optimize batch generation of previews

by allowing the generation of multiple previews at once we save on having to find, open and decode the max-preview for every preview of the same file

the main use case for this is the preview generator app (pr for that comming next)

in my local testing this saves about 25% of time when using the preview generator app

Signed-off-by: Robin Appelman <robin@icewind.nl>

3 files changed, 144 insertions, 15 deletions

diff --git a/lib/private/Preview/Generator.php b/lib/private/Preview/Generator.php
index 073001d6788..eedf80d8522 100644
--- a/lib/private/Preview/Generator.php
+++ b/lib/private/Preview/Generator.php
@@ -138,6 +138,7 @@ class Generator {
 
 		// Get the max preview and infer the max preview sizes from that
 		$maxPreview = $this->getMaxPreview($previewFolder, $file, $mimeType, $previewVersion);
+		$maxPreviewImage = null; // only load the image when we need it
 		if ($maxPreview->getSize() === 0) {
 			$maxPreview->delete();
 			throw new NotFoundException('Max preview size 0, invalid!');
@@ -174,7 +175,11 @@ class Generator {
 				try {
 					$preview = $this->getCachedPreview($previewFolder, $width, $height, $crop, $maxPreview->getMimeType(), $previewVersion);
 				} catch (NotFoundException $e) {
-					$preview = $this->generatePreview($previewFolder, $maxPreview, $width, $height, $crop, $maxWidth, $maxHeight, $previewVersion);
+					if ($maxPreviewImage === null) {
+						$maxPreviewImage = $this->helper->getImage($maxPreview);
+					}
+
+					$preview = $this->generatePreview($previewFolder, $maxPreviewImage, $width, $height, $crop, $maxWidth, $maxHeight, $previewVersion);
 				}
 			} catch (\InvalidArgumentException $e) {
 				throw new NotFoundException();
@@ -386,9 +391,8 @@ class Generator {
 	 * @throws NotFoundException
 	 * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
 	 */
-	private function generatePreview(ISimpleFolder $previewFolder, ISimpleFile $maxPreview, $width, $height, $crop, $maxWidth, $maxHeight, $prefix) {
-		$preview = $this->helper->getImage($maxPreview);
-
+	private function generatePreview(ISimpleFolder $previewFolder, IImage $maxPreview, $width, $height, $crop, $maxWidth, $maxHeight, $prefix) {
+		$preview = $maxPreview;
 		if (!$preview->valid()) {
 			throw new \InvalidArgumentException('Failed to generate preview, failed to load image');
 		}
@@ -406,13 +410,13 @@ class Generator {
 					$scaleH = $maxHeight / $widthR;
 					$scaleW = $width;
 				}
-				$preview->preciseResize((int)round($scaleW), (int)round($scaleH));
+				$preview = $preview->preciseResizeCopy((int)round($scaleW), (int)round($scaleH));
 			}
 			$cropX = (int)floor(abs($width - $preview->width()) * 0.5);
 			$cropY = (int)floor(abs($height - $preview->height()) * 0.5);
-			$preview->crop($cropX, $cropY, $width, $height);
+			$preview = $preview->cropCopy($cropX, $cropY, $width, $height);
 		} else {
-			$preview->resize(max($width, $height));
+			$preview = $maxPreview->resizeCopy(max($width, $height));
 		}
 
 
diff --git a/lib/private/legacy/OC_Image.php b/lib/private/legacy/OC_Image.php
index 7d23ece7ffa..73d380eb99a 100644
--- a/lib/private/legacy/OC_Image.php
+++ b/lib/private/legacy/OC_Image.php
@@ -39,6 +39,8 @@
  *
  */
 
+use OCP\IImage;
+
 /**
  * Class for basic image manipulation
  */
@@ -845,6 +847,17 @@ class OC_Image implements \OCP\IImage {
 	 * @return bool
 	 */
 	public function resize($maxSize) {
+		$result = $this->resizeNew($maxSize);
+		imagedestroy($this->resource);
+		$this->resource = $result;
+		return is_resource($result);
+	}
+
+	/**
+	 * @param $maxSize
+	 * @return resource | bool
+	 */
+	private function resizeNew($maxSize) {
 		if (!$this->valid()) {
 			$this->logger->error(__METHOD__ . '(): No image loaded', ['app' => 'core']);
 			return false;
@@ -861,8 +874,7 @@ class OC_Image implements \OCP\IImage {
 			$newHeight = $maxSize;
 		}
 
-		$this->preciseResize((int)round($newWidth), (int)round($newHeight));
-		return true;
+		return $this->preciseResizeNew((int)round($newWidth), (int)round($newHeight));
 	}
 
