Add Image::reduceColors()

src/Drivers/Gd/Modifiers/LimitColorsModifier.php

@@ -1,62 +0,0 @@
-<?php
-
-namespace Intervention\Image\Drivers\Gd\Modifiers;
-
-use Intervention\Image\Drivers\DriverSpecializedModifier;
-use Intervention\Image\Interfaces\ImageInterface;
-
-/**
- * @property int $limit
- * @property int $threshold
- */
-class LimitColorsModifier extends DriverSpecializedModifier
-{
-    public function apply(ImageInterface $image): ImageInterface
-    {
-        // no color limit: no reduction
-        if ($this->limit === 0) {
-            return $image;
-        }
-
-        // limit is over threshold: no reduction
-        if ($this->limit > $this->threshold) {
-            return $image;
-        }
-
-        $width = $image->width();
-        $height = $image->height();
-
-        foreach ($image as $frame) {
-            // limitied color image must be palette (indexed) GDImage
-            $reduced = imagecreate($width, $height);
-
-            // save alpha channel
-            imagesavealpha($reduced, true);
-
-            // create matte
-            $matte = imagecolorallocatealpha($reduced, 255, 255, 255, 127);
-
-            // fill with matte
-            imagefill($reduced, 0, 0, $matte);
-
-            // disable alpha blending for the copy process
-            imagealphablending($reduced, false);
-
-            // set transparency and get transparency index
-            imagecolortransparent($reduced, $matte);
-
-            // copy original image (colors are limited automatically in the copy process)
-            imagecopy($reduced, $frame->native(), 0, 0, 0, 0, $width, $height);
-
-            // reduce limit by one to include possible transparency in palette
-            // $limit = imagecolortransparent($frame->native()) === -1 ? $this->limit : $this->limit - 1;
-
-            // decrease colors
-            // imagetruecolortopalette($reduced, true, $limit);
-
-            $frame->setNative($reduced);
-        }
-
-        return $image;
-    }
-}

src/Drivers/Gd/Modifiers/QuantizeColorsModifier.php

@@ -0,0 +1,56 @@
+<?php
+
+namespace Intervention\Image\Drivers\Gd\Modifiers;
+
+use Intervention\Image\Drivers\DriverSpecializedModifier;
+use Intervention\Image\Exceptions\InputException;
+use Intervention\Image\Interfaces\ImageInterface;
+
+/**
+ * @property int $limit
+ * @property mixed $background
+ */
+class QuantizeColorsModifier extends DriverSpecializedModifier
+{
+    public function apply(ImageInterface $image): ImageInterface
+    {
+        if ($this->limit <= 0) {
+            throw new InputException('Quantization limit must be greater than 0.');
+        }
+
+        // no color reduction if the limit is higher than the colors in the img
+        $colorCount = imagecolorstotal($image->core()->native());
+        if ($colorCount > 0 && $this->limit > $colorCount) {
+            return $image;
+        }
+
+        $width = $image->width();
+        $height = $image->height();
+
+        $background = $this->driver()->colorProcessor($image->colorspace())->colorToNative(
+            $this->driver()->handleInput($this->background)
+        );
+
+        foreach ($image as $frame) {
+            // create new image for color quantization
+            $reduced = imagecreatetruecolor($width, $height);
+
+            // fill with background
+            imagefill($reduced, 0, 0, $background);
+
+            // set transparency
+            imagecolortransparent($reduced, $background);
+
+            // copy original image (colors are limited automatically in the copy process)
+            imagecopy($reduced, $frame->native(), 0, 0, 0, 0, $width, $height);
+
+            // gd library does not support color quantization directly therefore the
+            // colors are decrease by transforming the image to a palette version
+            imagetruecolortopalette($reduced, true, $this->limit);
+
+            $frame->setNative($reduced);
+        }
+
+        return $image;
+    }
+}

src/Drivers/Imagick/Modifiers/QuantizeColorsModifier.php

@@ -3,23 +3,23 @@
 namespace Intervention\Image\Drivers\Imagick\Modifiers;
 
 use Intervention\Image\Drivers\DriverSpecializedModifier;
+use Intervention\Image\Exceptions\InputException;
 use Intervention\Image\Interfaces\ImageInterface;
 
 /**
  * @property int $limit
- * @property int $threshold
+ * @property mixed $background
  */
-class LimitColorsModifier extends DriverSpecializedModifier
+class QuantizeColorsModifier extends DriverSpecializedModifier
 {
     public function apply(ImageInterface $image): ImageInterface
     {
-        // no color limit: no reduction
-        if ($this->limit === 0) {
-            return $image;
+        if ($this->limit <= 0) {
+            throw new InputException('Quantization limit must be greater than 0.');
         }
 
-        // limit is over threshold: no reduction
-        if ($this->limit > $this->threshold) {
+        // no color reduction if the limit is higher than the colors in the img
+        if ($this->limit > $image->core()->native()->getImageColors()) {
             return $image;
         }
 

src/Image.php

@@ -64,6 +64,7 @@ use Intervention\Image\Modifiers\PixelateModifier;
 use Intervention\Image\Modifiers\PlaceModifier;
 use Intervention\Image\Modifiers\ProfileModifier;
 use Intervention\Image\Modifiers\ProfileRemovalModifier;
+use Intervention\Image\Modifiers\QuantizeColorsModifier;
 use Intervention\Image\Modifiers\RemoveAnimationModifier;
 use Intervention\Image\Modifiers\ResizeCanvasModifier;
 use Intervention\Image\Modifiers\ResizeCanvasRelativeModifier;
@@ -366,6 +367,16 @@ final class Image implements ImageInterface, Countable
         return $this->modify(new ProfileRemovalModifier());
     }
 
+    /**
+     * {@inheritdoc}
+     *
+     * @see ImageInterface::reduceColors()
+     */
+    public function reduceColors(int $limit, mixed $background = 'transparent'): ImageInterface
+    {
+        return $this->modify(new QuantizeColorsModifier($limit, $background));
+    }
+
     /**
      * {@inheritdoc}
      *

src/Interfaces/ImageInterface.php

@@ -198,6 +198,14 @@ interface ImageInterface extends IteratorAggregate, Countable
      */
     public function removeProfile(): ImageInterface;
 
+    /**
+     * Apply color quantization to the current image
+     *
+     * @param int $limit
+     * @return ImageInterface
+     */
+    public function reduceColors(int $limit): ImageInterface;
+
     /**
      * Sharpen the current image with given strength
      *

src/Modifiers/LimitColorsModifier.php

@@ -1,12 +0,0 @@
-<?php
-
-namespace Intervention\Image\Modifiers;
-
-class LimitColorsModifier extends AbstractModifier
-{
-    public function __construct(
-        public int $limit = 0,
-        public int $threshold = 256
-    ) {
-    }
-}

src/Modifiers/QuantizeColorsModifier.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace Intervention\Image\Modifiers;
+
+class QuantizeColorsModifier extends AbstractModifier
+{
+    public function __construct(
+        public int $limit,
+        public mixed $background = 'ffffff'
+    ) {
+    }
+}