psr\Log\LoggerInterface;
 
-abstract class OcrMyPdfBasedProcessor implements IOcrProcessor {
+abstract class OcrMyPdfBasedProcessor extends OcrProcessorBase {
 	public function __construct(
 		private ICommand $command,
-		private LoggerInterface $logger,
+		protected LoggerInterface $logger,
 		private ISidecarFileAccessor $sidecarFileAccessor,
 		private ICommandLineUtils $commandLineUtils,
+		IPhpNativeFunctions $phpNativeFunctions,
 	) {
+		parent::__construct($logger, $phpNativeFunctions);
 	}
 
-	public function ocrFile(File $file, WorkflowSettings $settings, GlobalSettings $globalSettings): OcrProcessorResult {
+	protected function doOcrProcessing($fileResource, string $fileName, WorkflowSettings $settings, GlobalSettings $globalSettings): array {
 		$additionalCommandlineArgs = $this->getAdditionalCommandlineArgs($settings, $globalSettings);
 		$sidecarFile = $this->sidecarFileAccessor->getOrCreateSidecarFile();
 		$commandStr = 'ocrmypdf ' . $this->commandLineUtils->getCommandlineArgs($settings, $globalSettings, $sidecarFile, $additionalCommandlineArgs) . ' - - || exit $? ; cat';
 
-		$inputFileContent = $file->getContent();
+		$inputFileContent = $this->phpNative->streamGetContents($fileResource);
+		if ($inputFileContent === false) {
+			return [false, null, null, -1, 'Failed to read file content from stream'];
+		}
 
 		$this->command
 			->setCommand($commandStr)
@@ -64,11 +65,7 @@ public function ocrFile(File $file, WorkflowSettings $settings, GlobalSettings $
 		$exitCode = $this->command->getExitCode();
 
 		if (!$success) {
-			# Gracefully handle OCR_MODE_SKIP_FILE (ExitCode.already_done_ocr)
-			if ($exitCode === 6) {
-				throw new OcrAlreadyDoneException('File ' . $file->getPath() . ' appears to contain text so it may not need OCR. Message: ' . $errorOutput . ' ' . $stdErr);
-			}
-			throw new OcrNotPossibleException('OCRmyPDF exited abnormally with exit-code ' . $exitCode . ' for file ' . $file->getPath() . '. Message: ' . $errorOutput . ' ' . $stdErr);
+			return [false, null, null, $exitCode, $errorOutput . ' ' . $stdErr];
 		}
 
 		if ($stdErr !== '' || $errorOutput !== '') {
@@ -80,20 +77,9 @@ public function ocrFile(File $file, WorkflowSettings $settings, GlobalSettings $
 		}
 
 		$ocrFileContent = $this->command->getOutput();
-
-		if (!$ocrFileContent) {
-			throw new OcrResultEmptyException('OCRmyPDF did not produce any output for file ' . $file->getPath());
-		}
-
 		$recognizedText = $this->sidecarFileAccessor->getSidecarFileContent();
 
-		if (!$recognizedText) {
-			$this->logger->info('Temporary sidecar file at \'{path}\' was empty', ['path' => $sidecarFile]);
-		}
-
-		$this->logger->debug('OCR processing was successful');
-
-		return new OcrProcessorResult($ocrFileContent, 'pdf', $recognizedText);
+		return [true, $ocrFileContent, $recognizedText, $exitCode, null];
 	}
 