 	/**
@@ -871,6 +883,19 @@ class OC_Image implements \OCP\IImage {
 	 * @return bool
 	 */
 	public function preciseResize(int $width, int $height): bool {
+		$result = $this->preciseResizeNew($width, $height);
+		imagedestroy($this->resource);
+		$this->resource = $result;
+		return is_resource($result);
+	}
+
+
+	/**
+	 * @param int $width
+	 * @param int $height
+	 * @return resource | bool
+	 */
+	public function preciseResizeNew(int $width, int $height) {
 		if (!$this->valid()) {
 			$this->logger->error(__METHOD__ . '(): No image loaded', ['app' => 'core']);
 			return false;
@@ -896,9 +921,7 @@ class OC_Image implements \OCP\IImage {
 			imagedestroy($process);
 			return false;
 		}
-		imagedestroy($this->resource);
-		$this->resource = $process;
-		return true;
+		return $process;
 	}
 
 	/**
@@ -969,6 +992,22 @@ class OC_Image implements \OCP\IImage {
 	 * @return bool for success or failure
 	 */
 	public function crop(int $x, int $y, int $w, int $h): bool {
+		$result = $this->cropNew($x, $y, $w, $h);
+		imagedestroy($this->resource);
+		$this->resource = $result;
+		return is_resource($result);
+	}
+
+	/**
+	 * Crops the image from point $x$y with dimension $wx$h.
+	 *
+	 * @param int $x Horizontal position
+	 * @param int $y Vertical position
+	 * @param int $w Width
+	 * @param int $h Height
+	 * @return resource | bool
+	 */
+	public function cropNew(int $x, int $y, int $w, int $h) {
 		if (!$this->valid()) {
 			$this->logger->error(__METHOD__ . '(): No image loaded', ['app' => 'core']);
 			return false;
@@ -993,9 +1032,7 @@ class OC_Image implements \OCP\IImage {
 			imagedestroy($process);
 			return false;
 		}
-		imagedestroy($this->resource);
-		$this->resource = $process;
-		return true;
+		return $process;
 	}
 
 	/**
@@ -1045,6 +1082,55 @@ class OC_Image implements \OCP\IImage {
 		return false;
 	}
 
+	public function copy(): IImage {
+		$image = new OC_Image(null, $this->logger, $this->config);
+		$image->resource = imagecreatetruecolor($this->width(), $this->height());
+		imagecopy(
+			$image->resource(),
+			$this->resource(),
+			0,
+			0,
+			0,
+			0,
+			$this->width(),
+			$this->height()
+		);
+
+		return $image;
+	}
+
+	public function cropCopy(int $x, int $y, int $w, int $h): IImage {
+		$image = new OC_Image(null, $this->logger, $this->config);
+		$image->resource = $this->cropNew($x, $y, $w, $h);
+
+		return $image;
+	}
+
+	public function preciseResizeCopy(int $width, int $height): IImage {
+		$image = new OC_Image(null, $this->logger, $this->config);
+		$image->resource = $this->preciseResizeNew($width, $height);
+
+		return $image;
+	}
+
+	public function resizeCopy(int $maxSize): IImage {
+		$image = new OC_Image(null, $this->logger, $this->config);
+		$image->resource = $this->resizeNew($maxSize);
+
+		return $image;
+	}
+
+
+	/**
+	 * Resizes the image preserving ratio, returning a new copy
+	 *
+	 * @param integer $maxSize The maximum size of either the width or height.
+	 * @return bool
+	 */
+	public function copyResize($maxSize): IImage {
+
+	}
+
 	/**
 	 * Destroys the current image and resets the object
 	 */
diff --git a/lib/public/IImage.php b/lib/public/IImage.php
index 67db6b097ef..6e6c28609d8 100644
--- a/lib/public/IImage.php
+++ b/lib/public/IImage.php
@@ -190,4 +190,43 @@ interface IImage {
 	 * @since 8.1.0
 	 */
 	public function scaleDownToFit($maxWidth, $maxHeight);
+
+	/**
+	 * create a copy of this image
+	 *
+	 * @return IImage
+	 * @since 19.0.0
+	 */
+	public function copy(): IImage;
+
+	/**
+	 * create a new cropped copy of this image
+	 *
+	 * @param int $x Horizontal position
+	 * @param int $y Vertical position
+	 * @param int $w Width
+	 * @param int $h Height
+	 * @return IImage
+	 * @since 19.0.0
+	 */
+	public function cropCopy(int $x, int $y, int $w, int $h): IImage;
+
+	/**
+	 * create a new resized copy of this image
+	 *
+	 * @param int $width
+	 * @param int $height
+	 * @return IImage
+	 * @since 19.0.0
+	 */
+	public function preciseResizeCopy(int $width, int $height): IImage;
+
+	/**
+	 * create a new resized copy of this image
+	 *
+	 * @param integer $maxSize The maximum size of either the width or height.
+	 * @return IImage
+	 * @since 19.0.0
+	 */
+	public function resizeCopy(int $maxSize): IImage;
 }