Implement color limit for PNG & GIF encoders

src/Drivers/Abstract/AbstractImage.php

@@ -70,17 +70,17 @@ abstract class AbstractImage implements ImageInterface
         );
     }
 
-    public function toGif(): EncodedImage
+    public function toGif(int $color_limit = 0): EncodedImage
     {
         return $this->encode(
-            $this->resolveDriverClass('Encoders\GifEncoder')
+            $this->resolveDriverClass('Encoders\GifEncoder', $color_limit)
         );
     }
 
-    public function toPng(): EncodedImage
+    public function toPng(int $color_limit = 0): EncodedImage
     {
         return $this->encode(
-            $this->resolveDriverClass('Encoders\PngEncoder')
+            $this->resolveDriverClass('Encoders\PngEncoder', $color_limit)
         );
     }
 

src/Drivers/Gd/Encoders/GifEncoder.php

@@ -4,20 +4,29 @@ namespace Intervention\Image\Drivers\Gd\Encoders;
 
 use Intervention\Gif\Builder as GifBuilder;
 use Intervention\Image\Drivers\Abstract\Encoders\AbstractEncoder;
+use Intervention\Image\Drivers\Gd\Traits\CanReduceColors;
 use Intervention\Image\EncodedImage;
 use Intervention\Image\Interfaces\EncoderInterface;
 use Intervention\Image\Interfaces\ImageInterface;
 
 class GifEncoder extends AbstractEncoder implements EncoderInterface
 {
+    use CanReduceColors;
+
+    public function __construct(protected int $color_limit = 0)
+    {
+        //
+    }
+
     public function encode(ImageInterface $image): EncodedImage
     {
         if ($image->isAnimated()) {
             return $this->encodeAnimated($image);
         }
 
-        $data = $this->getBuffered(function () use ($image) {
-            imagegif($image->frame()->core());
+        $gd = $this->maybeReduceColors($image->frame()->core(), $this->color_limit);
+        $data = $this->getBuffered(function () use ($gd) {
+            imagegif($gd);
         });
 
         return new EncodedImage($data, 'image/gif');
@@ -32,8 +41,10 @@ class GifEncoder extends AbstractEncoder implements EncoderInterface
         );
 
         foreach ($image as $frame) {
-            $source = $this->encode($frame->toImage());
-            $builder->addFrame($source, $frame->delay());
+            $builder->addFrame(
+                $this->encode($frame->toImage()),
+                $frame->delay()
+            );
         }
 
         return new EncodedImage($builder->encode(), 'image/gif');

src/Drivers/Gd/Encoders/PngEncoder.php

@@ -3,16 +3,25 @@
 namespace Intervention\Image\Drivers\Gd\Encoders;
 
 use Intervention\Image\Drivers\Abstract\Encoders\AbstractEncoder;
+use Intervention\Image\Drivers\Gd\Traits\CanReduceColors;
 use Intervention\Image\EncodedImage;
 use Intervention\Image\Interfaces\EncoderInterface;
 use Intervention\Image\Interfaces\ImageInterface;
 
 class PngEncoder extends AbstractEncoder implements EncoderInterface
 {
+    use CanReduceColors;
+
+    public function __construct(protected int $color_limit = 0)
+    {
+        //
+    }
+
     public function encode(ImageInterface $image): EncodedImage
     {
-        $data = $this->getBuffered(function () use ($image) {
-            imagepng($image->frame()->core(), null, -1);
+        $gd = $this->maybeReduceColors($image->frame()->core(), $this->color_limit);
+        $data = $this->getBuffered(function () use ($gd) {
+            imagepng($gd, null, -1);
         });
 
         return new EncodedImage($data, 'image/png');