 	/**
diff --git a/lib/OcrProcessors/OcrProcessorBase.php b/lib/OcrProcessors/OcrProcessorBase.php
new file mode 100644
index 00000000..2f47dff3
--- /dev/null
+++ b/lib/OcrProcessors/OcrProcessorBase.php
@@ -0,0 +1,135 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright Copyright (c) 2025 Robin Windey <ro.windey@gmail.com>
+ *
+ *  @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OCA\WorkflowOcr\OcrProcessors;
+
+use OCA\WorkflowOcr\Exception\OcrAlreadyDoneException;
+use OCA\WorkflowOcr\Exception\OcrNotPossibleException;
+use OCA\WorkflowOcr\Exception\OcrResultEmptyException;
+use OCA\WorkflowOcr\Model\GlobalSettings;
+use OCA\WorkflowOcr\Model\WorkflowSettings;
+use OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions;
+use OCP\Files\File;
+use Psr\Log\LoggerInterface;
+
+/**
+ * Base class for all OCR processors.
+ */
+abstract class OcrProcessorBase implements IOcrProcessor {
+	public function __construct(
+		protected LoggerInterface $logger,
+		protected IPhpNativeFunctions $phpNative,
+	) {
+	}
+
+	public function ocrFile(File $file, WorkflowSettings $settings, GlobalSettings $globalSettings): OcrProcessorResult {
+		$fileName = $file->getName();
+		$fileResource = $this->doFilePreprocessing($file);
+		try {
+			[$success, $fileContent, $recognizedText, $exitCode, $errorMessage] = $this->doOcrProcessing($fileResource, $fileName, $settings, $globalSettings);
+			if (!$success) {
+				$this->throwException($errorMessage, $exitCode);
+			}
+			if (!$recognizedText) {
+				$this->logger->info('Recognized text was empty');
+			}
+			return $fileContent ? new OcrProcessorResult($fileContent, $recognizedText) : throw new OcrResultEmptyException('OCRmyPDF did not produce any output for file ' . $fileName);
+		} finally {
+			if (is_resource($fileResource)) {
+				fclose($fileResource);
+			}
+		}
+	}
+
+	/**
+	 * Perform the actual OCR processing. Implementation is specific to the OCR processor. Might be local or remote.
+	 * Should return [$success, $fileContent, $recognizedText, $exitCode, $errorMessage]
+	 * @param resource $fileResource
+	 * @param string $fileName
+	 * @param WorkflowSettings $settings
+	 * @param GlobalSettings $globalSettings
+	 * @return array{bool, string|null, string|null, int, string|null} [$success, $fileContent, $recognizedText, $exitCode, $errorMessage]
+	 */
+	abstract protected function doOcrProcessing($fileResource, string $fileName, WorkflowSettings $settings, GlobalSettings $globalSettings): array;
+
+	/**
+	 * @return resource|false
+	 */
+	private function doFilePreprocessing(File $file) {
+		return $file->getMimeType() !== 'image/png' ? $file->fopen('rb') : $this->removeAlphaChannelFromImage($file);
+	}
+
+	/**
+	 * @return resource|false
+	 */
+	private function removeAlphaChannelFromImage(File $file) {
+		// Remove any alpha channel from the PNG image (if any)
+		$imageResource = null;
+		$destroyImageResource = false;
+		try {
+			$this->logger->debug('Checking if PNG has alpha channel');
+
+			$imageResource = $file->fopen('rb');
+			$image = new \Imagick();
+			$image->readImageFile($imageResource, $file->getName());
+			$alphaChannel = $image->getImageAlphaChannel();
+
+			if (!$alphaChannel) {
+				$this->logger->debug('PNG does not have alpha channel, no need to remove it');
+				return $imageResource;
+			}
+
+			$this->logger->debug('PNG has alpha channel, removing it');
+			$image->setImageAlphaChannel(\Imagick::ALPHACHANNEL_REMOVE);
+			$image->mergeImageLayers(\Imagick::LAYERMETHOD_FLATTEN);
+			$imageBlob = $image->getImageBlob();
+			$stream = $this->phpNative->fopen('php://temp', 'r+');
+			if ($stream === false) {
+				throw new \RuntimeException('Failed to create temporary stream for alpha channel removal');
+			}
+			fwrite($stream, $imageBlob);
+			rewind($stream);
+			$destroyImageResource = true;
+			return $stream;
+		} finally {
+			// Only close the original image resource if we did not return it
+			if (isset($imageResource) && is_resource($imageResource) && $destroyImageResource) {
+				fclose($imageResource);
+			}
+			if (isset($image) && is_object($image)) {
+				$image->clear();
+				$image->destroy();
+			}
+		}
+	}
+
+	/**
+	 * Throws an appropriate exception based on the error message and exit code.
+	 */
+	private function throwException($errorMessage, $exitCode) {
+		if ($exitCode === 6) {
+			throw new OcrAlreadyDoneException('File appears to contain text so it may not need OCR. Message: ' . $errorMessage);
+		}
+		throw new OcrNotPossibleException($errorMessage);
+	}
+}
diff --git a/lib/OcrProcessors/OcrProcessorFactory.php b/lib/OcrProcessors/OcrProcessorFactory.php
index ce939a0c..55751215 100644
--- a/lib/OcrProcessors/OcrProcessorFactory.php
+++ b/lib/OcrProcessors/OcrProcessorFactory.php
@@ -30,6 +30,7 @@
 use OCA\WorkflowOcr\OcrProcessors\Remote\WorkflowOcrRemoteProcessor;
 use OCA\WorkflowOcr\Service\IOcrBackendInfoService;
 use OCA\WorkflowOcr\Wrapper\ICommand;
+use OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions;
 use OCP\AppFramework\Bootstrap\IRegistrationContext;
 use Psr\Container\ContainerInterface;
 use Psr\Log\LoggerInterface;
@@ -72,13 +73,15 @@ public static function registerOcrProcessors(IRegistrationContext $context) : vo
 				$c->get(ICommand::class),
 				$c->get(LoggerInterface::class),
 				$c->get(ISidecarFileAccessor::class),
-				$c->get(ICommandLineUtils::class)), false);
+				$c->get(ICommandLineUtils::class),
+				$c->get(IPhpNativeFunctions::class)), false);
 		$context->registerService(ImageOcrProcessor::class, fn (ContainerInterface $c)
 			=> new ImageOcrProcessor(
 				$c->get(ICommand::class),
 				$c->get(LoggerInterface::class),
 				$c->get(ISidecarFileAccessor::class),
-				$c->get(ICommandLineUtils::class)), false);
+				$c->get(ICommandLineUtils::class),
+				$c->get(IPhpNativeFunctions::class)), false);
 	}
 
 	/** @inheritdoc */
diff --git a/lib/OcrProcessors/OcrProcessorResult.php b/lib/OcrProcessors/OcrProcessorResult.php
index e1d6b07a..0af7cf93 100644
--- a/lib/OcrProcessors/OcrProcessorResult.php
+++ b/lib/OcrProcessors/OcrProcessorResult.php
@@ -30,14 +30,11 @@ class OcrProcessorResult {
 	/** @var string */
 	private $fileContent;
 	/** @var string */
-	private $fileExtension;
-	/** @var string */
 	private $recognizedText;
 
 
-	public function __construct(string $fileContent, string $fileExtension, string $recognizedText) {
+	public function __construct(string $fileContent, string $recognizedText) {
 		$this->fileContent = $fileContent;
-		$this->fileExtension = $fileExtension;
 		$this->recognizedText = $recognizedText;
 	}
 
@@ -45,10 +42,6 @@ public function getFileContent(): string {
 		return $this->fileContent;
 	}
 
-	public function getFileExtension(): string {
-		return $this->fileExtension;
-	}
-
 	public function getRecognizedText(): string {
 		return $this->recognizedText;
 	}
diff --git a/lib/OcrProcessors/Remote/WorkflowOcrRemoteProcessor.php b/lib/OcrProcessors/Remote/WorkflowOcrRemoteProcessor.php
index c86c6d1d..d66b483f 100644
--- a/lib/OcrProcessors/Remote/WorkflowOcrRemoteProcessor.php
+++ b/lib/OcrProcessors/Remote/WorkflowOcrRemoteProcessor.php
@@ -23,34 +23,29 @@
 
 namespace OCA\WorkflowOcr\OcrProcessors\Remote;
 
