/*
    * 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 org.apache.commons.imaging.formats.ico;
  
  import static org.apache.commons.imaging.common.BinaryFunctions.read2Bytes;
  import static org.apache.commons.imaging.common.BinaryFunctions.read4Bytes;
  import static org.apache.commons.imaging.common.BinaryFunctions.readByte;
  import static org.apache.commons.imaging.common.BinaryFunctions.readBytes;
  
  import java.awt.Dimension;
  import java.awt.image.BufferedImage;
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.io.PrintWriter;
  import java.nio.ByteOrder;
  import java.util.List;
  
  import org.apache.commons.imaging.AbstractImageParser;
  import org.apache.commons.imaging.ImageFormat;
  import org.apache.commons.imaging.ImageFormats;
  import org.apache.commons.imaging.ImageInfo;
  import org.apache.commons.imaging.Imaging;
  import org.apache.commons.imaging.ImagingException;
  import org.apache.commons.imaging.PixelDensity;
  import org.apache.commons.imaging.bytesource.ByteSource;
  import org.apache.commons.imaging.common.Allocator;
  import org.apache.commons.imaging.common.BinaryOutputStream;
  import org.apache.commons.imaging.common.ImageMetadata;
  import org.apache.commons.imaging.formats.bmp.BmpImageParser;
  import org.apache.commons.imaging.palette.PaletteFactory;
  import org.apache.commons.imaging.palette.SimplePalette;
  
  public class IcoImageParser extends AbstractImageParser<IcoImagingParameters> {
      private static final class BitmapHeader {
          public final int size;
          public final int width;
          public final int height;
          public final int planes;
          public final int bitCount;
          public final int compression;
          public final int sizeImage;
          public final int xPelsPerMeter;
          public final int yPelsPerMeter;
          public final int colorsUsed;
          public final int colorsImportant;
  
          BitmapHeader(final int size, final int width, final int height, final int planes, final int bitCount, final int compression, final int sizeImage,
                  final int pelsPerMeter, final int pelsPerMeter2, final int colorsUsed, final int colorsImportant) {
              this.size = size;
              this.width = width;
              this.height = height;
              this.planes = planes;
              this.bitCount = bitCount;
              this.compression = compression;
              this.sizeImage = sizeImage;
              xPelsPerMeter = pelsPerMeter;
              yPelsPerMeter = pelsPerMeter2;
              this.colorsUsed = colorsUsed;
              this.colorsImportant = colorsImportant;
          }
  
          public void dump(final PrintWriter pw) {
              pw.println("BitmapHeader");
  
              pw.println("Size: " + size);
              pw.println("Width: " + width);
              pw.println("Height: " + height);
              pw.println("Planes: " + planes);
              pw.println("BitCount: " + bitCount);
              pw.println("Compression: " + compression);
              pw.println("SizeImage: " + sizeImage);
              pw.println("XPelsPerMeter: " + xPelsPerMeter);
              pw.println("YPelsPerMeter: " + yPelsPerMeter);
              pw.println("ColorsUsed: " + colorsUsed);
              pw.println("ColorsImportant: " + colorsImportant);
          }
      }
  
      private static final class BitmapIconData extends IconData {
          public final BitmapHeader header;
          public final BufferedImage bufferedImage;
  
         BitmapIconData(final IconInfo iconInfo, final BitmapHeader header, final BufferedImage bufferedImage) {
             super(iconInfo);
             this.header = header;
             this.bufferedImage = bufferedImage;
         }
 
         @Override
         protected void dumpSubclass(final PrintWriter pw) {
             pw.println("BitmapIconData");
             header.dump(pw);
             pw.println();
         }
 
         @Override
         public BufferedImage readBufferedImage() throws ImagingException {
             return bufferedImage;
         }
     }
 
     private static final class FileHeader {
         public final int reserved; // Reserved (2 bytes), always 0
         public final int iconType; // IconType (2 bytes), if the image is an
                                    // icon it?s 1, for cursors the value is 2.
         public final int iconCount; // IconCount (2 bytes), number of icons in
                                     // this file.
 
