Avoid memory leak by releasing image resources

This also better support image cloning with a proper
clone of the GD resource.

#2092

phpstan-baseline.neon

@@ -5920,16 +5920,6 @@ parameters:
 			count: 1
 			path: src/PhpSpreadsheet/Worksheet/Iterator.php
 
-		-
-			message: "#^Parameter \\#1 \\$im of function imagesx expects resource, GdImage\\|resource given\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Worksheet/MemoryDrawing.php
-
-		-
-			message: "#^Parameter \\#1 \\$im of function imagesy expects resource, GdImage\\|resource given\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Worksheet/MemoryDrawing.php
-
 		-
 			message: "#^Property PhpOffice\\\\PhpSpreadsheet\\\\Worksheet\\\\PageSetup\\:\\:\\$pageOrder has no typehint specified\\.$#"
 			count: 1

phpstan.neon.dist

@@ -16,6 +16,8 @@ parameters:
         - '~^Return typehint of method .* has invalid type GdImage\.$~'
         - '~^Property .* has unknown class GdImage as its type\.$~'
         - '~^Parameter .* of method .* has invalid typehint type GdImage\.$~'
+        - '~^Parameter \#1 \$im of function (imagedestroy|imageistruecolor|imagealphablending|imagesavealpha|imagecolortransparent|imagecolorsforindex|imagesavealpha|imagesx|imagesy) expects resource, GdImage\|resource given\.$~'
+        - '~^Parameter \#2 \$src_im of function imagecopy expects resource, GdImage\|resource given\.$~'
         # Accept a bit anything for assert methods
         - '~^Parameter \#2 .* of static method PHPUnit\\Framework\\Assert\:\:assert\w+\(\) expects .*, .* given\.$~'
         - '~^Method PhpOffice\\PhpSpreadsheetTests\\.*\:\:test.*\(\) has parameter \$args with no typehint specified\.$~'

src/PhpSpreadsheet/Worksheet/MemoryDrawing.php

@@ -3,6 +3,7 @@
 namespace PhpOffice\PhpSpreadsheet\Worksheet;
 
 use GdImage;
+use PhpOffice\PhpSpreadsheet\Exception;
 
 class MemoryDrawing extends BaseDrawing
 {
@@ -21,7 +22,7 @@ class MemoryDrawing extends BaseDrawing
     /**
      * Image resource.
      *
-     * @var GdImage|resource
+     * @var null|GdImage|resource
      */
     private $imageResource;
 
@@ -60,10 +61,71 @@ class MemoryDrawing extends BaseDrawing
         parent::__construct();
     }
 
+    public function __destruct()
+    {
+        if ($this->imageResource) {
+            imagedestroy($this->imageResource);
+            $this->imageResource = null;
+        }
+    }
+
+    public function __clone()
+    {
+        parent::__clone();
+        $this->cloneResource();
+    }
+
+    private function cloneResource(): void
+    {
+        if (!$this->imageResource) {
+            return;
+        }
+
+        $width = imagesx($this->imageResource);
+        $height = imagesy($this->imageResource);
+
+        if (imageistruecolor($this->imageResource)) {
+            $clone = imagecreatetruecolor($width, $height);
+            if (!$clone) {
+                throw new Exception('Could not clone image resource');
+            }
+
+            imagealphablending($clone, false);
+            imagesavealpha($clone, true);
+        } else {
+            $clone = imagecreate($width, $height);
+            if (!$clone) {
+                throw new Exception('Could not clone image resource');
+            }
+
+            // If the image has transparency...
+            $transparent = imagecolortransparent($this->imageResource);
+            if ($transparent >= 0) {
+                $rgb = imagecolorsforindex($this->imageResource, $transparent);
+                if ($rgb === false) {
+                    throw new Exception('Could not get image colors');
+                }
+
+                imagesavealpha($clone, true);
+                $color = imagecolorallocatealpha($clone, $rgb['red'], $rgb['green'], $rgb['blue'], $rgb['alpha']);
+                if ($color === false) {
+                    throw new Exception('Could not get image alpha color');
+                }
+
+                imagefill($clone, 0, 0, $color);
+            }
+        }
+
+        //Create the Clone!!
+        imagecopy($clone, $this->imageResource, 0, 0, 0, 0, $width, $height);
+
+        $this->imageResource = $clone;
+    }
+
     /**
      * Get image resource.
      *
-     * @return GdImage|resource
+     * @return null|GdImage|resource
      */
     public function getImageResource()
     {

src/PhpSpreadsheet/Writer/Html.php

@@ -690,18 +690,21 @@ class Html extends BaseWriter
                     $drawing->getWidth() . 'px; height: ' . $drawing->getHeight() . 'px;" src="' .
                     $imageData . '" alt="' . $filedesc . '" />';
             } elseif ($drawing instanceof MemoryDrawing) {
-                ob_start(); //  Let's start output buffering.
+                $imageResource = $drawing->getImageResource();
-                imagepng($drawing->getImageResource()); //  This will normally output the image, but because of ob_start(), it won't.
+                if ($imageResource) {
-                $contents = ob_get_contents(); //  Instead, output above is saved to $contents
+                    ob_start(); //  Let's start output buffering.
-                ob_end_clean(); //  End the output buffer.
+                    imagepng($imageResource); //  This will normally output the image, but because of ob_start(), it won't.
+                    $contents = ob_get_contents(); //  Instead, output above is saved to $contents
+                    ob_end_clean(); //  End the output buffer.
 
-                $dataUri = 'data:image/jpeg;base64,' . base64_encode($contents);
+                    $dataUri = 'data:image/jpeg;base64,' . base64_encode($contents);
 
-                //  Because of the nature of tables, width is more important than height.
+                    //  Because of the nature of tables, width is more important than height.
-                //  max-width: 100% ensures that image doesnt overflow containing cell
+                    //  max-width: 100% ensures that image doesnt overflow containing cell
-                //  width: X sets width of supplied image.
+                    //  width: X sets width of supplied image.
-                //  As a result, images bigger than cell will be contained and images smaller will not get stretched
+                    //  As a result, images bigger than cell will be contained and images smaller will not get stretched
-                $html .= '<img alt="' . $filedesc . '" src="' . $dataUri . '" style="max-width:100%;width:' . $drawing->getWidth() . 'px;" />';
+                    $html .= '<img alt="' . $filedesc . '" src="' . $dataUri . '" style="max-width:100%;width:' . $drawing->getWidth() . 'px;" />';
+                }
             }
         }