MAGETWO-84647: Handle transparncy correctly for watermark #11060

 - Merge Pull Request #11060 from elzekool/magento2:bugfix/handle-alpha-transparency-correctly-for-watermark
 - Merged commits:
   1. 92f24ec
   2. 6581e80
   3. f2446b6
   4. 519f3e1
   5. 00a5c3a
   6. 503204c

Author: Oleksii Korshenko

dev/tests/integration/testsuite/Magento/Framework/Image/Adapter/InterfaceTest.php

@@ -337,6 +337,97 @@ public function rotateDataProvider()
         );
     }
 
+    /**
+     * Test if alpha transparency is correctly handled
+     *
+     * @param string $image
+     * @param string $watermark
+     * @param int $alphaPercentage
+     * @param array $comparePoint1
+     * @param array $comparePoint2
+     * @param string $adapterType
+     *
+     * @dataProvider imageWatermarkWithAlphaTransparencyDataProvider
+     * @depends testOpen
+     * @depends testImageSize
+     */
+    public function testWatermarkWithAlphaTransparency(
+        $image,
+        $watermark,
+        $alphaPercentage,
+        $comparePoint1,
+        $comparePoint2,
+        $adapterType
+    ) {
+        $imageAdapter = $this->_getAdapter($adapterType);
+        $imageAdapter->open($image);
+
+        $watermarkAdapter = $this->_getAdapter($adapterType);
+        $watermarkAdapter->open($watermark);
+
+        list($comparePoint1X, $comparePoint1Y) = $comparePoint1;
+        list($comparePoint2X, $comparePoint2Y) = $comparePoint2;
+
+        $imageAdapter
+            ->setWatermarkImageOpacity($alphaPercentage)
+            ->setWatermarkPosition(\Magento\Framework\Image\Adapter\AbstractAdapter::POSITION_TOP_LEFT)
+            ->watermark($watermark);
+
+        $comparePoint1Color = $imageAdapter->getColorAt($comparePoint1X, $comparePoint1Y);
+        unset($comparePoint1Color['alpha']);
+
+        $comparePoint2Color = $imageAdapter->getColorAt($comparePoint2X, $comparePoint2Y);
+        unset($comparePoint2Color['alpha']);
+
+        $result = $this->_compareColors($comparePoint1Color, $comparePoint2Color);
+        $message = sprintf(
+            '%s should be different to %s due to alpha transparency',
+            join(',', $comparePoint1Color),
+            join(',', $comparePoint2Color)
+        );
+        $this->assertFalse($result, $message);
+    }
+
+    public function imageWatermarkWithAlphaTransparencyDataProvider()
+    {
+        return $this->_prepareData(
+            [
+                // Watermark with alpha channel, 25%
+                [
+                    $this->_getFixture('watermark_alpha_base_image.jpg'),
+                    $this->_getFixture('watermark_alpha.png'),
+                    25,
+                    [ 23, 3 ],
+                    [ 23, 30 ]
+                ],
+                // Watermark with alpha channel, 50%
+                [
+                    $this->_getFixture('watermark_alpha_base_image.jpg'),
+                    $this->_getFixture('watermark_alpha.png'),
+                    50,
+                    [ 23, 3 ],
+                    [ 23, 30 ]
+                ],
+                // Watermark with no alpha channel, 50%
+                [
+                    $this->_getFixture('watermark_alpha_base_image.jpg'),
+                    $this->_getFixture('watermark.png'),
+                    50,
+                    [ 3, 3 ],
+                    [ 23,3 ]
+                ],
+                // Watermark with no alpha channel, 100%
+                [
+                    $this->_getFixture('watermark_alpha_base_image.jpg'),
+                    $this->_getFixture('watermark.png'),
+                    100,
+                    [ 3, 3 ],
+                    [ 3, 60 ]
+                ],
+            ]
+        );
+    }
+
     /**
      * Checks if watermark exists on the right position
      *
@@ -350,10 +441,10 @@ public function rotateDataProvider()
      * @param int $colorY
      * @param string $adapterType
      *
-     * @dataProvider imageWatermarkDataProvider
+     * @dataProvider imageWatermarkPositionDataProvider
      * @depends testOpen
      */
-    public function testWatermark(
+    public function testWatermarkPosition(
         $image,
         $watermark,
         $width,
@@ -387,7 +478,7 @@ public function testWatermark(
         $this->assertFalse($result, $message);
     }
 
-    public function imageWatermarkDataProvider()
+    public function imageWatermarkPositionDataProvider()
     {
         return $this->_prepareData(
             [

dev/tests/integration/testsuite/Magento/Framework/Image/_files/watermark_alpha.png

@@ -5,6 +5,9 @@
  */
 namespace Magento\Framework\Image\Adapter;
 