         FileHeader(final int reserved, final int iconType, final int iconCount) {
             this.reserved = reserved;
             this.iconType = iconType;
             this.iconCount = iconCount;
         }
 
         public void dump(final PrintWriter pw) {
             pw.println("FileHeader");
             pw.println("Reserved: " + reserved);
             pw.println("IconType: " + iconType);
             pw.println("IconCount: " + iconCount);
             pw.println();
         }
     }
 
     abstract static class IconData {
         static final int SHALLOW_SIZE = 16;
 
         public final IconInfo iconInfo;
 
         IconData(final IconInfo iconInfo) {
             this.iconInfo = iconInfo;
         }
 
         public void dump(final PrintWriter pw) {
             iconInfo.dump(pw);
             pw.println();
             dumpSubclass(pw);
         }
 
         protected abstract void dumpSubclass(PrintWriter pw);
 
         public abstract BufferedImage readBufferedImage() throws ImagingException;
     }
 
     static class IconInfo {
         static final int SHALLOW_SIZE = 32;
         public final byte width;
         public final byte height;
         public final byte colorCount;
         public final byte reserved;
         public final int planes;
         public final int bitCount;
         public final int imageSize;
         public final int imageOffset;
 
         IconInfo(final byte width, final byte height, final byte colorCount, final byte reserved, final int planes, final int bitCount, final int imageSize,
                 final int imageOffset) {
             this.width = width;
             this.height = height;
             this.colorCount = colorCount;
             this.reserved = reserved;
             this.planes = planes;
             this.bitCount = bitCount;
             this.imageSize = imageSize;
             this.imageOffset = imageOffset;
         }
 
         public void dump(final PrintWriter pw) {
             pw.println("IconInfo");
             pw.println("Width: " + width);
             pw.println("Height: " + height);
             pw.println("ColorCount: " + colorCount);
             pw.println("Reserved: " + reserved);
             pw.println("Planes: " + planes);
             pw.println("BitCount: " + bitCount);
             pw.println("ImageSize: " + imageSize);
             pw.println("ImageOffset: " + imageOffset);
         }
     }
 
     private static final class ImageContents {
         public final FileHeader fileHeader;
         public final IconData[] iconDatas;
 
         ImageContents(final FileHeader fileHeader, final IconData[] iconDatas) {
             this.fileHeader = fileHeader;
             this.iconDatas = iconDatas;
         }
     }
 
     private static final class PngIconData extends IconData {
         public final BufferedImage bufferedImage;
 
         PngIconData(final IconInfo iconInfo, final BufferedImage bufferedImage) {
             super(iconInfo);
             this.bufferedImage = bufferedImage;
         }
 
         @Override
         protected void dumpSubclass(final PrintWriter pw) {
             pw.println("PNGIconData");
             pw.println();
         }
 
         @Override
         public BufferedImage readBufferedImage() {
             return bufferedImage;
         }
     }
 
     private static final String DEFAULT_EXTENSION = ImageFormats.ICO.getDefaultExtension();
 
     private static final String[] ACCEPTED_EXTENSIONS = ImageFormats.ICO.getExtensions();
 
     public IcoImageParser() {
         super(ByteOrder.LITTLE_ENDIAN);
     }
 
     @Override
     public boolean dumpImageFile(final PrintWriter pw, final ByteSource byteSource) throws ImagingException, IOException {
         final ImageContents contents = readImage(byteSource);
         contents.fileHeader.dump(pw);
         for (final IconData iconData : contents.iconDatas) {
             iconData.dump(pw);
         }
         return true;
     }
 
     @Override
     protected String[] getAcceptedExtensions() {
         return ACCEPTED_EXTENSIONS;
     }
 
     @Override
     protected ImageFormat[] getAcceptedTypes() {
         return new ImageFormat[] { ImageFormats.ICO, //
         };
     }
 
