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使用 java.awt.image.BufferedImage 创建 BIFF8 BITMAP 记录需要很多时间 - 有没有更好的方法？

2024-04-20

所以我正在创建一个HSSFSheet使用设置背景位图apache poi并拥有自己的低级代码。这https://www.openoffice.org/sc/excelfileformat.pdf https://www.openoffice.org/sc/excelfileformat.pdf声明为Record BITMAP, BIFF8:

像素数据（位图高度线数组，从底线到顶线，见下文）

...

在每行中，所有像素都是从左到右写入的。每个像素都存储为 3 字节数组：像素颜色的红色、绿色和蓝色分量（按此顺序）。通过在最后一个像素后插入零字节，将每行的大小对齐为 4 的倍数。

See picture of the PDF for complete declaration: enter image description here

为了实现这一点，我的方法是使用java.awt.image.BufferedImage有类型BufferedImage.TYPE_3BYTE_BGR。然后以正确的顺序（从底线到顶线）从该 BufferedImage 的光栅中获取所有字节 R G B 并在宽度（x 方向）上填充至 4 的倍数。

参见代码：

import java.io.FileOutputStream;
import java.io.FileInputStream;

import org.apache.poi.hssf.usermodel.*;

import org.apache.poi.hssf.record.RecordBase;
import org.apache.poi.hssf.record.StandardRecord;
import org.apache.poi.hssf.model.InternalSheet;
import org.apache.poi.util.LittleEndianOutput;

import java.lang.reflect.Field;

import java.util.List;
import java.util.ArrayList;
import java.util.Arrays;

import java.awt.image.BufferedImage;
import java.awt.Graphics2D;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;

import javax.imageio.ImageIO;

public class CreateExcelHSSFSheetBackgroundBitmap {

 static List<Byte> getBackgroundBitmapData(String filePath) throws Exception {

  //see https://www.openoffice.org/sc/excelfileformat.pdf - BITMAP

  List<Byte> data = new ArrayList<Byte>();

  // get file byte data in type BufferedImage.TYPE_3BYTE_BGR
  BufferedImage in = ImageIO.read(new FileInputStream(filePath));
  BufferedImage image = new BufferedImage(in.getWidth(), in.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
  Graphics2D graphics = image.createGraphics();
  graphics.drawImage(in, null, 0, 0);
  graphics.dispose();

  short width = (short)image.getWidth();
  short height = (short)image.getHeight();

  // each pixel has 3 bytes but the width bytes must be filled up to multiple of 4
  int widthBytesMultOf4 = (int)((width * 3 + 3) / 4 * 4);

// --- this part takes much time but I have not found any better possibility

  // put the bytes R G B into the data; lines of the bitmap must be from bottom line to top line
  int bytes = 0;
  for (short y = (short)(height - 1); y >= 0; y--) {
   for (short x = 0; x < width; x++) {
    int r = image.getData().getSample(x, y, 2);
    data.add(Byte.valueOf((byte)r));
    bytes++;
    int g = image.getData().getSample(x, y, 1);
    data.add(Byte.valueOf((byte)g));
    bytes++;
    int b = image.getData().getSample(x, y, 0);
    data.add(Byte.valueOf((byte)b));
    bytes++;
   } 
   // fill up x with 0 bytes up to multiple of 4
   for (int x = width * 3; x < widthBytesMultOf4; x++) {
    data.add(Byte.valueOf((byte)0));
    bytes++;
   }
  }

// ---

  // size  12 bytes (additional headers, see below) + picture bytes
  int size = 12 + bytes;

  // get size int as LITTLE_ENDIAN bytes
  ByteBuffer bSize = ByteBuffer.allocate(4);
  bSize.order(ByteOrder.LITTLE_ENDIAN);
  bSize.putInt(size);

  // get width short as LITTLE_ENDIAN bytes
  ByteBuffer bWidth = ByteBuffer.allocate(2);
  bWidth.order(ByteOrder.LITTLE_ENDIAN);
  bWidth.putShort(width);

  // get height short as LITTLE_ENDIAN bytes
  ByteBuffer bHeight = ByteBuffer.allocate(2);
  bHeight.order(ByteOrder.LITTLE_ENDIAN);
  bHeight.putShort(height);

  // put the record headers into the data
  Byte[] dataPart = new Byte[] { 0x09, 0x00, 0x01, 0x00, 
     bSize.array()[0], bSize.array()[1], bSize.array()[2], bSize.array()[3], // size
     //now 12 bytes follow
     0x0C, 0x00, 0x00, 0x00, 
     bWidth.array()[0], bWidth.array()[1], // width
     bHeight.array()[0], bHeight.array()[1], // height
     0x01, 0x00, 0x18, 0x00
   }; 

  data.addAll(0, Arrays.asList(dataPart));

  return data;
 }

 public static void main(String[] args) throws Exception {

  HSSFWorkbook workbook = new HSSFWorkbook();
  HSSFSheet sheet = workbook.createSheet("Sheet1");
  sheet = workbook.createSheet("Sheet2"); // this sheet gets the background image set

