[Feature]: Add PDIndexed support to PDColorSpace

library/src/main/java/com/tom_roush/pdfbox/pdmodel/graphics/color/PDColorSpace.java

@@ -36,6 +36,7 @@
  *
  * @author John Hewson
  * @author Ben Litchfield
+ * @modifiedBy Kanstantsin Valeitsenak
  */
 public abstract class PDColorSpace implements COSObjectable
 {
@@ -186,9 +187,7 @@ else if (name == COSName.DEVICEN)
             }
             else if (name == COSName.INDEXED)
             {
-//                return new PDIndexed(array);
-                Log.e("PdfBox-Android", "Unsupported color space kind: " + name + ". Will try DeviceRGB instead");
-                return PDDeviceRGB.INSTANCE;
+                return new PDIndexed(array);
             }
             else if (name == COSName.SEPARATION)
             {

library/src/main/java/com/tom_roush/pdfbox/pdmodel/graphics/color/PDIndexed.java

@@ -0,0 +1,191 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.tom_roush.pdfbox.pdmodel.graphics.color;
+
+import android.graphics.Bitmap;
+import android.os.Build;
+
+import com.tom_roush.pdfbox.cos.COSArray;
+import com.tom_roush.pdfbox.cos.COSBase;
+import com.tom_roush.pdfbox.cos.COSStream;
+import com.tom_roush.pdfbox.cos.COSString;
+import com.tom_roush.pdfbox.cos.COSNumber;
+import com.tom_roush.pdfbox.cos.COSName;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * Indexed color spaces allow a PDF to use a small color lookup table (palette),
+ * mapping index values to colors in a base color space (such as DeviceRGB).
+ * This is useful for reducing file size when only a limited number of colors are used.
+ *
+ * The Indexed color space is defined by a base color space, a high value (maximum index),
+ * and a lookup table containing the actual color values.
+ *
+ * Example in PDF: [/Indexed /DeviceRGB 255 <...palette bytes...>]
+ *
+ * @author Kanstantsin Valeitsenak
+ */
+
+public class PDIndexed extends PDColorSpace
+{
+    private final PDColorSpace baseColorSpace;
+    private final int highVal;
+    private final byte[] lookupData;
+
+    public PDIndexed(COSArray indexedArray) throws IOException
+    {
+        this.array = indexedArray;
+
+        COSBase base = array.getObject(1);
+        this.baseColorSpace = PDColorSpace.create(base);
+
+        COSNumber hivalObj = (COSNumber) array.getObject(2);
+        this.highVal = hivalObj.intValue();
+
+        COSBase lookup = array.getObject(3);
+
+        if (lookup instanceof COSString)
+        {
+            this.lookupData = ((COSString) lookup).getBytes();
+        }
+        else if (lookup instanceof COSStream)
+        {
+            try (InputStream is = ((COSStream) lookup).createInputStream())
+            {
+                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+                    this.lookupData = is.readAllBytes(); // API 26+
+                } else {
+                    ByteArrayOutputStream baos = new ByteArrayOutputStream();
+                    byte[] buffer = new byte[1024];
+                    int read;
+                    while ((read = is.read(buffer)) != -1) {
+                        baos.write(buffer, 0, read);
+                    }
+                    this.lookupData = baos.toByteArray();
+                }
+            }
+        }
+        else
+        {
+            throw new IOException("Invalid lookup data in Indexed color space");
+        }
+    }
+
+    @Override
+    public String getName()
+    {
+        return COSName.INDEXED.getName();
+    }
+
+    @Override
+    public int getNumberOfComponents()
+    {
+        return 1;
+    }
+
+    @Override
+    public float[] getDefaultDecode(int bitsPerComponent)
+    {
+        return new float[] { 0, highVal };
+    }
+
+    @Override
+    public PDColor getInitialColor()
+    {
+        return new PDColor(new float[] { 0 }, this);
+    }
+
+    @Override
+    public float[] toRGB(float[] value)
+    {
+        int index = Math.round(value[0]);
+        int numColorComponents = baseColorSpace.getNumberOfComponents();
+        int paletteIndex = index * numColorComponents;
+
+        if (paletteIndex + numColorComponents > lookupData.length)
+        {
+            return baseColorSpace.getInitialColor().getComponents(); // fallback
+        }
+
+        float[] rgb = new float[3];
+        float[] component = new float[numColorComponents];
+        for (int i = 0; i < numColorComponents; i++)
+        {
+            int byteVal = lookupData[paletteIndex + i] & 0xFF;
+            component[i] = byteVal / 255f;
+        }
+
+        try {
+            rgb = baseColorSpace.toRGB(component);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+        return rgb;
+    }
+
+    @Override
+    public Bitmap toRGBImage(Bitmap raster) throws IOException {
+        if (raster.getConfig() != Bitmap.Config.ALPHA_8)
+        {
+            throw new IOException("Expected ALPHA_8 bitmap as Indexed source.");
+        }
+
+        int width = raster.getWidth();
+        int height = raster.getHeight();
+
+        Bitmap rgbBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+
+        int[] pixels = new int[width];
+        for (int y = 0; y < height; y++)
+        {
+            raster.getPixels(pixels, 0, width, 0, y, width, 1);
+
+            for (int x = 0; x < width; x++)
+            {
+                int index = pixels[x] & 0xFF;
+
+                int baseIndex = index * baseColorSpace.getNumberOfComponents();
+
+                if (baseIndex + 2 >= lookupData.length)
+                {
+                    rgbBitmap.setPixel(x, y, android.graphics.Color.BLACK); // fallback
+                    continue;
+                }
+
+                float[] baseColor = new float[baseColorSpace.getNumberOfComponents()];
+                for (int i = 0; i < baseColor.length; i++)
+                {
+                    baseColor[i] = (lookupData[baseIndex + i] & 0xFF) / 255f;
+                }
+
+                float[] rgb = baseColorSpace.toRGB(baseColor);
+
+                int r = (int)(rgb[0] * 255);
+                int g = (int)(rgb[1] * 255);
+                int b = (int)(rgb[2] * 255);
+
+                rgbBitmap.setPixel(x, y, android.graphics.Color.rgb(r, g, b));
+            }
+        }
+
+        return rgbBitmap;
+    }
+}