-use OCA\WorkflowOcr\Exception\OcrAlreadyDoneException;
-use OCA\WorkflowOcr\Exception\OcrNotPossibleException;
 use OCA\WorkflowOcr\Model\GlobalSettings;
 use OCA\WorkflowOcr\Model\WorkflowSettings;
 use OCA\WorkflowOcr\OcrProcessors\ICommandLineUtils;
-use OCA\WorkflowOcr\OcrProcessors\IOcrProcessor;
-use OCA\WorkflowOcr\OcrProcessors\OcrProcessorResult;
+use OCA\WorkflowOcr\OcrProcessors\OcrProcessorBase;
 use OCA\WorkflowOcr\OcrProcessors\Remote\Client\IApiClient;
 use OCA\WorkflowOcr\OcrProcessors\Remote\Client\Model\ErrorResult;
-use OCP\Files\File;
 use Psr\Log\LoggerInterface;
 
 /**
  * OCR Processor which utilizes the Workflow OCR Backend remote service to perform OCR.
  */
-class WorkflowOcrRemoteProcessor implements IOcrProcessor {
+class WorkflowOcrRemoteProcessor extends OcrProcessorBase {
 	public function __construct(
 		private IApiClient $apiClient,
 		private ICommandLineUtils $commandLineUtils,
-		private LoggerInterface $logger,
+		protected LoggerInterface $logger,
+		\OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions $phpNative,
 	) {
-
+		parent::__construct($logger, $phpNative);
 	}
 
-	public function ocrFile(File $file, WorkflowSettings $settings, GlobalSettings $globalSettings): OcrProcessorResult {
+	protected function doOcrProcessing($fileResource, string $fileName, WorkflowSettings $settings, GlobalSettings $globalSettings): array {
 		$ocrMyPdfParameters = $this->commandLineUtils->getCommandlineArgs($settings, $globalSettings);
-		$fileResource = $file->fopen('rb');
-		$fileName = $file->getName();
 
 		$this->logger->debug('Sending OCR request to remote backend');
 		$apiResult = $this->apiClient->processOcr($fileResource, $fileName, $ocrMyPdfParameters);
@@ -60,17 +55,9 @@ public function ocrFile(File $file, WorkflowSettings $settings, GlobalSettings $
 			$resultMessage = $apiResult->getMessage();
 			$exitCode = $apiResult->getOcrMyPdfExitCode();
 
-			# Gracefully handle OCR_MODE_SKIP_FILE (ExitCode.already_done_ocr)
-			if ($exitCode === 6) {
-				throw new OcrAlreadyDoneException('File ' . $file->getPath() . ' appears to contain text so it may not need OCR. Message: ' . $resultMessage);
-			}
-			throw new OcrNotPossibleException($resultMessage);
+			return [false, null, null, $exitCode, $resultMessage];
 		}
 
-		return new OcrProcessorResult(
-			base64_decode($apiResult->getFileContent()),
-			pathinfo($apiResult->getFilename(), PATHINFO_EXTENSION),
-			$apiResult->getRecognizedText()
-		);
+		return [true, base64_decode($apiResult->getFileContent()), $apiResult->getRecognizedText(), 0, null];
 	}
 }
diff --git a/lib/Service/OcrService.php b/lib/Service/OcrService.php
index e7777e10..e92a39c6 100644
--- a/lib/Service/OcrService.php
+++ b/lib/Service/OcrService.php
@@ -52,6 +52,7 @@
 class OcrService implements IOcrService {
 	private const FILE_VERSION_LABEL_KEY = 'label';
 	private const FILE_VERSION_LABEL_VALUE = 'Before OCR';
+	private const PDF_FILE_EXTENSION = 'pdf';
 
 	/** @var IOcrProcessorFactory */
 	private $ocrProcessorFactory;
@@ -328,7 +329,6 @@ private function doPostProcessing(Node $file, string $uid, WorkflowSettings $set
 		$fileId = $file->getId();
 		$fileContent = $result->getFileContent();
 		$originalFileExtension = $file->getExtension();
-		$newFileExtension = $result->getFileExtension();
 
 		// Only create a new file version if the file OCR result was not empty #130
 		if ($result->getRecognizedText() !== '') {
@@ -337,7 +337,7 @@ private function doPostProcessing(Node $file, string $uid, WorkflowSettings $set
 				$this->setFileVersionsLabel($file, $uid, self::FILE_VERSION_LABEL_VALUE);
 			}
 
-			$newFilePath = $this->determineNewFilePath($file, $originalFileExtension, $newFileExtension);
+			$newFilePath = $this->determineNewFilePath($file, $originalFileExtension);
 			$this->createNewFileVersion($newFilePath, $fileContent, $fileMtime);
 		}
 
