Add support for LUTs in rasterized images (#274)

Author: PrinsFrank

src/Document/Image/ColorSpace/ColorSpace.php

@@ -17,7 +17,7 @@ class ColorSpace {
     public function __construct(
         public readonly bool $isIndexed,
         public readonly DeviceColorSpaceNameValue|CIEColorSpaceNameValue|SpecialColorSpaceNameValue $nameValue,
-        public readonly DecoratedObject|null $objOrInlineValueLUT,
+        public readonly DecoratedObject|null $LUTObj,
         public readonly string|null $fallbackLUT,
         public readonly ?int $maxIndexLUT,
     ) {
@@ -32,9 +32,9 @@ public function getComponents(): Components {
             return $this->components = $this->nameValue->getComponents();
         }
 
-        if ($this->objOrInlineValueLUT?->getDictionary()->getTypeForKey(DictionaryKey::N) !== null) {
+        if ($this->LUTObj?->getDictionary()->getTypeForKey(DictionaryKey::N) !== null) {
             return $this->components = Components::tryFrom(
-                $this->objOrInlineValueLUT
+                $this->LUTObj
                     ->getDictionary()
                     ->getValueForKey(DictionaryKey::N, IntegerValue::class)
                     ->value ?? throw new RuntimeException('Unable to determine number of components for color space')

src/Document/Image/RasterizedImage.php

@@ -29,23 +29,42 @@ public static function toPNG(ColorSpace $colorSpace, int $width, int $height, in
         $pixelIndex = 0;
         for ($y = 0; $y < $height; $y++) {
             for ($x = 0; $x < $width; $x++) {
-                $color = match ($colorSpace->getComponents()) {
-                    Components::RGB => imagecolorallocate($image, ord($content->read($pixelIndex, 1)), ord($content->read($pixelIndex + 1, 1)), ord($content->read($pixelIndex + 2, 1))),
-                    Components::Gray => imagecolorallocate($image, $value = ord($content->read($pixelIndex, 1)), $value, $value),
-                    Components::CMYK => imagecolorallocate(
-                        $image,
-                        min(255, max(0, (int)(255 * (1 - (ord($content->read($pixelIndex, 1)) / 255)) * (1 - (ord($content->read($pixelIndex + 3, 1)) / 255))))),
-                        min(255, max(0, (int)(255 * (1 - (ord($content->read($pixelIndex + 1, 1)) / 255)) * (1 - (ord($content->read($pixelIndex + 3, 1)) / 255))))),
-                        min(255, max(0, (int)(255 * (1 - (ord($content->read($pixelIndex + 2, 1)) / 255)) * (1 - (ord($content->read($pixelIndex + 3, 1)) / 255))))),
-                    ),
-                };
+                if ($colorSpace->isIndexed && $colorSpace->LUTObj !== null) {
+                    $indexInLUT = ord($content->read($pixelIndex, 1));
+                    if ($indexInLUT > $colorSpace->maxIndexLUT) {
+                        throw new ParseFailureException('Index in LUT is too large');
+                    }
+
+                    $color = match ($colorSpace->getComponents()) {
+                        Components::RGB => imagecolorallocate($image, ord($colorSpace->LUTObj->getStream()->read($indexInLUT, 1)), ord($colorSpace->LUTObj->getStream()->read($indexInLUT + 1, 1)), ord($colorSpace->LUTObj->getStream()->read($indexInLUT + 2, 1))),
+                        Components::Gray => imagecolorallocate($image, $value = ord($colorSpace->LUTObj->getStream()->read($indexInLUT, 1)), $value, $value),
+                        Components::CMYK => imagecolorallocate(
+                            $image,
+                            min(255, max(0, (int)(255 * (1 - (ord($colorSpace->LUTObj->getStream()->read($indexInLUT, 1)) / 255)) * (1 - (ord($colorSpace->LUTObj->getStream()->read($indexInLUT + 3, 1)) / 255))))),
+                            min(255, max(0, (int)(255 * (1 - (ord($colorSpace->LUTObj->getStream()->read($indexInLUT + 1, 1)) / 255)) * (1 - (ord($colorSpace->LUTObj->getStream()->read($indexInLUT + 3, 1)) / 255))))),
+                            min(255, max(0, (int)(255 * (1 - (ord($colorSpace->LUTObj->getStream()->read($indexInLUT + 2, 1)) / 255)) * (1 - (ord($colorSpace->LUTObj->getStream()->read($indexInLUT + 3, 1)) / 255))))),
+                        ),
+                    };
+                    $pixelIndex++;
+                } else {
+                    $color = match ($colorSpace->getComponents()) {
+                        Components::RGB => imagecolorallocate($image, ord($content->read($pixelIndex, 1)), ord($content->read($pixelIndex + 1, 1)), ord($content->read($pixelIndex + 2, 1))),
+                        Components::Gray => imagecolorallocate($image, $value = ord($content->read($pixelIndex, 1)), $value, $value),
+                        Components::CMYK => imagecolorallocate(
+                            $image,
+                            min(255, max(0, (int)(255 * (1 - (ord($content->read($pixelIndex, 1)) / 255)) * (1 - (ord($content->read($pixelIndex + 3, 1)) / 255))))),
+                            min(255, max(0, (int)(255 * (1 - (ord($content->read($pixelIndex + 1, 1)) / 255)) * (1 - (ord($content->read($pixelIndex + 3, 1)) / 255))))),
+                            min(255, max(0, (int)(255 * (1 - (ord($content->read($pixelIndex + 2, 1)) / 255)) * (1 - (ord($content->read($pixelIndex + 3, 1)) / 255))))),
+                        ),
+                    };
+                    $pixelIndex += $colorSpace->getComponents()->value;
+                }
 
                 if ($color === false) {
                     throw new ParseFailureException('Unable to allocate color');
                 }
 
                 imagesetpixel($image, $x, $y, $color);
-                $pixelIndex += $colorSpace->getComponents()->value;
             }
         }