     @Override
     public List<BufferedImage> getAllBufferedImages(final ByteSource byteSource) throws ImagingException, IOException {
         final ImageContents contents = readImage(byteSource);
 
         final FileHeader fileHeader = contents.fileHeader;
         final List<BufferedImage> result = Allocator.arrayList(fileHeader.iconCount);
         for (int i = 0; i < fileHeader.iconCount; i++) {
             result.add(contents.iconDatas[i].readBufferedImage());
         }
 
         return result;
     }
 
     @Override
     public final BufferedImage getBufferedImage(final ByteSource byteSource, final IcoImagingParameters params) throws ImagingException, IOException {
         final ImageContents contents = readImage(byteSource);
         final FileHeader fileHeader = contents.fileHeader;
         if (fileHeader.iconCount > 0) {
             return contents.iconDatas[0].readBufferedImage();
         }
         throw new ImagingException("No icons in ICO file");
     }
 
     @Override
     public String getDefaultExtension() {
         return DEFAULT_EXTENSION;
     }
 
     @Override
     public IcoImagingParameters getDefaultParameters() {
         return new IcoImagingParameters();
     }
 
     // TODO should throw UOE
     @Override
     public byte[] getIccProfileBytes(final ByteSource byteSource, final IcoImagingParameters params) throws ImagingException, IOException {
         return null;
     }
 
     // TODO should throw UOE
     @Override
     public ImageInfo getImageInfo(final ByteSource byteSource, final IcoImagingParameters params) throws ImagingException, IOException {
         return null;
     }
 
     // TODO should throw UOE
     @Override
     public Dimension getImageSize(final ByteSource byteSource, final IcoImagingParameters params) throws ImagingException, IOException {
         return null;
     }
 
     // TODO should throw UOE
     @Override
     public ImageMetadata getMetadata(final ByteSource byteSource, final IcoImagingParameters params) throws ImagingException, IOException {
         return null;
     }
 
     @Override
     public String getName() {
         return "ico-Custom";
     }
 
     private IconData readBitmapIconData(final byte[] iconData, final IconInfo fIconInfo) throws ImagingException, IOException {
         final ByteArrayInputStream is = new ByteArrayInputStream(iconData);
         final int size = read4Bytes("size", is, "Not a Valid ICO File", getByteOrder()); // Size (4
         // bytes),
         // size of
         // this
         // structure
         // (always
         // 40)
         final int width = read4Bytes("width", is, "Not a Valid ICO File", getByteOrder()); // Width (4
         // bytes),
         // width of
         // the
         // image
         // (same as
         // iconinfo.width)
         final int height = read4Bytes("height", is, "Not a Valid ICO File", getByteOrder()); // Height
         // (4
         // bytes),
         // scanlines
         // in the
         // color
         // map +
         // transparent
         // map
         // (iconinfo.height
         // * 2)
         final int planes = read2Bytes("planes", is, "Not a Valid ICO File", getByteOrder()); // Planes
         // (2
         // bytes),
         // always
         // 1
         final int bitCount = read2Bytes("bitCount", is, "Not a Valid ICO File", getByteOrder()); // BitCount
         // (2
         // bytes),
         // 1,4,8,16,24,32
         // (see
         // iconinfo
         // for
         // details)
         int compression = read4Bytes("compression", is, "Not a Valid ICO File", getByteOrder()); // Compression
         // (4
         // bytes),
         // we
         // don?t
         // use
         // this
         // (0)
         final int sizeImage = read4Bytes("sizeImage", is, "Not a Valid ICO File", getByteOrder()); // SizeImage
         // (4
         // bytes),
         // we
         // don?t
         // use
         // this
         // (0)
         final int xPelsPerMeter = read4Bytes("xPelsPerMeter", is, "Not a Valid ICO File", getByteOrder()); // XPelsPerMeter (4 bytes), we don?t
         // use this (0)
         final int yPelsPerMeter = read4Bytes("yPelsPerMeter", is, "Not a Valid ICO File", getByteOrder()); // YPelsPerMeter (4 bytes), we don?t
         // use this (0)
         final int colorsUsed = read4Bytes("colorsUsed", is, "Not a Valid ICO File", getByteOrder()); // ColorsUsed
         // (4
         // bytes),
         // we
         // don?t
         // use
         // this
         // (0)
         final int colorsImportant = read4Bytes("ColorsImportant", is, "Not a Valid ICO File", getByteOrder()); // ColorsImportant (4 bytes), we don?t
         // use this (0)
         int redMask = 0;
         int greenMask = 0;
         int blueMask = 0;
         int alphaMask = 0;
         if (compression == 3) {
             redMask = read4Bytes("redMask", is, "Not a Valid ICO File", getByteOrder());
             greenMask = read4Bytes("greenMask", is, "Not a Valid ICO File", getByteOrder());
             blueMask = read4Bytes("blueMask", is, "Not a Valid ICO File", getByteOrder());
         }
         final byte[] restOfFile = readBytes("RestOfFile", is, is.available());
 