@@ -354,19 +354,18 @@ private function doPostProcessing(Node $file, string $uid, WorkflowSettings $set
 	 *
 	 * @param Node $file The original file node for which the OCR processing has been succeeded.
 	 * @param string $originalFileExtension The original file extension.
-	 * @param string $newFileExtension The new file extension to be applied.
 	 * @return string The new file path with the updated extension.
 	 */
-	private function determineNewFilePath(Node $file, string $originalFileExtension, string $newFileExtension): string {
+	private function determineNewFilePath(Node $file, string $originalFileExtension): string {
 		$filePath = $file->getPath();
-		if ($originalFileExtension !== $newFileExtension) {
+		if ($originalFileExtension !== self::PDF_FILE_EXTENSION) {
 			// If the extension changed, will create a new file with the new extension
-			return $filePath . '.' . $newFileExtension;
+			return "$filePath." . self::PDF_FILE_EXTENSION;
 		}
 		if (!$file->isUpdateable()) {
 			// Add suffix '_OCR' if original file cannot be updated
 			$fileInfo = pathinfo($filePath);
-			return $fileInfo['dirname'] . '/' . $fileInfo['filename'] . '_OCR.' . $newFileExtension;
+			return $fileInfo['dirname'] . '/' . $fileInfo['filename'] . '_OCR.' . self::PDF_FILE_EXTENSION;
 		}
 		// By returning the original file path, we will create a new file version of the original file
 		return $filePath;
diff --git a/lib/Wrapper/IPhpNativeFunctions.php b/lib/Wrapper/IPhpNativeFunctions.php
new file mode 100644
index 00000000..14219a50
--- /dev/null
+++ b/lib/Wrapper/IPhpNativeFunctions.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\WorkflowOcr\Wrapper;
+
+interface IPhpNativeFunctions {
+	/**
+	 * Wrapper around PHP's native stream_get_contents.
+	 * Returns string on success or false on failure.
+	 *
+	 * @param resource $handle
+	 * @return string|false
+	 */
+	public function streamGetContents($handle);
+
+	/**
+	 * Wrapper around PHP's native fopen.
+	 * Returns a resource on success or false on failure.
+	 *
+	 * @param string $filename
+	 * @param string $mode
+	 * @return resource|false
+	 */
+	public function fopen(string $filename, string $mode);
+}
diff --git a/lib/Wrapper/PhpNativeFunctions.php b/lib/Wrapper/PhpNativeFunctions.php
new file mode 100644
index 00000000..95fde2f4
--- /dev/null
+++ b/lib/Wrapper/PhpNativeFunctions.php
@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\WorkflowOcr\Wrapper;
+
+class PhpNativeFunctions implements IPhpNativeFunctions {
+	public function streamGetContents($handle) {
+		return stream_get_contents($handle);
+	}
+
+	public function fopen(string $filename, string $mode) {
+		return fopen($filename, $mode);
+	}
+}
diff --git a/tests/Integration/LocalBackendTest.php b/tests/Integration/LocalBackendTest.php
index b91eac3f..56548996 100644
--- a/tests/Integration/LocalBackendTest.php
+++ b/tests/Integration/LocalBackendTest.php
@@ -125,4 +125,28 @@ public function testWorkflowOcrLocalBackendSkipText(): void {
 		$this->assertInstanceOf(TextRecognizedEvent::class, $textRecognizedEvent, 'Expected TextRecognizedEvent instance');
 		$this->assertEquals('[OCR skipped on page(s) 1]', trim($textRecognizedEvent->getRecognizedText()), 'Expected recognized text');
 	}
+
+	public function testWorkflowOcrLocalBackendPngWithAlphaChannel(): void {
+		$this->addOperation('image/png');
+		$this->uploadTestFile('png-with-alpha-channel.png');
+		$this->runOcrBackgroundJob();
+
+		$this->assertEmpty($this->apiClient->getRequests(), 'Expected no OCR Backend Service requests');
+		$this->assertEquals(1, count($this->capturedEvents), 'Expected 1 TextRecognizedEvent');
+		$textRecognizedEvent = $this->capturedEvents[0];
+		$this->assertInstanceOf(TextRecognizedEvent::class, $textRecognizedEvent, 'Expected TextRecognizedEvent instance');
+		$this->assertEquals('PNG with alpha channel', trim($textRecognizedEvent->getRecognizedText()), 'Expected recognized text');
+	}
+
+	public function testWorkflowOcrLocalBackendRegularJpg(): void {
+		$this->addOperation('image/png');
+		$this->uploadTestFile('png-without-alpha-channel.png');
+		$this->runOcrBackgroundJob();
+
+		$this->assertEmpty($this->apiClient->getRequests(), 'Expected no OCR Backend Service requests');
+		$this->assertEquals(1, count($this->capturedEvents), 'Expected 1 TextRecognizedEvent');
+		$textRecognizedEvent = $this->capturedEvents[0];
+		$this->assertInstanceOf(TextRecognizedEvent::class, $textRecognizedEvent, 'Expected TextRecognizedEvent instance');
+		$this->assertEquals('PNG without alpha channel', trim($textRecognizedEvent->getRecognizedText()), 'Expected recognized text');
+	}
 }
diff --git a/tests/Integration/testdata/png-with-alpha-channel.png b/tests/Integration/testdata/png-with-alpha-channel.png
new file mode 100644
index 00000000..194d8910
Binary files /dev/null and b/tests/Integration/testdata/png-with-alpha-channel.png differ
diff --git a/tests/Integration/testdata/png-without-alpha-channel.png b/tests/Integration/testdata/png-without-alpha-channel.png
new file mode 100644
index 00000000..9ca984c6
Binary files /dev/null and b/tests/Integration/testdata/png-without-alpha-channel.png differ
diff --git a/tests/Unit/OcrProcessors/Local/ImageOcrProcessorTest.php b/tests/Unit/OcrProcessors/Local/ImageOcrProcessorTest.php
index 46a9a4c6..df34c3c7 100644
--- a/tests/Unit/OcrProcessors/Local/ImageOcrProcessorTest.php
+++ b/tests/Unit/OcrProcessors/Local/ImageOcrProcessorTest.php
@@ -35,6 +35,8 @@
 use Test\TestCase;
 
 class ImageOcrProcessorTest extends TestCase {
+	/** @var \OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions|MockObject */
+	private $phpNative;
 	public function testOcrFileSetsImageDpi() {
 		/** @var ICommand|MockObject $command */
 		$command = $this->createMock(ICommand::class);
@@ -49,11 +51,22 @@ public function testOcrFileSetsImageDpi() {
 		$commandLineUtils->method('getCommandlineArgs')
 			->willReturnCallback(fn ($settings, $globalSettings, $sidecarFile, $additionalCommandlineArgs) => implode(' ', $additionalCommandlineArgs));
 
-		$processor = new ImageOcrProcessor($command, $logger, $sidecarFileAccessor, $commandLineUtils);
+		$phpNative = $this->createMock(\OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions::class);
+		$phpNative->method('fopen')->willReturnCallback(fn ($file, $mode) => fopen($file, $mode));
+		$phpNative->method('streamGetContents')->willReturnCallback(fn ($h) => stream_get_contents($h));
 