+/**
+ * @SuppressWarnings(PHPMD.ExcessiveClassComplexity)
+ */
 class Gd2 extends \Magento\Framework\Image\Adapter\AbstractAdapter
 {
     /**
@@ -404,7 +407,7 @@ public function rotate($angle)
      */
     public function watermark($imagePath, $positionX = 0, $positionY = 0, $opacity = 30, $tile = false)
     {
-        list($watermarkSrcWidth, $watermarkSrcHeight, $watermarkFileType, ) = $this->_getImageOptions($imagePath);
+        list($watermarkSrcWidth, $watermarkSrcHeight, $watermarkFileType,) = $this->_getImageOptions($imagePath);
         $this->_getFileAttributes();
         $watermark = call_user_func(
             $this->_getCallback('create', $watermarkFileType, 'Unsupported watermark image format.'),
@@ -465,7 +468,7 @@ public function watermark($imagePath, $positionX = 0, $positionY = 0, $opacity =
         } elseif ($this->getWatermarkPosition() == self::POSITION_CENTER) {
             $positionX = $this->_imageSrcWidth / 2 - imagesx($watermark) / 2;
             $positionY = $this->_imageSrcHeight / 2 - imagesy($watermark) / 2;
-            imagecopymerge(
+            $this->copyImageWithAlphaPercentage(
                 $this->_imageHandler,
                 $watermark,
                 $positionX,
@@ -478,7 +481,7 @@ public function watermark($imagePath, $positionX = 0, $positionY = 0, $opacity =
             );
         } elseif ($this->getWatermarkPosition() == self::POSITION_TOP_RIGHT) {
             $positionX = $this->_imageSrcWidth - imagesx($watermark);
-            imagecopymerge(
+            $this->copyImageWithAlphaPercentage(
                 $this->_imageHandler,
                 $watermark,
                 $positionX,
@@ -490,7 +493,7 @@ public function watermark($imagePath, $positionX = 0, $positionY = 0, $opacity =
                 $this->getWatermarkImageOpacity()
             );
         } elseif ($this->getWatermarkPosition() == self::POSITION_TOP_LEFT) {
-            imagecopymerge(
+            $this->copyImageWithAlphaPercentage(
                 $this->_imageHandler,
                 $watermark,
                 $positionX,
@@ -504,7 +507,7 @@ public function watermark($imagePath, $positionX = 0, $positionY = 0, $opacity =
         } elseif ($this->getWatermarkPosition() == self::POSITION_BOTTOM_RIGHT) {
             $positionX = $this->_imageSrcWidth - imagesx($watermark);
             $positionY = $this->_imageSrcHeight - imagesy($watermark);
-            imagecopymerge(
+            $this->copyImageWithAlphaPercentage(
                 $this->_imageHandler,
                 $watermark,
                 $positionX,
@@ -517,7 +520,7 @@ public function watermark($imagePath, $positionX = 0, $positionY = 0, $opacity =
             );
         } elseif ($this->getWatermarkPosition() == self::POSITION_BOTTOM_LEFT) {
             $positionY = $this->_imageSrcHeight - imagesy($watermark);
-            imagecopymerge(
+            $this->copyImageWithAlphaPercentage(
                 $this->_imageHandler,
                 $watermark,
                 $positionX,
@@ -531,7 +534,7 @@ public function watermark($imagePath, $positionX = 0, $positionY = 0, $opacity =
         }
 