         if (size != 40) {
             throw new ImagingException("Not a Valid ICO File: Wrong bitmap header size " + size);
         }
         if (planes != 1) {
             throw new ImagingException("Not a Valid ICO File: Planes can't be " + planes);
         }
 
         if (compression == 0 && bitCount == 32) {
             // 32 BPP RGB icons need an alpha channel, but BMP files don't have
             // one unless BI_BITFIELDS is used...
             compression = 3;
             redMask = 0x00ff0000;
             greenMask = 0x0000ff00;
             blueMask = 0x000000ff;
             alphaMask = 0xff000000;
         }
 
         final BitmapHeader header = new BitmapHeader(size, width, height, planes, bitCount, compression, sizeImage, xPelsPerMeter, yPelsPerMeter, colorsUsed,
                 colorsImportant);
 
         final int bitmapPixelsOffset = 14 + 56 + 4 * (colorsUsed == 0 && bitCount <= 8 ? 1 << bitCount : colorsUsed);
         final int bitmapSize = 14 + 56 + restOfFile.length;
 
         final ByteArrayOutputStream baos = new ByteArrayOutputStream(Allocator.checkByteArray(bitmapSize));
         try (BinaryOutputStream bos = BinaryOutputStream.littleEndian(baos)) {
             bos.write('B');
             bos.write('M');
             bos.write4Bytes(bitmapSize);
             bos.write4Bytes(0);
             bos.write4Bytes(bitmapPixelsOffset);
 
             bos.write4Bytes(56);
             bos.write4Bytes(width);
             bos.write4Bytes(height / 2);
             bos.write2Bytes(planes);
             bos.write2Bytes(bitCount);
             bos.write4Bytes(compression);
             bos.write4Bytes(sizeImage);
             bos.write4Bytes(xPelsPerMeter);
             bos.write4Bytes(yPelsPerMeter);
             bos.write4Bytes(colorsUsed);
             bos.write4Bytes(colorsImportant);
             bos.write4Bytes(redMask);
             bos.write4Bytes(greenMask);
             bos.write4Bytes(blueMask);
             bos.write4Bytes(alphaMask);
             bos.write(restOfFile);
             bos.flush();
         }
 
         final ByteArrayInputStream bmpInputStream = new ByteArrayInputStream(baos.toByteArray());
         final BufferedImage bmpImage = new BmpImageParser().getBufferedImage(bmpInputStream, null);
 
         // Transparency map is optional with 32 BPP icons, because they already
         // have
         // an alpha channel, and Windows only uses the transparency map when it
         // has to
         // display the icon on a < 32 BPP screen. But it's still used instead of
         // alpha
         // if the image would be completely transparent with alpha...
         int tScanlineSize = (width + 7) / 8;
         if (tScanlineSize % 4 != 0) {
             tScanlineSize += 4 - tScanlineSize % 4; // pad scanline to 4
                                                     // byte size.
         }
         final int colorMapSizeBytes = tScanlineSize * (height / 2);
         byte[] transparencyMap = null;
         try {
             transparencyMap = readBytes("transparencyMap", bmpInputStream, colorMapSizeBytes, "Not a Valid ICO File");
         } catch (final IOException ioEx) {
             if (bitCount != 32) {
                 throw ioEx;
             }
         }
 