+		$processor = new ImageOcrProcessor($command, $logger, $sidecarFileAccessor, $commandLineUtils, $phpNative);
+
+		$file->method('fopen')
+			->willReturnCallback(function ($mode) {
+				$stream = fopen('php://temp', 'r+');
+				fwrite($stream, 'content');
+				rewind($stream);
+				return $stream;
+			});
 		$file->expects($this->once())
-			->method('getContent')
-			->willReturn('content');
+			->method('getName')
+			->willReturn('test.pdf');
 		$command->expects($this->once())
 			->method('setCommand')
 			->with($this->stringContains(' --image-dpi 300 '))
diff --git a/tests/Unit/OcrProcessors/Local/PdfOcrProcessorTest.php b/tests/Unit/OcrProcessors/Local/PdfOcrProcessorTest.php
index bdade24a..c7cff0df 100644
--- a/tests/Unit/OcrProcessors/Local/PdfOcrProcessorTest.php
+++ b/tests/Unit/OcrProcessors/Local/PdfOcrProcessorTest.php
@@ -64,6 +64,8 @@ class PdfOcrProcessorTest extends TestCase {
 	private $defaultSettings;
 	/** @var GlobalSettings */
 	private $defaultGlobalSettings;
+	/** @var \OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions|MockObject */
+	private $phpNative;
 
 	protected function setUp(): void {
 		parent::setUp();
@@ -82,6 +84,15 @@ protected function setUp(): void {
 			->willReturn(self::FILE_CONTENT_BEFORE);
 		$this->fileBefore->method('getMimeType')
 			->willReturnCallback(fn () => $this->fileBeforeMimeType);
+		$this->fileBefore->method('getName')
+			->willReturn('someFileName.pdf');
+		$this->fileBefore->method('fopen')
+			->willReturnCallback(function ($mode) {
+				$stream = fopen('php://temp', 'r+');
+				fwrite($stream, self::FILE_CONTENT_BEFORE);
+				rewind($stream);
+				return $stream;
+			});
 
 		$this->fileBeforeMimeType = 'application/pdf';
 		$this->ocrMyPdfOutput = self::FILE_CONTENT_AFTER;
@@ -90,6 +101,14 @@ protected function setUp(): void {
 		;
 		$this->ocrBackendInfoService->method('isRemoteBackend')
 			->willReturn(false);
+
+		$this->phpNative = $this->createMock(\OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions::class);
+		$this->phpNative->method('fopen')->willReturnCallback(function ($file, $mode) {
+			return fopen($file, $mode);
+		});
+		$this->phpNative->method('streamGetContents')->willReturnCallback(function ($h) {
+			return stream_get_contents($h);
+		});
 	}
 
 	public function testCallsCommandInterface() {
@@ -103,7 +122,7 @@ public function testCallsCommandInterface() {
 			->method('execute')
 			->willReturn(true);
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$result = $processor->ocrFile($this->fileBefore, $this->defaultSettings, $this->defaultGlobalSettings);
 
 		$this->assertEquals(self::FILE_CONTENT_AFTER, $result->getFileContent());
@@ -123,7 +142,7 @@ public function testThrowsOcrNotPossibleException() {
 		$this->command->expects($this->once())
 			->method('getExitCode');
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$thrown = false;
 
 		try {
@@ -162,7 +181,7 @@ public function testLogsWarningIfOcrMyPdfSucceedsWithWarningOutput() {
 							&& $paramsArray['errorOutput'] === 'getErrorOutput';
 				}));
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$processor->ocrFile($this->fileBefore, $this->defaultSettings, $this->defaultGlobalSettings);
 	}
 
@@ -177,19 +196,16 @@ public function testThrowsErrorIfOcrFileWasEmpty() {
 			->method('getStdErr')
 			->willReturn('stdErr');
 		$this->ocrMyPdfOutput = '';
-		$this->fileBefore->expects($this->once())
-			->method('getPath')
-			->willReturn('/admin/files/somefile.pdf');
 
 		$thrown = false;
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 
 		try {
 			$processor->ocrFile($this->fileBefore, $this->defaultSettings, $this->defaultGlobalSettings);
 		} catch (\Throwable $t) {
 			$thrown = true;
 			$this->assertInstanceOf(OcrResultEmptyException::class, $t);
-			$this->assertEquals('OCRmyPDF did not produce any output for file /admin/files/somefile.pdf', $t->getMessage());
+			$this->assertEquals('OCRmyPDF did not produce any output for file someFileName.pdf', $t->getMessage());
 		}
 
 		$this->assertTrue($thrown);
@@ -206,7 +222,7 @@ public function testLanguageSettingsAreSetCorrectly() {
 			->method('getOutput')
 			->willReturn('someOcrContent');
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$processor->ocrFile($this->fileBefore, new WorkflowSettings('{"languages": ["deu", "eng"] }'), $this->defaultGlobalSettings);
 	}
 
@@ -221,7 +237,7 @@ public function testRemoveBackgroundFlagIsSetCorrectly() {
 			->method('getOutput')
 			->willReturn('someOcrContent');
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$processor->ocrFile($this->fileBefore, new WorkflowSettings('{"removeBackground": true }'), $this->defaultGlobalSettings);
 	}
 
@@ -236,7 +252,7 @@ public function testProcessorCountIsNotSetIfGlobalSettingsDoesNotContainProcesso
 			->method('getOutput')
 			->willReturn('someOcrContent');
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$processor->ocrFile($this->fileBefore, $this->defaultSettings, $this->defaultGlobalSettings);
 	}
 
@@ -253,7 +269,7 @@ public function testProcessorCountIsSetCorrectlyFromGobalSettings() {
 
 		$this->defaultGlobalSettings->processorCount = 42;
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$processor->ocrFile($this->fileBefore, $this->defaultSettings, $this->defaultGlobalSettings);
 	}
 
@@ -271,10 +287,10 @@ public function testLogsInfoIfSidecarFileContentWasEmpty() {
 		$this->logger->expects($this->once())
 			->method('info')
 			->with($this->callback(function ($message) {
-				return strpos($message, 'Temporary sidecar file at') !== false && strpos($message, 'was empty') !== false;
+				return $message === 'Recognized text was empty';
 			}));
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$processor->ocrFile($this->fileBefore, $this->defaultSettings, $this->defaultGlobalSettings);
 	}
 
@@ -292,7 +308,7 @@ public function testDoesNotLogInfoIfSidecarFileContentWasNotEmpty() {
 		$this->logger->expects($this->never())
 			->method('info');
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$processor->ocrFile($this->fileBefore, $this->defaultSettings, $this->defaultGlobalSettings);
 	}
 
