How to Double BMP file

Question

it is needed to create a new BMP file exactly twice the height of an original BMP file(which is uncompressed), and consisting of two copies of the original image, one on top of the other .
now I have modify the file size (ie. size of the bit map data+file size); doule the vaule of height, bit map data size, and calculate where the bit map data section stats(ie.the bit map data offset info)
But now I am not sure hwo to duplicate the entirebit map data section, then how to useFileout putStream and write() method to create a new double BMP file
Can anyone give me an example? Many thx.
My code is following:
import java.io.*;
public class BMPDouble {
     public static void main(String[] args) throws IOException{
          File bmp= new File(args[0]);
          getBMPInfo(bmp);
     public static void getBMPInfo(File f) throws IOException {
          FileInputStream fis= new FileInputStream(f);
               int bflen=14;  // 14 byte BITMAPFILEHEADER
              byte bf[]=new byte[bflen];
              fis.read(bf,0,bflen);
              int bilen=40; // 40-byte BITMAPINFOHEADER
              byte bi[]=new byte[bilen];
              fis.read(bi,0,bilen);
              int nsize = (((int)bf[5]&0xff)<<24)
                              | (((int)bf[4]&0xff)<<16)
                              | (((int)bf[3]&0xff)<<8)
                              | (int)bf[2]&0xff;
              int nheight = (((int)bi[11]&0xff)<<24)
                              | (((int)bi[10]&0xff)<<16)
                              | (((int)bi[9]&0xff)<<8)
                              | (int)bi[8]&0xff;
               int bmdsize = (((int)bi[23]&0xff)<<24)
                              | (((int)bi[22]&0xff)<<16)
                              | (((int)bi[21]&0xff)<<8)
                              | (int)bi[20]&0xff;
               int offsetInfo = (((int)bf[13]&0xff)<<24)
                              | (((int)bf[12]&0xff)<<16)
                              | (((int)bf[11]&0xff)<<8)
                              | (int)bf[10]&0xff;
               int newSize = nsize+bmdsize;
               int newHeight = nheight*2;
               int newBmdSize = bmdsize*2;
               System.out.println("Size: "+newSize+" bytes");
               System.out.println("Height: "+newHeight);
               System.out.println("Bit Map Data Size: "+newBmdSize);
               System.out.println("Bit Map Data offset: "+offsetInfo);
               fis.close();

Answer 1

thank you for code above, since it has some errors, so I change a little.
but I am not sure why in incomeData arrary should be 256. ie.byte[ ] incomeData = new byte[256];
whether it is also 14 bytes in new bit map file header and the rest is (256-14) bytes in new bit map info header? Please help me,thx.
My code is now following:
import java.io.*;
public class BMPDouble {
     public static void main(String[] args) throws IOException{
          File bmp= new File(args[0]);
          File bmpDouble= new File(args[1]);
          getBMPInfo(bmp);
          getBMPInfo(bmpDouble);
     public static void getBMPInfo(File f) throws IOException {
          FileInputStream fis= new FileInputStream(f);
          FileOutputStream fos= new FileOutputStream(f);
               int bflen=14;  // 14-byte BITMAPFILEHEADER
              byte bf[]=new byte[bflen];
              fis.read(bf,0,bflen);
              int bilen=40; // 40-byte BITMAPINFOHEADER
              byte bi[]=new byte[bilen];
              fis.read(bi,0,bilen);
              int nsize = (((int)bf[5]&0xff)<<24)
                              | (((int)bf[4]&0xff)<<16)
                              | (((int)bf[3]&0xff)<<8)
                              | (int)bf[2]&0xff;
              int nheight = (((int)bi[11]&0xff)<<24)
                              | (((int)bi[10]&0xff)<<16)
                              | (((int)bi[9]&0xff)<<8)
                              | (int)bi[8]&0xff;
               int bmdsize = (((int)bi[23]&0xff)<<24)
                              | (((int)bi[22]&0xff)<<16)
                              | (((int)bi[21]&0xff)<<8)
                              | (int)bi[20]&0xff;
               int offsetInfo = (((int)bf[13]&0xff)<<24)
                              | (((int)bf[12]&0xff)<<16)
                              | (((int)bf[11]&0xff)<<8)
                              | (int)bf[10]&0xff;
               int newSize = nsize+bmdsize;
               int newHeight = nheight*2;
               int newBmdSize = bmdsize*2;
               System.out.println("Size: "+newSize+" bytes");
               System.out.println("Height: "+newHeight);
               System.out.println("Bit Map Data Size: "+newBmdSize);
               System.out.println("Bit Map Data offset: "+offsetInfo);
               byte[] incomeData = new byte[256];
               int bytesRead;
               fos.write(NEWBITMAPFILEHEADER,0,NEWBITMAPFILEHEADER.length);
               fos.write(NEWBITMAPINFOHEADER,0,NEWBITMAPINFOHEADER.length);
               while((bytesRead=fis.read(incomeData))!= -1){
                    fos.write(incomeData,0,incomeData.length);
               fis.reset();
               while((bytesRead=fis.read(incomeData)) != -1){    
                    fos.write(incomeData,0,incomeData.length);
               fos.flush();
               fos.close();
               fis.close();
}