         boolean allAlphasZero = true;
         if (bitCount == 32) {
             for (int y = 0; allAlphasZero && y < bmpImage.getHeight(); y++) {
                 for (int x = 0; x < bmpImage.getWidth(); x++) {
                     if ((bmpImage.getRGB(x, y) & 0xff000000) != 0) {
                         allAlphasZero = false;
                         break;
                     }
                 }
             }
         }
         BufferedImage resultImage;
         if (allAlphasZero) {
             resultImage = new BufferedImage(bmpImage.getWidth(), bmpImage.getHeight(), BufferedImage.TYPE_INT_ARGB);
             for (int y = 0; y < resultImage.getHeight(); y++) {
                 for (int x = 0; x < resultImage.getWidth(); x++) {
                     int alpha = 0xff;
                     if (transparencyMap != null) {
                         final int alphaByte = 0xff & transparencyMap[tScanlineSize * (bmpImage.getHeight() - y - 1) + x / 8];
                         alpha = 0x01 & alphaByte >> 7 - x % 8;
                         alpha = alpha == 0 ? 0xff : 0x00;
                     }
                     resultImage.setRGB(x, y, alpha << 24 | 0xffffff & bmpImage.getRGB(x, y));
                 }
             }
         } else {
             resultImage = bmpImage;
         }
         return new BitmapIconData(fIconInfo, header, resultImage);
     }
 
     private FileHeader readFileHeader(final InputStream is) throws ImagingException, IOException {
         final int reserved = read2Bytes("Reserved", is, "Not a Valid ICO File", getByteOrder());
         final int iconType = read2Bytes("IconType", is, "Not a Valid ICO File", getByteOrder());
         final int iconCount = read2Bytes("IconCount", is, "Not a Valid ICO File", getByteOrder());
 
         if (reserved != 0) {
             throw new ImagingException("Not a Valid ICO File: reserved is " + reserved);
         }
         if (iconType != 1 && iconType != 2) {
             throw new ImagingException("Not a Valid ICO File: icon type is " + iconType);
         }
 
         return new FileHeader(reserved, iconType, iconCount);
 
     }
 
     private IconData readIconData(final byte[] iconData, final IconInfo fIconInfo) throws ImagingException, IOException {
         final ImageFormat imageFormat = Imaging.guessFormat(iconData);
         if (imageFormat.equals(ImageFormats.PNG)) {
             final BufferedImage bufferedImage = Imaging.getBufferedImage(iconData);
             return new PngIconData(fIconInfo, bufferedImage);
         }
         return readBitmapIconData(iconData, fIconInfo);
     }
 
     private IconInfo readIconInfo(final InputStream is) throws IOException {
         // Width (1 byte), Width of Icon (1 to 255)
         final byte width = readByte("Width", is, "Not a Valid ICO File");
         // Height (1 byte), Height of Icon (1 to 255)
         final byte height = readByte("Height", is, "Not a Valid ICO File");
         // ColorCount (1 byte), Number of colors, either
         // 0 for 24 bit or higher,
         // 2 for monochrome or 16 for 16 color images.
         final byte colorCount = readByte("ColorCount", is, "Not a Valid ICO File");
         // Reserved (1 byte), Not used (always 0)
         final byte reserved = readByte("Reserved", is, "Not a Valid ICO File");
         // Planes (2 bytes), always 1
         final int planes = read2Bytes("Planes", is, "Not a Valid ICO File", getByteOrder());
         // BitCount (2 bytes), number of bits per pixel (1 for monochrome,
         // 4 for 16 colors, 8 for 256 colors, 24 for true colors,
         // 32 for true colors + alpha channel)
         final int bitCount = read2Bytes("BitCount", is, "Not a Valid ICO File", getByteOrder());
         // ImageSize (4 bytes), Length of resource in bytes
         final int imageSize = read4Bytes("ImageSize", is, "Not a Valid ICO File", getByteOrder());
         // ImageOffset (4 bytes), start of the image in the file
         final int imageOffset = read4Bytes("ImageOffset", is, "Not a Valid ICO File", getByteOrder());
 
         return new IconInfo(width, height, colorCount, reserved, planes, bitCount, imageSize, imageOffset);
     }
 
     private ImageContents readImage(final ByteSource byteSource) throws ImagingException, IOException {
         try (InputStream is = byteSource.getInputStream()) {
             final FileHeader fileHeader = readFileHeader(is);
 