@@ -313,7 +329,7 @@ public function testAppliesSidecarParameterIfSidecarFileCanBeCreated() {
 			->method('getOrCreateSidecarFile')
 			->willReturn('/tmp/sidecar.txt');
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$processor->ocrFile($this->fileBefore, $this->defaultSettings, $this->defaultGlobalSettings);
 	}
 
@@ -335,7 +351,7 @@ public function testAppliesOcrModeParameter(int $simulatedOcrMode, string $expec
 			->method('getOrCreateSidecarFile')
 			->willReturn('/tmp/sidecar.txt');
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$processor->ocrFile($this->fileBefore, new WorkflowSettings('{"ocrMode": ' . $simulatedOcrMode . '}'), $this->defaultGlobalSettings);
 	}
 
@@ -361,7 +377,7 @@ public function testRemoveBackgroundIsNotAppliedIfOcrModeIsRedoOcr() {
 				return strpos($message, '--remove-background is incompatible with --redo-ocr') !== false;
 			}));
 
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$processor->ocrFile($this->fileBefore, new WorkflowSettings('{"ocrMode": ' . WorkflowSettings::OCR_MODE_REDO_OCR . ', "removeBackground": true}'), $this->defaultGlobalSettings);
 	}
 
@@ -383,7 +399,7 @@ public function testAppliesCustomCliArgsCorrectly() {
 			->willReturn('/tmp/sidecar.txt');
 
 		$workflowSettings = new WorkflowSettings('{"customCliArgs": "--output-type pdf"}');
-		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+		$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 		$processor->ocrFile($this->fileBefore, $workflowSettings, $this->defaultGlobalSettings);
 	}
 
@@ -406,7 +422,7 @@ public function testThrowsOcrAlreadyDoneExceptionIfErrorCodeIsEquals6() {
 
