Add option to encode interlaced PNG format

src/Drivers/Gd/Encoders/PngEncoder.php

@@ -13,8 +13,11 @@ class PngEncoder extends GenericPngEncoder implements SpecializedInterface
 {
     public function encode(ImageInterface $image): EncodedImage
     {
-        $data = $this->buffered(function () use ($image) {
-            imagepng($image->core()->native(), null, -1);
+        $gd = $image->core()->native();
+        $data = $this->buffered(function () use ($gd) {
+            imageinterlace($gd, $this->interlaced);
+            imagepng($gd, null, -1);
+            imageinterlace($gd, false);
         });
 
         return new EncodedImage($data, 'image/png');

src/Drivers/Imagick/Encoders/PngEncoder.php

@@ -23,6 +23,10 @@ public function encode(ImageInterface $image): EncodedImage
         $imagick->setCompression($compression);
         $imagick->setImageCompression($compression);
 
+        if ($this->interlaced) {
+            $imagick->setInterlaceScheme(Imagick::INTERLACE_LINE);
+        }
+
         return new EncodedImage($imagick->getImagesBlob(), 'image/png');
     }
 }

src/Encoders/PngEncoder.php

@@ -8,7 +8,7 @@
 
 class PngEncoder extends SpecializableEncoder
 {
-    public function __construct()
+    public function __construct(public bool $interlaced = false)
     {
     }
 }

tests/Traits/CanDetectInterlacedPng.php

@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Intervention\Image\Tests\Traits;
+
+use Intervention\Image\Traits\CanBuildFilePointer;
+
+trait CanDetectInterlacedPng
+{
+    use CanBuildFilePointer;
+
+    /**
+     * Checks if the given image data is interlaced encoded PNG format
+     *
+     * @param string $imagedata
+     * @return bool
+     */
+    private function isInterlacedPng(string $imagedata): bool
+    {
+        $f = $this->buildFilePointer($imagedata);
+        $contents = fread($f, 32);
+        fclose($f);
+
+        return ord($contents[28]) != 0;
+    }
+}

tests/Unit/Drivers/Gd/Encoders/PngEncoderTest.php

@@ -8,17 +8,29 @@
 use PHPUnit\Framework\Attributes\RequiresPhpExtension;
 use Intervention\Image\Encoders\PngEncoder;
 use Intervention\Image\Tests\GdTestCase;
+use Intervention\Image\Tests\Traits\CanDetectInterlacedPng;
 
 #[RequiresPhpExtension('gd')]
 #[CoversClass(\Intervention\Image\Encoders\PngEncoder::class)]
 #[CoversClass(\Intervention\Image\Drivers\Gd\Encoders\PngEncoder::class)]
 final class PngEncoderTest extends GdTestCase
 {
+    use CanDetectInterlacedPng;
+
     public function testEncode(): void
     {
         $image = $this->createTestImage(3, 2);
         $encoder = new PngEncoder();
         $result = $encoder->encode($image);
         $this->assertMediaType('image/png', (string) $result);
     }
+
+    public function testEncodeInterlaced(): void
+    {
+        $image = $this->createTestImage(3, 2);
+        $encoder = new PngEncoder(interlaced: true);
+        $result = $encoder->encode($image);
+        $this->assertMediaType('image/png', (string) $result);
+        $this->assertTrue($this->isInterlacedPng((string) $result));
+    }
 }

tests/Unit/Drivers/Imagick/Encoders/PngEncoderTest.php

@@ -8,17 +8,29 @@
 use PHPUnit\Framework\Attributes\RequiresPhpExtension;
 use Intervention\Image\Encoders\PngEncoder;
 use Intervention\Image\Tests\ImagickTestCase;
+use Intervention\Image\Tests\Traits\CanDetectInterlacedPng;
 
 #[RequiresPhpExtension('imagick')]
 #[CoversClass(\Intervention\Image\Encoders\PngEncoder::class)]
 #[CoversClass(\Intervention\Image\Drivers\Imagick\Encoders\PngEncoder::class)]
 final class PngEncoderTest extends ImagickTestCase
 {
+    use CanDetectInterlacedPng;
+
     public function testEncode(): void
     {
         $image = $this->createTestImage(3, 2);
-        $encoder = new PngEncoder(75);
+        $encoder = new PngEncoder();
+        $result = $encoder->encode($image);
+        $this->assertMediaType('image/png', (string) $result);
+    }
+
+    public function testEncodeInterlaced(): void
+    {
+        $image = $this->createTestImage(3, 2);
+        $encoder = new PngEncoder(interlaced: true);
         $result = $encoder->encode($image);
         $this->assertMediaType('image/png', (string) $result);
+        $this->assertTrue($this->isInterlacedPng((string) $result));
     }
 }