             final IconInfo[] fIconInfos = Allocator.array(fileHeader.iconCount, IconInfo[]::new, IconInfo.SHALLOW_SIZE);
             for (int i = 0; i < fileHeader.iconCount; i++) {
                 fIconInfos[i] = readIconInfo(is);
             }
 
             final IconData[] fIconDatas = Allocator.array(fileHeader.iconCount, IconData[]::new, IconData.SHALLOW_SIZE);
             for (int i = 0; i < fileHeader.iconCount; i++) {
                 final byte[] iconData = byteSource.getByteArray(fIconInfos[i].imageOffset, fIconInfos[i].imageSize);
                 fIconDatas[i] = readIconData(iconData, fIconInfos[i]);
             }
 
             return new ImageContents(fileHeader, fIconDatas);
         }
     }
 
     // public boolean extractImages(ByteSource byteSource, File dst_dir,
     // String dst_root, ImageParser encoder) throws ImageReadException,
     // IOException, ImageWriteException
     // {
     // ImageContents contents = readImage(byteSource);
     //
     // FileHeader fileHeader = contents.fileHeader;
     // for (int i = 0; i < fileHeader.iconCount; i++)
     // {
     // IconData iconData = contents.iconDatas[i];
     //
     // BufferedImage image = readBufferedImage(iconData);
     //
     // int size = Math.max(iconData.iconInfo.Width,
     // iconData.iconInfo.Height);
     // File file = new File(dst_dir, dst_root + "_" + size + "_"
     // + iconData.iconInfo.BitCount
     // + encoder.getDefaultExtension());
     // encoder.writeImage(image, new FileOutputStream(file), null);
     // }
     //
     // return true;
     // }
 
     @Override
     public void writeImage(final BufferedImage src, final OutputStream os, IcoImagingParameters params) throws ImagingException, IOException {
         if (params == null) {
             params = new IcoImagingParameters();
         }
         final PixelDensity pixelDensity = params.getPixelDensity();
 
         final PaletteFactory paletteFactory = new PaletteFactory();
         final SimplePalette palette = paletteFactory.makeExactRgbPaletteSimple(src, 256);
         final int bitCount;
         // If we can't obtain an exact rgb palette, we set the bit count to either 24 or 32
         // so there is a relation between having a palette and the bit count.
         if (palette == null) {
             final boolean hasTransparency = paletteFactory.hasTransparency(src);
             if (hasTransparency) {
                 bitCount = 32;
             } else {
                 bitCount = 24;
             }
         } else if (palette.length() <= 2) {
             bitCount = 1;
         } else if (palette.length() <= 16) {
             bitCount = 4;
         } else {
             bitCount = 8;
         }
 
         try (BinaryOutputStream bos = BinaryOutputStream.littleEndian(os)) {
 
             int scanlineSize = (bitCount * src.getWidth() + 7) / 8;
             if (scanlineSize % 4 != 0) {
                 scanlineSize += 4 - scanlineSize % 4; // pad scanline to 4 byte
                                                       // size.
             }
             int tScanlineSize = (src.getWidth() + 7) / 8;
             if (tScanlineSize % 4 != 0) {
                 tScanlineSize += 4 - tScanlineSize % 4; // pad scanline to 4
                                                         // byte size.
             }
             final int imageSize = 40 + 4 * (bitCount <= 8 ? 1 << bitCount : 0) + src.getHeight() * scanlineSize + src.getHeight() * tScanlineSize;
 
             // ICONDIR
             bos.write2Bytes(0); // reserved
             bos.write2Bytes(1); // 1=ICO, 2=CUR
             bos.write2Bytes(1); // count
 
             // ICONDIRENTRY
             int iconDirEntryWidth = src.getWidth();
             int iconDirEntryHeight = src.getHeight();
             if (iconDirEntryWidth > 255 || iconDirEntryHeight > 255) {
                 iconDirEntryWidth = 0;
                 iconDirEntryHeight = 0;
             }
             bos.write(iconDirEntryWidth);
             bos.write(iconDirEntryHeight);
             bos.write(bitCount >= 8 ? 0 : 1 << bitCount);
             bos.write(0); // reserved
             bos.write2Bytes(1); // color planes
             bos.write2Bytes(bitCount);
             bos.write4Bytes(imageSize);
             bos.write4Bytes(22); // image offset
 