  // we need the binary records of the sheet
  // get InternalSheet
  Field _sheet = HSSFSheet.class.getDeclaredField("_sheet");
  _sheet.setAccessible(true); 
  InternalSheet internalsheet = (InternalSheet)_sheet.get(sheet); 

  // get List of RecordBase
  Field _records = InternalSheet.class.getDeclaredField("_records");
  _records.setAccessible(true);
  @SuppressWarnings("unchecked") 
  List<RecordBase> records = (List<RecordBase>)_records.get(internalsheet);

  // get bytes of the image file
  List<Byte> data = getBackgroundBitmapData("dummyText.png"); //PNG must not have transparency

  // do creating BitmapRecord and ContinueRecords from the data in parts of 8220 bytes
  BitmapRecord bitmapRecord = null;
  List<ContinueRecord> continueRecords = new ArrayList<ContinueRecord>();
  int bytes = 0;
  if (data.size() > 8220) {
   bitmapRecord = new BitmapRecord(data.subList(0, 8220));
   bytes = 8220;
   while (bytes < data.size()) {
    if ((bytes + 8220) < data.size()) {
     continueRecords.add(new ContinueRecord(data.subList(bytes, bytes + 8220)));
     bytes += 8220;
    } else {
     continueRecords.add(new ContinueRecord(data.subList(bytes, data.size())));
     break;
    }
   }
  } else {
   bitmapRecord = new BitmapRecord(data);
  }

  // add the records after PageSettingsBlock
  int i = 0;
  for (RecordBase r : records) {
   if (r instanceof org.apache.poi.hssf.record.aggregates.PageSettingsBlock) {
    break;
   }
   i++;
  }
  records.add(++i, bitmapRecord);
  for (ContinueRecord continueRecord : continueRecords) {
   records.add(++i, continueRecord);  
  }

  // debug output
  for (RecordBase r : internalsheet.getRecords()) {
   System.out.println(r);
  }

  // write out workbook
  workbook.write(new FileOutputStream("CreateExcelHSSFSheetBackgroundBitmap.xls"));
  workbook.close();

 }

 static class BitmapRecord extends StandardRecord {

  //see https://www.openoffice.org/sc/excelfileformat.pdf - BITMAP

  List<Byte> data = new ArrayList<Byte>();

  BitmapRecord(List<Byte> data) {
   this.data = data;
  }

  public int getDataSize() { 
   return data.size(); 
  }

  public short getSid() {
   return (short)0x00E9;
  }

  public void serialize(LittleEndianOutput out) {
   for (Byte b : data) {
    out.writeByte(b);
   }
  }
 }

 static class ContinueRecord extends StandardRecord {

  //see https://www.openoffice.org/sc/excelfileformat.pdf - CONTINUE

  List<Byte> data = new ArrayList<Byte>();

  ContinueRecord(List<Byte> data) {
   this.data = data;
  }

  public int getDataSize() { 
   return data.size(); 
  }

  public short getSid() {
   return (short)0x003C;
  }

  public void serialize(LittleEndianOutput out) {
   for (Byte b : data) {
    out.writeByte(b);
   }
  }
 }

}

该代码有效，但之间的部分

// --- this part takes much time but I have not found any better possibility

and

// ---

根据上述奇怪的格式获取它们需要花费很多时间，因为每个像素需要3个字节的R G B。

有谁知道更好的方法？也许上面奇怪的格式并不像我想象的那么奇怪，并且已经有其他用法了？


这是您的代码的修改版本，适用于我，并且速度非常快。

  1. 我在用着byte[] (and ByteArrayOutputStream）到处都是，没有更多List<Byte>.
  2. 由于我们已经有一个BufferedImage of TYPE_3BYTE_BGR，我们几乎可以直接使用它作为 BMP 输出。我们只需要 a) 预先添加一个有效的 BMP 标头，b) 自下而上写入，c) 将每个扫描线（行）填充到 32 位边界，以及 d) 切换 BGR -> RGB 顺序。
  3. 我正在使用Raster将数据行复制（填充）到输出中，因为复制较大的块比复制单个字节更快。

正如评论中已经指出的，该结构是一个标准 BMPBITMAPCOREHEADER（并且没有文件头）。不幸的是，ImageIO BMPImageWriter始终写入文件头并使用BITMAPINFOHEADER这是 40 字节。您可能可以解决这些问题，并使用标准编写器，通过稍微调整数据（提示：文件头包含偏移量 10 处的像素数据的偏移量），但由于核心 BMP 格式实现起来很简单，因此可能就像下面一样容易做到。

虽然文档确实暗示直接使用其他格式（如 PNG 和 JPEG），但我还没有成功地做到这一点。

如果您愿意，可能还有改进的空间，以避免一些字节数组复制（即使用偏移量/长度并将整个数据数组传递给Bitmap/ContinueRecords 而不是Arrays.copyOfRange()).