         if ($tile === false && $merged === false) {
-            imagecopymerge(
+            $this->copyImageWithAlphaPercentage(
                 $this->_imageHandler,
                 $watermark,
                 $positionX,
@@ -547,7 +550,7 @@ public function watermark($imagePath, $positionX = 0, $positionY = 0, $opacity =
             $offsetY = $positionY;
             while ($offsetY <= $this->_imageSrcHeight + imagesy($watermark)) {
                 while ($offsetX <= $this->_imageSrcWidth + imagesx($watermark)) {
-                    imagecopymerge(
+                    $this->copyImageWithAlphaPercentage(
                         $this->_imageHandler,
                         $watermark,
                         $offsetX,
@@ -778,4 +781,106 @@ protected function _createEmptyImage($width, $height)
         $this->imageDestroy();
         $this->_imageHandler = $image;
     }
+
+    /**
+     * Copy source image onto destination image with given alpha percentage
+     *
+     * @internal The arguments and functionality is the same as imagecopymerge
+     *           but with proper handling of alpha transparency
+     *
+     * @param resource $destinationImage
+     * @param resource $sourceImage
+     * @param int $destinationX
+     * @param int $destinationY
+     * @param int $sourceX
+     * @param int $sourceY
+     * @param int $sourceWidth
+     * @param int $sourceHeight
+     * @param int $alphaPercentage
+     *
+     * @return bool
+     * @SuppressWarnings(PHPMD.CyclomaticComplexity)
+     * @SuppressWarnings(PHPMD.NPathComplexity)
+     * @SuppressWarnings(PHPMD.ExcessiveMethodLength)
+     */
+    private function copyImageWithAlphaPercentage(
+        $destinationImage,
+        $sourceImage,
+        $destinationX,
+        $destinationY,
+        $sourceX,
+        $sourceY,
+        $sourceWidth,
+        $sourceHeight,
+        $alphaPercentage
+    ) {
+        if (imageistruecolor($destinationImage) === false || imageistruecolor($sourceImage) === false) {
+            return imagecopymerge(
+                $destinationImage,
+                $sourceImage,
+                $destinationX,
+                $destinationY,
+                $sourceX,
+                $sourceY,
+                $sourceWidth,
+                $sourceHeight,
+                $alphaPercentage
+            );
+        }
+
+        if ($alphaPercentage >= 100) {
+            return imagecopy(
+                $destinationImage,
+                $sourceImage,
+                $destinationX,
+                $destinationY,
+                $sourceX,
+                $sourceY,
+                $sourceWidth,
+                $sourceHeight
+            );
+        }
+
+        if ($alphaPercentage < 0) {
+            return false;
+        }
+
+        $sizeX = imagesx($sourceImage);
+        $sizeY = imagesy($sourceImage);
+        if ($sizeX === false || $sizeY === false || $sizeX === 0 || $sizeY === 0) {
+            return false;
+        }
+
+        $tmpImg = imagecreatetruecolor($sourceWidth, $sourceHeight);
+        if ($tmpImg === false) {
+            return false;
+        }
+
+        if (imagealphablending($tmpImg, false) === false) {
+            return false;
+        }
+
+        if (imagecopy($tmpImg, $sourceImage, 0, 0, 0, 0, $sizeX, $sizeY) === false) {
+            return false;
+        }
+
+        $transparency = 127 - (($alphaPercentage*127)/100);
+        if (imagefilter($tmpImg, IMG_FILTER_COLORIZE, 0, 0, 0, $transparency) === false) {
+            return false;
+        }
+
+        $result = imagecopy(
+            $destinationImage,
+            $tmpImg,
+            $destinationX,
+            $destinationY,
+            $sourceX,
+            $sourceY,
+            $sourceWidth,
+            $sourceHeight
+        );
+        imagedestroy($tmpImg);
+
+        return $result;
+    }
 }

dev/tests/integration/testsuite/Magento/Framework/Image/_files/watermark_alpha_base_image.jpg

@@ -269,15 +269,17 @@ public function watermark($imagePath, $positionX = 0, $positionY = 0, $opacity =
             );
         }
 
-        if (method_exists($watermark, 'setImageOpacity')) {
-            // available from imagick 6.3.1
-            $watermark->setImageOpacity($opacity);
-        } else {
-            // go to each pixel and make it transparent
-            $watermark->paintTransparentImage($watermark->getImagePixelColor(0, 0), 1, 65530);
-            $watermark->evaluateImage(\Imagick::EVALUATE_SUBTRACT, 1 - $opacity, \Imagick::CHANNEL_ALPHA);
+        if (method_exists($watermark, 'getImageAlphaChannel')) {
+            // available from imagick 6.4.0
+            if ($watermark->getImageAlphaChannel() == 0) {
+                $watermark->setImageAlphaChannel(\Imagick::ALPHACHANNEL_OPAQUE);
+            }
         }
 
+        $compositeChannels = \Imagick::CHANNEL_ALL;
+        $watermark->evaluateImage(\Imagick::EVALUATE_MULTIPLY, $opacity, \Imagick::CHANNEL_OPACITY);
+        $compositeChannels &= ~(\Imagick::CHANNEL_OPACITY);
+
         switch ($this->getWatermarkPosition()) {
             case self::POSITION_STRETCH:
                 $watermark->sampleImage($this->_imageSrcWidth, $this->_imageSrcHeight);
@@ -309,14 +311,26 @@ public function watermark($imagePath, $positionX = 0, $positionY = 0, $opacity =
                 $offsetY = $positionY;
                 while ($offsetY <= $this->_imageSrcHeight + $watermark->getImageHeight()) {
                     while ($offsetX <= $this->_imageSrcWidth + $watermark->getImageWidth()) {
-                        $this->_imageHandler->compositeImage($watermark, \Imagick::COMPOSITE_OVER, $offsetX, $offsetY);
+                        $this->_imageHandler->compositeImage(
+                            $watermark,
+                            \Imagick::COMPOSITE_OVER,
+                            $offsetX,
+                            $offsetY,
+                            $compositeChannels
+                        );
                         $offsetX += $watermark->getImageWidth();
                     }
                     $offsetX = $positionX;
                     $offsetY += $watermark->getImageHeight();
                 }
             } else {
-                $this->_imageHandler->compositeImage($watermark, \Imagick::COMPOSITE_OVER, $positionX, $positionY);
+                $this->_imageHandler->compositeImage(
+                    $watermark,
+                    \Imagick::COMPOSITE_OVER,
+                    $positionX,
+                    $positionY,
+                    $compositeChannels
+                );
             }
         } catch (\ImagickException $e) {
             throw new \Exception('Unable to create watermark.', $e->getCode(), $e);