             // BITMAPINFOHEADER
             bos.write4Bytes(40); // size
             bos.write4Bytes(src.getWidth());
             bos.write4Bytes(2 * src.getHeight());
             bos.write2Bytes(1); // planes
             bos.write2Bytes(bitCount);
             bos.write4Bytes(0); // compression
             bos.write4Bytes(0); // image size
             bos.write4Bytes(pixelDensity == null ? 0 : (int) Math.round(pixelDensity.horizontalDensityMetres())); // x
                                                                                                                   // pixels
                                                                                                                   // per
                                                                                                                   // meter
             bos.write4Bytes(pixelDensity == null ? 0 : (int) Math.round(pixelDensity.horizontalDensityMetres())); // y
                                                                                                                   // pixels
                                                                                                                   // per
                                                                                                                   // meter
             bos.write4Bytes(0); // colors used, 0 = (1 << bitCount) (ignored)
             bos.write4Bytes(0); // colors important
 
             if (palette != null) {
                 for (int i = 0; i < 1 << bitCount; i++) {
                     if (i < palette.length()) {
                         final int argb = palette.getEntry(i);
                         bos.write3Bytes(argb);
                         bos.write(0);
                     } else {
                         bos.write4Bytes(0);
                     }
                 }
             }
 
             int bitCache = 0;
             int bitsInCache = 0;
             final int rowPadding = scanlineSize - (bitCount * src.getWidth() + 7) / 8;
             for (int y = src.getHeight() - 1; y >= 0; y--) {
                 for (int x = 0; x < src.getWidth(); x++) {
                     final int argb = src.getRGB(x, y);
                     // Remember there is a relation between having a rgb palette and the bit count, see above comment
                     if (palette == null) {
                         if (bitCount == 24) {
                             bos.write3Bytes(argb);
                         } else if (bitCount == 32) {
                             bos.write4Bytes(argb);
                         }
                     } else if (bitCount < 8) {
                         final int rgb = 0xffffff & argb;
                         final int index = palette.getPaletteIndex(rgb);
                         bitCache <<= bitCount;
                         bitCache |= index;
                         bitsInCache += bitCount;
                         if (bitsInCache >= 8) {
                             bos.write(0xff & bitCache);
                             bitCache = 0;
                             bitsInCache = 0;
                         }
                     } else if (bitCount == 8) {
                         final int rgb = 0xffffff & argb;
                         final int index = palette.getPaletteIndex(rgb);
                         bos.write(0xff & index);
                     }
                 }
 
                 if (bitsInCache > 0) {
                     bitCache <<= 8 - bitsInCache;
                     bos.write(0xff & bitCache);
                     bitCache = 0;
                     bitsInCache = 0;
                 }
 
                 for (int x = 0; x < rowPadding; x++) {
                     bos.write(0);
                 }
             }
 
             final int tRowPadding = tScanlineSize - (src.getWidth() + 7) / 8;
             for (int y = src.getHeight() - 1; y >= 0; y--) {
                 for (int x = 0; x < src.getWidth(); x++) {
                     final int argb = src.getRGB(x, y);
                     final int alpha = 0xff & argb >> 24;
                     bitCache <<= 1;
                     if (alpha == 0) {
                         bitCache |= 1;
                     }
                     bitsInCache++;
                     if (bitsInCache >= 8) {
                         bos.write(0xff & bitCache);
                         bitCache = 0;
                         bitsInCache = 0;
                     }
                 }
 
                 if (bitsInCache > 0) {
                     bitCache <<= 8 - bitsInCache;
                     bos.write(0xff & bitCache);
                     bitCache = 0;
                     bitsInCache = 0;
                 }
 
                 for (int x = 0; x < tRowPadding; x++) {
                     bos.write(0);
                 }
             }
         }
     }
 }