src/Drivers/Gd/Traits/CanReduceColors.php

@@ -0,0 +1,59 @@
+<?php
+
+namespace Intervention\Image\Drivers\Gd\Traits;
+
+use GdImage;
+
+trait CanReduceColors
+{
+    /**
+     * Reduce colors in a given GdImage to the given limit. Reduction is only
+     * applied when the given limit is under the given threshold
+     *
+     * @param GdImage $gd
+     * @param int $limit
+     * @param int $threshold
+     * @return GdImage
+     */
+    private function maybeReduceColors(GdImage $gd, int $limit, int $threshold = 256): GdImage
+    {
+        // no color limit: no reduction
+        if ($limit === 0) {
+            return $gd;
+        }
+
+        // limit is over threshold: no reduction
+        if ($limit > $threshold) {
+            return $gd;
+        }
+
+        // image size
+        $width = imagesx($gd);
+        $height = imagesy($gd);
+
+        // create empty gd
+        $reduced = imagecreatetruecolor($width, $height);
+
+        // create matte
+        $matte = imagecolorallocatealpha($reduced, 255, 255, 255, 127);
+
+        // fill with matte
+        imagefill($reduced, 0, 0, $matte);
+
+        imagealphablending($reduced, false);
+
+        // set transparency and get transparency index
+        imagecolortransparent($reduced, $matte);
+
+        // copy original image
+        imagecopy($reduced, $gd, 0, 0, 0, 0, $width, $height);
+
+        // reduce limit by one to include possible transparency in palette
+        $limit = imagecolortransparent($gd) === -1 ? $limit : $limit - 1;
+
+        // decrease colors
+        imagetruecolortopalette($reduced, true, $limit);
+
+        return $reduced;
+    }
+}

src/Drivers/Imagick/Encoders/GifEncoder.php

@@ -5,6 +5,7 @@ namespace Intervention\Image\Drivers\Imagick\Encoders;
 use Imagick;
 use Intervention\Image\Drivers\Abstract\Encoders\AbstractEncoder;
 use Intervention\Image\Drivers\Imagick\Image;
+use Intervention\Image\Drivers\Imagick\Traits\CanReduceColors;
 use Intervention\Image\EncodedImage;
 use Intervention\Image\Exceptions\EncoderException;
 use Intervention\Image\Interfaces\EncoderInterface;
@@ -12,6 +13,13 @@ use Intervention\Image\Interfaces\ImageInterface;
 
 class GifEncoder extends AbstractEncoder implements EncoderInterface
 {
+    use CanReduceColors;
+
+    public function __construct(protected int $color_limit = 0)
+    {
+        //
+    }
+
     public function encode(ImageInterface $image): EncodedImage
     {
         $format = 'gif';
@@ -27,6 +35,7 @@ class GifEncoder extends AbstractEncoder implements EncoderInterface
         $imagick->setCompression($compression);
         $imagick->setImageCompression($compression);
         $imagick->optimizeImageLayers();
+        $this->maybeReduceColors($imagick, $this->color_limit);
         $imagick = $imagick->deconstructImages();
 
         return new EncodedImage($imagick->getImagesBlob(), 'image/gif');

src/Drivers/Imagick/Encoders/PngEncoder.php

@@ -4,12 +4,20 @@ namespace Intervention\Image\Drivers\Imagick\Encoders;
 
 use Imagick;
 use Intervention\Image\Drivers\Abstract\Encoders\AbstractEncoder;
+use Intervention\Image\Drivers\Imagick\Traits\CanReduceColors;
 use Intervention\Image\EncodedImage;
 use Intervention\Image\Interfaces\EncoderInterface;
 use Intervention\Image\Interfaces\ImageInterface;
 
 class PngEncoder extends AbstractEncoder implements EncoderInterface
 {
+    use CanReduceColors;
+
+    public function __construct(protected int $color_limit = 0)
+    {
+        //
+    }
+
     public function encode(ImageInterface $image): EncodedImage
     {
         $format = 'png';
@@ -20,6 +28,7 @@ class PngEncoder extends AbstractEncoder implements EncoderInterface
         $imagick->setImageFormat($format);
         $imagick->setCompression($compression);
         $imagick->setImageCompression($compression);
+        $this->maybeReduceColors($imagick, $this->color_limit);
 
         return new EncodedImage($imagick->getImagesBlob(), 'image/png');
     }

src/Drivers/Imagick/Traits/CanReduceColors.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace Intervention\Image\Drivers\Imagick\Traits;
+
+use Imagick;
+
+trait CanReduceColors
+{
+    /**
+     * Returns a Imagick from a given image with reduced colors to a given limit.
+     * Reduction is only applied when the given limit is under the given threshold
+     *
+     * @param Imagick $imagick
+     * @param int $limit
+     * @param int $threshold
+     * @return Imagick
+     */
+    private function maybeReduceColors(Imagick $imagick, int $limit, int $threshold = 256): Imagick
+    {
+        if ($limit === 0) {
+            return $imagick;
+        }
+
+        if ($limit > $threshold) {
+            return $imagick;
+        }
+
+        $imagick->quantizeImage(
+            $limit,
+            $imagick->getImageColorspace(),
+            0,
+            false,
+            false
+        );
+
+        return $imagick;
+    }
+}

src/Interfaces/ImageInterface.php

@@ -121,7 +121,7 @@ interface ImageInterface extends Traversable, Countable
      *
      * @return EncodedImage
      */
-    public function toGif(): EncodedImage;
+    public function toGif(int $color_limit = 0): EncodedImage;
 