 		$thrown = false;
 		try {
-			$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils);
+			$processor = new PdfOcrProcessor($this->command, $this->logger, $this->sidecarFileAccessor, $this->commandLineUtils, $this->phpNative);
 			$processor->ocrFile($this->fileBefore, $this->defaultSettings, $this->defaultGlobalSettings);
 		} catch (\Throwable $t) {
 			$thrown = true;
diff --git a/tests/Unit/OcrProcessors/OcrProcessorBaseTest.php b/tests/Unit/OcrProcessors/OcrProcessorBaseTest.php
new file mode 100644
index 00000000..d09d4add
--- /dev/null
+++ b/tests/Unit/OcrProcessors/OcrProcessorBaseTest.php
@@ -0,0 +1,217 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\WorkflowOcr\Tests\Unit\OcrProcessors;
+
+use OCA\WorkflowOcr\Helper\ISidecarFileAccessor;
+use OCA\WorkflowOcr\Model\GlobalSettings;
+use OCA\WorkflowOcr\Model\WorkflowSettings;
+use OCA\WorkflowOcr\OcrProcessors\ICommandLineUtils;
+
+use OCA\WorkflowOcr\OcrProcessors\Local\OcrMyPdfBasedProcessor;
+use OCA\WorkflowOcr\OcrProcessors\OcrProcessorBase;
+use OCA\WorkflowOcr\Wrapper\ICommand;
+use OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions;
+use OCP\Files\File;
+use PHPUnit\Framework\TestCase;
+use Psr\Log\LoggerInterface;
+
+class BadReadStreamWrapper {
+	public $context;
+	public function stream_open($path, $mode, $options, &$opened_path) {
+		return true;
+	}
+
+	public function stream_read($count) {
+		return false; // simulate read failure
+	}
+
+	public function stream_eof() {
+		return false; // not EOF, so read failure is treated as a read error
+	}
+
+	public function stream_stat() {
+		return false;
+	}
+}
+
+class TestOcrProcessor extends OcrProcessorBase {
+	public function __construct($logger, IPhpNativeFunctions $phpNative) {
+		parent::__construct($logger, $phpNative);
+	}
+
+	protected function doOcrProcessing($fileResource, string $fileName, $settings, $globalSettings): array {
+		// Return the preprocessed file bytes so tests can inspect preprocessing result
+		$contents = '';
+		if (is_resource($fileResource)) {
+			rewind($fileResource);
+			$contents = stream_get_contents($fileResource);
+		}
+		return [true, $contents, 'recognized', 0, ''];
+	}
+}
+
+class TestableOcrMyPdfBasedProcessor extends OcrMyPdfBasedProcessor {
+	public function __construct($command, $logger, $sidecar, $cmdUtils, $phpNative) {
+		parent::__construct($command, $logger, $sidecar, $cmdUtils, $phpNative);
+	}
+
+	public function runCallToDoOcrProcessing($fileResource, string $fileName, $settings, $globalSettings): array {
+		return $this->doOcrProcessing($fileResource, $fileName, $settings, $globalSettings);
+	}
+
+	protected function getAdditionalCommandlineArgs($settings, $globalSettings): array {
+		return [];
+	}
+}
+
+class OcrProcessorBaseTest extends TestCase {
+	public function testRemoveAlphaChannelFromImage_RemovesAlphaAndReturnsNewStream(): void {
+		$logger = $this->createMock(LoggerInterface::class);
+		$phpNative = $this->createMock(IPhpNativeFunctions::class);
+		$phpNative->method('fopen')->willReturnCallback(fn ($file, $mode) => fopen($file, $mode));
+		$phpNative->method('streamGetContents')->willReturnCallback(fn ($h) => stream_get_contents($h));
+
+		$processor = new TestOcrProcessor($logger, $phpNative);
+
+		$originalStream = $this->createPngStream(true);
+
+		$file = $this->createMock(File::class);
+		$file->method('getMimeType')->willReturn('image/png');
+		$file->method('fopen')->with('rb')->willReturn($originalStream);
+		$file->method('getName')->willReturn('test.png');
+
+		$settings = $this->createMock(WorkflowSettings::class);
+		$globalSettings = $this->createMock(GlobalSettings::class);
+
+		// Capture original bytes before ocrFile closes streams
+		if (!is_resource($originalStream)) {
+			$this->fail('createPngStream did not return a valid stream resource');
+		}
+		$originalBytes = stream_get_contents($originalStream);
+		rewind($originalStream);
+
+		$result = $processor->ocrFile($file, $settings, $globalSettings);
+
+		$this->assertNotNull($result);
+		$processed = $result->getFileContent();
+
+		// Check PNG IHDR color type byte: 6 = RGBA (has alpha), 2 = RGB (no alpha)
+		$this->assertGreaterThanOrEqual(26, strlen($originalBytes), 'PNG too short to inspect IHDR');
+		$origColorType = ord($originalBytes[25]);
+		$procColorType = ord($processed[25]);
+
+		$this->assertEquals(6, $origColorType, 'Original should have RGBA color type');
+		$this->assertNotEquals(6, $procColorType, 'Processed image should not have RGBA color type');
+	}
+
+	public function testDoOcrProcessingReturnsErrorIfInputFileCannotBeRead(): void {
+		$logger = $this->createMock(LoggerInterface::class);
+
+		// Create mocks for constructor dependencies
+		$command = $this->createMock(ICommand::class);
+		$sidecar = $this->createMock(ISidecarFileAccessor::class);
+		$cmdUtils = $this->createMock(ICommandLineUtils::class);
+		$phpNative = $this->createMock(IPhpNativeFunctions::class);
+
+		// Mock that "stream_get_contents" fails
+		$phpNative->method('streamGetContents')->willReturn(false);
+
+		$processor = new TestableOcrMyPdfBasedProcessor($command, $logger, $sidecar, $cmdUtils, $phpNative);
+
+		$settings = $this->createMock(WorkflowSettings::class);
+		$globalSettings = $this->createMock(GlobalSettings::class);
+
+		$badStream = fopen('php://temp', 'r');
+		try {
+			$result = $processor->runCallToDoOcrProcessing($badStream, 'unreadable.pdf', $settings, $globalSettings);
+		} finally {
+			if (is_resource($badStream)) {
+				fclose($badStream);
+			}
+		}
+
+		$this->assertIsArray($result);
+		$this->assertFalse($result[0], 'Expected processing to indicate failure');
+		$this->assertSame(-1, $result[3], 'Expected exit code -1 for read failure');
+		$this->assertStringContainsString('Failed to read file content', (string)$result[4]);
+	}
+
+	public function testRemoveAlphaChannelFromImage_NoAlpha_ReturnsOriginalResource(): void {
+		$logger = $this->createMock(LoggerInterface::class);
+		$phpNative = $this->createMock(IPhpNativeFunctions::class);
+		$phpNative->method('fopen')->willReturnCallback(fn ($file, $mode) => fopen($file, $mode));
+		$phpNative->method('streamGetContents')->willReturnCallback(fn ($h) => stream_get_contents($h));
+
+		$processor = new TestOcrProcessor($logger, $phpNative);
+
+		$originalStream = $this->createPngStream(false);
+
+		$file = $this->createMock(File::class);
+		$file->method('getMimeType')->willReturn('image/png');
+		$file->method('fopen')->with('rb')->willReturn($originalStream);
+		$file->method('getName')->willReturn('test_no_alpha.png');
+
+		$settings = $this->createMock(WorkflowSettings::class);
+		$globalSettings = $this->createMock(GlobalSettings::class);
+
+		// Capture original bytes before ocrFile closes streams
+		rewind($originalStream);
+		$originalBytes = stream_get_contents($originalStream);
+		rewind($originalStream);
+
+		$result = $processor->ocrFile($file, $settings, $globalSettings);
+
+		$this->assertNotNull($result);
+		$processed = $result->getFileContent();
+
+		// For no-alpha images the preprocessed bytes should equal the original
+		$this->assertEquals($originalBytes, $processed);
+	}
+
+	public function testThrowsRuntimeExceptionIfOpeningTempFails(): void {
+		$logger = $this->createMock(LoggerInterface::class);
+		$phpNative = $this->createMock(IPhpNativeFunctions::class);
+
+		// Simulate failure when opening the temporary stream for alpha removal
+		$phpNative->method('fopen')->with('php://temp', 'r+')->willReturn(false);
+
+		$processor = new TestOcrProcessor($logger, $phpNative);
+
+		$originalStream = $this->createPngStream(true);
+
+		$file = $this->createMock(File::class);
+		$file->method('getMimeType')->willReturn('image/png');
+		$file->method('fopen')->with('rb')->willReturn($originalStream);
+		$file->method('getName')->willReturn('test.png');
+
+		$settings = $this->createMock(WorkflowSettings::class);
+		$globalSettings = $this->createMock(GlobalSettings::class);
+
+		$this->expectException(\RuntimeException::class);
+		$this->expectExceptionMessage('Failed to create temporary stream for alpha channel removal');
+
+		$processor->ocrFile($file, $settings, $globalSettings);
+	}
+
+	private function createPngStream(bool $withAlpha) {
+		$stream = fopen('php://temp', 'r+');
+		$img = imagecreatetruecolor(10, 10);
+		if ($withAlpha) {
+			imagesavealpha($img, true);
+			$trans_colour = imagecolorallocatealpha($img, 0, 0, 0, 127);
+			imagefill($img, 0, 0, $trans_colour);
+		} else {
+			$white = imagecolorallocate($img, 255, 255, 255);
+			imagefill($img, 0, 0, $white);
+		}
+		ob_start();
+		imagepng($img);
+		$png = ob_get_clean();
+		imagedestroy($img);
+		fwrite($stream, $png);
+		rewind($stream);
+		return $stream;
+	}
+}
diff --git a/tests/Unit/OcrProcessors/Remote/WorkflowOcrRemoteProcessorTest.php b/tests/Unit/OcrProcessors/Remote/WorkflowOcrRemoteProcessorTest.php
index d478d0a2..9e69a56a 100644
--- a/tests/Unit/OcrProcessors/Remote/WorkflowOcrRemoteProcessorTest.php
+++ b/tests/Unit/OcrProcessors/Remote/WorkflowOcrRemoteProcessorTest.php
@@ -46,6 +46,8 @@ class WorkflowOcrRemoteProcessorTest extends TestCase {
 	private $workflowSettings;
 	private $globalSettings;
 	private $processor;
+	/** @var \OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions|MockObject */
+	private $phpNative;
 
 	protected function setUp(): void {
 		$this->apiClient = $this->createMock(IApiClient::class);
@@ -55,10 +57,13 @@ protected function setUp(): void {
 		$this->workflowSettings = $this->createMock(WorkflowSettings::class);
 		$this->globalSettings = $this->createMock(GlobalSettings::class);
 
