Add support for Grayscale+Alpha PNGs

src/Modifiers/ContainModifier.php

@@ -57,6 +57,11 @@ private function contain(FrameInterface $frame, SizeInterface $resize, ColorInte
             'no_rotate' => true,
         ]);
 
+        if ($resized->bands < 3) {
+            // Grayscale -> RGB
+            $resized = $resized->colourspace('srgb');
+        }
+
         if (!$resized->hasAlpha()) {
             $resized = $resized->bandjoin_const(255);
         }

src/Modifiers/CropModifier.php

@@ -76,22 +76,22 @@ private function background(SizeInterface $resizeTo, ImageInterface $image): Vip
             $bgColor->channel(Blue::class)->value(),
         ];
 
-        $originalImage = $image->core()->native();
-        if ($originalImage->bands === 1) {
+        $imageNative = $image->core()->native();
+        if ($imageNative->bands < 3) {
             // Grayscale -> RGB
-            $originalImage = $originalImage->colourspace('srgb');
+            $imageNative = $imageNative->colourspace('srgb');
         }
 
         // original image and background must have the same number of bands
-        if ($originalImage->hasAlpha()) {
+        if ($imageNative->hasAlpha()) {
             $bands[] = $bgColor->channel(Alpha::class)->value();
         }
 
         return VipsImage::black(1, 1)
             ->add($bgColor->channel(Red::class)->value())
-            ->cast($originalImage->format)
+            ->cast($imageNative->format)
             ->embed(0, 0, $resizeTo->width(), $resizeTo->height(), ['extend' => Extend::COPY])
-            ->copy(['interpretation' => $originalImage->interpretation])
+            ->copy(['interpretation' => $imageNative->interpretation])
             ->bandjoin($bands);
     }
 
@@ -136,6 +136,11 @@ private function cropFrame(
         );
 
         if ($crop->width() > $originalSize->width() || $cropped->height < $crop->height()) {
+            if ($cropped->bands < 3) {
+                // Grayscale -> RGB
+                $cropped = $cropped->colourspace('srgb');
+            }
+
             $cropped = $background->insert(
                 $cropped,
                 max($offset_x * -1, 0),

src/Modifiers/PadModifier.php

@@ -55,11 +55,12 @@ private function pad(FrameInterface $frame, SizeInterface $resize, ColorInterfac
             'no_rotate' => true,
         ]);
 
+        if ($resized->bands < 3) {
+            // Grayscale -> RGB
+            $resized = $resized->colourspace('srgb');
+        }
+
         if (!$resized->hasAlpha()) {
-            if ($resized->bands === 1) {
-                // Grayscale -> RGB
-                $resized = $resized->colourspace('srgb');
-            }
             $resized = $resized->bandjoin_const(255);
         }
 

tests/Unit/Modifiers/ContainModifierTest.php

@@ -65,4 +65,28 @@ public function testModifyContainAnimated(): void
             $this->assertColor(255, 255, 255, 0, $frame->toImage(new Driver())->pickColor(0, 0));
         }
     }
+
+    public function testModifyContainGrayscale(): void
+    {
+        $image = $this->readTestImage('grayscale.png');
+        $this->assertEquals(150, $image->width());
+        $this->assertEquals(200, $image->height());
+        $image->modify(new ContainModifier(200, 200, 'transparent', 'top'));
+        $this->assertEquals(200, $image->width());
+        $this->assertEquals(200, $image->height());
+        $this->assertColor(255, 255, 255, 0, $image->pickColor(0, 0));
+        $this->assertColor(0, 0, 0, 255, $image->pickColor(50, 0));
+    }
+
+    public function testModifyContainGrayscaleAlpha(): void
+    {
+        $image = $this->readTestImage('grayscale-alpha.png');
+        $this->assertEquals(256, $image->width());
+        $this->assertEquals(256, $image->height());
+        $image->modify(new ContainModifier(258, 256, 'transparent', 'top'));
+        $this->assertEquals(258, $image->width());
+        $this->assertEquals(256, $image->height());
+        $this->assertColor(255, 255, 255, 0, $image->pickColor(0, 0));
+        $this->assertColor(0, 0, 0, 128, $image->pickColor(1, 0));
+    }
 }

tests/Unit/Modifiers/CropModifierTest.php

@@ -100,4 +100,16 @@ public function testCropGrayscale(): void
         // Ensure the image is encodable
         $image->encode();
     }
+
+    public function testCropGrayscaleAlpha(): void
+    {
+        $image = $this->readTestImage('grayscale-alpha.png');
+        $image->modify(new CropModifier(258, 258, 0, 0, 'ff0000', 'center'));
+        $this->assertColor(255, 0, 0, 255, $image->pickColor(0, 0));
+        $this->assertColor(0, 0, 0, 128, $image->pickColor(1, 1));
+        $this->assertColor(255, 255, 255, 128, $image->pickColor(256, 1));
+
+        // Ensure the image is encodable
+        $image->encode();
+    }
 }

tests/Unit/Modifiers/PadModifierTest.php

@@ -50,4 +50,18 @@ public function testModifyGrayscale(): void
         $this->assertColor(255, 0, 0, 255, $image->pickColor(199, 0));
         $this->assertColor(255, 0, 0, 255, $image->pickColor(199, 199));
     }
+
+    public function testModifyGrayscaleAlpha(): void
+    {
+        $image = $this->readTestImage('grayscale-alpha.png');
+        $this->assertEquals(256, $image->width());
+        $this->assertEquals(256, $image->height());
+        $image->modify(new PadModifier(258, 258, 'f00'));
+        $this->assertEquals(258, $image->width());
+        $this->assertEquals(258, $image->height());
+        $this->assertColor(255, 0, 0, 255, $image->pickColor(0, 0));
+        $this->assertColor(255, 0, 0, 255, $image->pickColor(0, 257));
+        $this->assertColor(255, 0, 0, 255, $image->pickColor(257, 0));
+        $this->assertColor(255, 0, 0, 255, $image->pickColor(257, 257));
+    }
 }