Code:

import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.awt.image.Raster;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.lang.reflect.Field;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import javax.imageio.ImageIO;

import org.apache.poi.hssf.model.InternalSheet;
import org.apache.poi.hssf.record.RecordBase;
import org.apache.poi.hssf.record.StandardRecord;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.util.LittleEndianOutput;

public class CreateExcelHSSFSheetBackgroundBitmap {

    static byte[] getBackgroundBitmapData(String filePath) throws Exception {

        //see https://www.openoffice.org/sc/excelfileformat.pdf - BITMAP

        // get file byte data in type BufferedImage.TYPE_3BYTE_BGR
        BufferedImage in = ImageIO.read(new FileInputStream(filePath));
        BufferedImage image = new BufferedImage(in.getWidth(), in.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
        Graphics2D graphics = image.createGraphics();
        graphics.drawImage(in, null, 0, 0);
        graphics.dispose();

        // calculate row size (c)
        int rowSize = ((24 * image.getWidth() + 31) / 32) * 4;

        ByteArrayOutputStream output = new ByteArrayOutputStream(image.getHeight() * rowSize * 3 + 1024);

        // put the record headers into the data
        ByteBuffer header = ByteBuffer.allocate(8 + 12);
        header.order(ByteOrder.LITTLE_ENDIAN);

        // Undocumented XLS stuff
        header.putShort((short) 0x09);
        header.putShort((short) 0x01);
        header.putInt(image.getHeight() * rowSize + 12); // Size of image stream

        // BITMAPCOREHEADER (a)
        header.putInt(12);

        header.putShort((short) image.getWidth());
        header.putShort((short) image.getHeight()); // Use -height if writing top-down

        header.putShort((short) 1); // planes, always 1
        header.putShort((short) 24); // bitcount

        output.write(header.array());

        // Output rows bottom-up (b)
        Raster raster = image.getRaster()
                             .createChild(0, 0, image.getWidth(), image.getHeight(), 0, 0, new int[]{2, 1, 0}); // Reverse BGR -> RGB (d)
        byte[] row = new byte[rowSize]; // padded (c)

        for (int i = image.getHeight() - 1; i >= 0; i--) {
            row = (byte[]) raster.getDataElements(0, i, image.getWidth(), 1, row);
            output.write(row);
        }

        return output.toByteArray();
    }

    public static void main(String[] args) throws Exception {
        HSSFWorkbook workbook = new HSSFWorkbook();
        HSSFSheet sheet = workbook.createSheet("Sheet2"); // this sheet gets the background image set

        // we need the binary records of the sheet
        // get InternalSheet
        Field _sheet = HSSFSheet.class.getDeclaredField("_sheet");
        _sheet.setAccessible(true);
        InternalSheet internalsheet = (InternalSheet)_sheet.get(sheet);

        // get List of RecordBase
        Field _records = InternalSheet.class.getDeclaredField("_records");
        _records.setAccessible(true);
        @SuppressWarnings("unchecked")
        List<RecordBase> records = (List<RecordBase>)_records.get(internalsheet);

        // get bytes of the image file
        byte[] data = getBackgroundBitmapData("dummy.png"); //PNG must not have transparency

        // do creating BitmapRecord and ContinueRecords from the data in parts of 8220 bytes
        BitmapRecord bitmapRecord;
        List<ContinueRecord> continueRecords = new ArrayList<>();
        int bytes;

        if (data.length > 8220) {
            bitmapRecord = new BitmapRecord(Arrays.copyOfRange(data, 0, 8220));
            bytes = 8220;
            while (bytes < data.length) {
                if ((bytes + 8220) < data.length) {
                    continueRecords.add(new ContinueRecord(Arrays.copyOfRange(data, bytes, bytes + 8220)));
                    bytes += 8220;
                } else {
                    continueRecords.add(new ContinueRecord(Arrays.copyOfRange(data, bytes, data.length)));
                    break;
                }
            }
        } else {
            bitmapRecord = new BitmapRecord(data);
        }

        // add the records after PageSettingsBlock
        int i = 0;
        for (RecordBase r : records) {
            if (r instanceof org.apache.poi.hssf.record.aggregates.PageSettingsBlock) {
                break;
            }
            i++;
        }
        records.add(++i, bitmapRecord);
        for (ContinueRecord continueRecord : continueRecords) {
            records.add(++i, continueRecord);
        }

        // debug output
        for (RecordBase r : internalsheet.getRecords()) {
            System.out.println(r);
        }

        // write out workbook
        workbook.write(new FileOutputStream("backgroundImage.xls"));
        workbook.close();

    }

    static class BitmapRecord extends StandardRecord {

        //see https://www.openoffice.org/sc/excelfileformat.pdf - BITMAP

        byte[] data;

        BitmapRecord(byte[] data) {
            this.data = data;
        }

        public int getDataSize() {
            return data.length;
        }

        public short getSid() {
            return (short)0x00E9;
        }

        public void serialize(LittleEndianOutput out) {
            out.write(data);
        }
    }

    static class ContinueRecord extends StandardRecord {

        //see https://www.openoffice.org/sc/excelfileformat.pdf - CONTINUE

        byte[] data;

        ContinueRecord(byte[] data) {
            this.data = data;
        }

        public int getDataSize() {
            return data.length;
        }

        public short getSid() {
            return (short)0x003C;
        }

        public void serialize(LittleEndianOutput out) {
            out.write(data);
        }
    }
}
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