+		$this->phpNative = $this->createMock(\OCA\WorkflowOcr\Wrapper\IPhpNativeFunctions::class);
+
 		$this->processor = new WorkflowOcrRemoteProcessor(
 			$this->apiClient,
 			$this->commandLineUtils,
-			$this->logger
+			$this->logger,
+			$this->phpNative
 		);
 	}
 
@@ -85,7 +90,6 @@ public function testOcrFileSuccess(): void {
 
 		$this->assertInstanceOf(OcrProcessorResult::class, $result);
 		$this->assertEquals('file content', $result->getFileContent());
-		$this->assertEquals('pdf', $result->getFileExtension());
 		$this->assertEquals('recognized text', $result->getRecognizedText());
 	}
 
diff --git a/tests/Unit/Service/EventServiceTest.php b/tests/Unit/Service/EventServiceTest.php
index a9925e84..9c676f8b 100644
--- a/tests/Unit/Service/EventServiceTest.php
+++ b/tests/Unit/Service/EventServiceTest.php
@@ -48,7 +48,7 @@ public function testTextRecognizedDispatchesEvent() {
 		/** @var File|MockObject */
 		$file = $this->createMock(File::class);
 		$recognizedText = 'recognizedText';
-		$ocrResult = new OcrProcessorResult('content', 'pdf', $recognizedText);
+		$ocrResult = new OcrProcessorResult('content', $recognizedText);
 		$this->eventDispatcher->expects($this->once())
 			->method('dispatchTyped')
 			->with($this->callback(function (TextRecognizedEvent $event) use ($recognizedText, $file) {
diff --git a/tests/Unit/Service/OcrServiceTest.php b/tests/Unit/Service/OcrServiceTest.php
index 1b0d1d4b..6e99e7f6 100644
--- a/tests/Unit/Service/OcrServiceTest.php
+++ b/tests/Unit/Service/OcrServiceTest.php
@@ -382,7 +382,7 @@ public function testCreatesNewFileVersionAndEmitsTextRecognizedEvent(string $ori
 		$mimeType = 'application/pdf';
 		$content = 'someFileContent';
 		$ocrContent = 'someOcrProcessedFile';
-		$ocrResult = new OcrProcessorResult($ocrContent, 'pdf', $ocrContent); // Extend this cases if we add new OCR processors
+		$ocrResult = new OcrProcessorResult($ocrContent, $ocrContent); // Extend this cases if we add new OCR processors
 		$originalFileMock = $this->createValidFileMock($mimeType, $content, $rootFolderPath, $originalFilename);
 
 		$this->rootFolderGetFirstNodeById42ReturnValue = $originalFileMock;
@@ -472,7 +472,7 @@ public function testCallsProcessingFileAccessor() {
 		$content = 'someFileContent';
 		$ocrContent = 'someOcrProcessedFile';
 		$filePath = '/admin/files/somefile.pdf';
-		$ocrResult = new OcrProcessorResult($ocrContent, 'pdf', $ocrContent); // Extend this cases if we add new OCR processors
+		$ocrResult = new OcrProcessorResult($ocrContent, $ocrContent); // Extend this cases if we add new OCR processors
 
 		$this->rootFolderGetFirstNodeById42ReturnValue = $this->createValidFileMock($mimeType, $content);
 
@@ -515,7 +515,7 @@ public function testDoesNotCreateNewFileVersionIfOcrContentWasEmpty() {
 		$mimeType = 'application/pdf';
 		$content = 'someFileContent';
 		$ocrContent = '';
-		$ocrResult = new OcrProcessorResult($ocrContent, 'pdf', $ocrContent);
+		$ocrResult = new OcrProcessorResult($ocrContent, $ocrContent);
 		$fileId = 42;
 
 		$this->rootFolder->expects($this->never())->method('getById');
@@ -600,7 +600,7 @@ public function testRestoreOriginalFileModificationDate() {
 		$mimeType = 'application/pdf';
 		$content = 'someFileContent';
 		$ocrContent = 'someOcrProcessedFile';
-		$ocrResult = new OcrProcessorResult($ocrContent, 'pdf', $ocrContent); // Extend this cases if we add new OCR processors
+		$ocrResult = new OcrProcessorResult($ocrContent, $ocrContent); // Extend this cases if we add new OCR processors
 
 		$fileMock = $this->createValidFileMock($mimeType, $content);
 		$this->rootFolderGetFirstNodeById42ReturnValue = $fileMock;
@@ -682,7 +682,7 @@ public function testCreatesNewFileVersionWithSuffixIfNodeIsNotUpdateable() {
 		$mimeType = 'application/pdf';
 		$content = 'someFileContent';
 		$ocrContent = 'someOcrProcessedFile';
-		$ocrResult = new OcrProcessorResult($ocrContent, 'pdf', $ocrContent); // Extend this cases if we add new OCR processors
+		$ocrResult = new OcrProcessorResult($ocrContent, $ocrContent); // Extend this cases if we add new OCR processors
 
 		$fileMock = $this->createValidFileMock($mimeType, $content, '/admin/files', 'somefile.pdf', false);
 		$this->rootFolderGetFirstNodeById42ReturnValue = $fileMock;
diff --git a/tests/psalm-baseline.xml b/tests/psalm-baseline.xml
index 34c1c659..ff0eaae0 100644
--- a/tests/psalm-baseline.xml
+++ b/tests/psalm-baseline.xml
@@ -155,6 +155,7 @@
     <PossiblyUnusedMethod>
       <code><![CDATA[__construct]]></code>
       <code><![CDATA[getContentType]]></code>
+      <code><![CDATA[getFilename]]></code>
       <code><![CDATA[setContentType]]></code>
       <code><![CDATA[setFileContent]]></code>
       <code><![CDATA[setFilename]]></code>