     /**
      * Encode image to avif format
@@ -135,7 +135,7 @@ interface ImageInterface extends Traversable, Countable
      *
      * @return EncodedImage
      */
-    public function toPng(): EncodedImage;
+    public function toPng(int $color_limit = 0): EncodedImage;
 
     /**
      * Return color of pixel at given position on given frame position

tests/Drivers/Abstract/AbstractImageTest.php

@@ -11,7 +11,6 @@ use Intervention\Image\Interfaces\EncoderInterface;
 use Intervention\Image\Interfaces\FrameInterface;
 use Intervention\Image\Interfaces\ImageInterface;
 use Intervention\Image\Interfaces\ModifierInterface;
-use Intervention\Image\Resolution;
 use Intervention\Image\Tests\TestCase;
 use Mockery;
 
@@ -120,7 +119,7 @@ class AbstractImageTest extends TestCase
         $encoder->shouldReceive('encode')->with($img)->andReturn($encoded);
 
         $img->shouldReceive('resolveDriverClass')
-                ->with('Encoders\GifEncoder')
+                ->with('Encoders\GifEncoder', 0)
                 ->andReturn($encoder);
 
         $result = $img->toGif();
@@ -136,7 +135,7 @@ class AbstractImageTest extends TestCase
         $encoder->shouldReceive('encode')->with($img)->andReturn($encoded);
 
         $img->shouldReceive('resolveDriverClass')
-                ->with('Encoders\PngEncoder')
+                ->with('Encoders\PngEncoder', 0)
                 ->andReturn($encoder);
 
         $result = $img->toPng();

tests/Drivers/Gd/Encoders/GifEncoderTest.php

@@ -7,6 +7,7 @@ use Intervention\Image\Drivers\Gd\Encoders\GifEncoder;
 use Intervention\Image\Drivers\Gd\Frame;
 use Intervention\Image\Drivers\Gd\Image;
 use Intervention\Image\Tests\TestCase;
+use Intervention\Image\Tests\Traits\CanCreateGdTestImage;
 use Intervention\MimeSniffer\MimeSniffer;
 use Intervention\MimeSniffer\Types\ImageGif;
 
@@ -16,6 +17,8 @@ use Intervention\MimeSniffer\Types\ImageGif;
  */
 class GifEncoderTest extends TestCase
 {
+    use CanCreateGdTestImage;
+
     protected function getTestImage(): Image
     {
         $gd1 = imagecreatetruecolor(30, 20);
@@ -41,4 +44,15 @@ class GifEncoderTest extends TestCase
         $result = $encoder->encode($image);
         $this->assertTrue(MimeSniffer::createFromString($result)->matches(new ImageGif()));
     }
+
+    public function testEncodeReduced(): void
+    {
+        $image = $this->createTestImage('gradient.gif');
+        $gd = $image->frame()->core();
+        $this->assertEquals(15, imagecolorstotal($gd));
+        $encoder = new GifEncoder(2);
+        $result = $encoder->encode($image);
+        $gd = imagecreatefromstring((string) $result);
+        $this->assertEquals(2, imagecolorstotal($gd));
+    }
 }

tests/Drivers/Gd/Encoders/PngEncoderTest.php

@@ -7,6 +7,7 @@ use Intervention\Image\Drivers\Gd\Encoders\PngEncoder;
 use Intervention\Image\Drivers\Gd\Frame;
 use Intervention\Image\Drivers\Gd\Image;
 use Intervention\Image\Tests\TestCase;
+use Intervention\Image\Tests\Traits\CanCreateGdTestImage;
 use Intervention\MimeSniffer\MimeSniffer;
 use Intervention\MimeSniffer\Types\ImagePng;
 
@@ -16,6 +17,8 @@ use Intervention\MimeSniffer\Types\ImagePng;
  */
 class PngEncoderTest extends TestCase
 {
+    use CanCreateGdTestImage;
+
     protected function getTestImage(): Image
     {
         $frame = new Frame(imagecreatetruecolor(3, 2));
@@ -28,6 +31,17 @@ class PngEncoderTest extends TestCase
         $image = $this->getTestImage();
         $encoder = new PngEncoder();
         $result = $encoder->encode($image);
-        $this->assertTrue(MimeSniffer::createFromString($result)->matches(new ImagePng));
+        $this->assertTrue(MimeSniffer::createFromString($result)->matches(ImagePng::class));
+    }
+
+    public function testEncodeReduced(): void
+    {
+        $image = $this->createTestImage('tile.png');
+        $gd = $image->frame()->core();
+        $this->assertEquals(3, imagecolorstotal($gd));
+        $encoder = new PngEncoder(2);
+        $result = $encoder->encode($image);
+        $gd = imagecreatefromstring((string) $result);
+        $this->assertEquals(2, imagecolorstotal($gd));
     }
 }

tests/Drivers/Imagick/Encoders/GifEncoderTest.php

@@ -6,9 +6,9 @@ use Imagick;
 use ImagickPixel;
 use Intervention\Image\Collection;
 use Intervention\Image\Drivers\Imagick\Encoders\GifEncoder;
-use Intervention\Image\Drivers\Imagick\Frame;
 use Intervention\Image\Drivers\Imagick\Image;
 use Intervention\Image\Tests\TestCase;
+use Intervention\Image\Tests\Traits\CanCreateImagickTestImage;
 use Intervention\MimeSniffer\MimeSniffer;
 use Intervention\MimeSniffer\Types\ImageGif;
 
@@ -18,6 +18,8 @@ use Intervention\MimeSniffer\Types\ImageGif;
  */
 class GifEncoderTest extends TestCase
 {
+    use CanCreateImagickTestImage;
+
     protected function getTestImage(): Image
     {
         $imagick = new Imagick();
@@ -47,4 +49,16 @@ class GifEncoderTest extends TestCase
         $result = $encoder->encode($image);
         $this->assertTrue(MimeSniffer::createFromString($result)->matches(new ImageGif()));
     }
+
+    public function testEncodeReduced(): void
+    {
+        $image = $this->createTestImage('gradient.gif');
+        $imagick = $image->frame()->core();
+        $this->assertEquals(15, $imagick->getImageColors());
+        $encoder = new GifEncoder(2);
+        $result = $encoder->encode($image);
+        $imagick = new Imagick();
+        $imagick->readImageBlob((string) $result);
+        $this->assertEquals(2, $imagick->getImageColors());
+    }
 }

tests/Drivers/Imagick/Encoders/PngEncoderTest.php

@@ -8,6 +8,7 @@ use Imagick;
 use ImagickPixel;
 use Intervention\Image\Drivers\Imagick\Encoders\PngEncoder;
 use Intervention\Image\Drivers\Imagick\Image;
+use Intervention\Image\Tests\Traits\CanCreateImagickTestImage;
 use Intervention\MimeSniffer\MimeSniffer;
 use Intervention\MimeSniffer\Types\ImagePng;
 use PHPUnit\Framework\TestCase;
@@ -17,6 +18,8 @@ use PHPUnit\Framework\TestCase;
  */
 final class PngEncoderTest extends TestCase
 {
+    use CanCreateImagickTestImage;
+
     protected function getTestImage(): Image
     {
         $imagick = new Imagick();
@@ -32,4 +35,16 @@ final class PngEncoderTest extends TestCase
         $result = $encoder->encode($image);
         $this->assertTrue(MimeSniffer::createFromString((string) $result)->matches(new ImagePng()));
     }
+
+    public function testEncodeReduced(): void
+    {
+        $image = $this->createTestImage('tile.png');
+        $imagick = $image->frame()->core();
+        $this->assertEquals(3, $imagick->getImageColors());
+        $encoder = new PngEncoder(2);
+        $result = $encoder->encode($image);
+        $imagick = new Imagick();
+        $imagick->readImageBlob((string) $result);
+        $this->assertEquals(2, $imagick->getImageColors());
+    }
 }