How to convert a jpeg file into a 1-bit bmp file (2 colors image)

Question

Hi. I�m having serious problems to convert a jpeg file into a 1-bit bmp file (2 colors image).
I�m using FileSaver.saveAsBmp(String t) but what i get is a bmp image, but with 16M colors, but what i want is a 2 colors bmp file. A black and white image.
Does anybody know how to do this? I�m really getting crazy with ths problem.
Thanks in advance

Answer 1

Hi opalo,
this code may help you...
import java.awt.*;
import java.io.*;
import java.awt.image.*;
import javax.imageio.ImageIO;
class Write1 extends Component {
//--- Private constants
private final static int BITMAPFILEHEADER_SIZE = 14;
private final static int BITMAPINFOHEADER_SIZE = 40;
//--- Private variable declaration
//--- Bitmap file header
private byte bitmapFileHeader [] = new byte [14];
private byte bfType [] = {'B', 'M'};
private int bfSize = 0;
private int bfReserved1 = 0;
private int bfReserved2 = 0;
private int bfOffBits = BITMAPFILEHEADER_SIZE + BITMAPINFOHEADER_SIZE;
//--- Bitmap info header
private byte bitmapInfoHeader [] = new byte [40];
private int biSize = BITMAPINFOHEADER_SIZE;
private int biWidth = 50;
private int biHeight = 70;
private int biPlanes = 1;
//private int biBitCount = 24;
private int biBitCount = 1;
private int biCompression = 0;
private int biSizeImage = 0x030000;
private int biXPelsPerMeter = 0x0;
private int biYPelsPerMeter = 0x0;
private int biClrUsed = 0;
private int biClrImportant = 0;
//--- Bitmap raw data
private int bitmap [];
//--- File section
private FileOutputStream fo;
//--- Default constructor
public Write1() {
public void saveBitmap (String parFilename, Image parImage, int
parWidth, int parHeight) {
try {
fo = new FileOutputStream (parFilename);
save (parImage, parWidth, parHeight);
fo.close ();
catch (Exception saveEx) {
saveEx.printStackTrace ();
* The saveMethod is the main method of the process. This method
* will call the convertImage method to convert the memory image to
* a byte array; method writeBitmapFileHeader creates and writes
* the bitmap file header; writeBitmapInfoHeader creates the
* information header; and writeBitmap writes the image.
private void save (Image parImage, int parWidth, int parHeight) {
try {
convertImage (parImage, parWidth, parHeight);
writeBitmapFileHeader ();
writeBitmapInfoHeader ();
writeBitmap ();
catch (Exception saveEx) {
saveEx.printStackTrace ();
* convertImage converts the memory image to the bitmap format (BRG).
* It also computes some information for the bitmap info header.
private boolean convertImage (Image parImage, int parWidth, int parHeight) {
int pad;
bitmap = new int [parWidth * parHeight];
PixelGrabber pg = new PixelGrabber (parImage, 0, 0, parWidth, parHeight,
bitmap, 0, parWidth);
try {
pg.grabPixels ();
catch (InterruptedException e) {
e.printStackTrace ();
return (false);
pad = (4 - ((parWidth * 3) % 4)) * parHeight;
biSizeImage = ((parWidth * parHeight) * 3) + pad;
bfSize = biSizeImage + BITMAPFILEHEADER_SIZE +
BITMAPINFOHEADER_SIZE;
biWidth = parWidth;
biHeight = parHeight;
return (true);
* writeBitmap converts the image returned from the pixel grabber to
* the format required. Remember: scan lines are inverted in
* a bitmap file!
* Each scan line must be padded to an even 4-byte boundary.
private void writeBitmap () {
int size;
int value;
int j;
int i;
int rowCount;
int rowIndex;
int lastRowIndex;
int pad;
int padCount;
byte rgb [] = new byte [3];
size = (biWidth * biHeight) - 1;
pad = 4 - ((biWidth * 3) % 4);
if (pad == 4) // <==== Bug correction
pad = 0; // <==== Bug correction
rowCount = 1;
padCount = 0;
rowIndex = size - biWidth;
lastRowIndex = rowIndex;
try {
for (j = 0; j < size; j++) {
value = bitmap [rowIndex];
rgb [0] = (byte) (value & 0xFF);
rgb [1] = (byte) ((value >> 8) & 0xFF);
rgb [2] = (byte) ((value >> 16) & 0xFF);
fo.write (rgb);
if (rowCount == biWidth) {
padCount += pad;
for (i = 1; i <= pad; i++) {
fo.write (0x00);
int b = 1200;
fo.write(b);
rowCount = 1;
rowIndex = lastRowIndex - biWidth;
lastRowIndex = rowIndex;
else
rowCount++;
rowIndex++;
//--- Update the size of the file
bfSize += padCount - pad;
biSizeImage += padCount - pad;
catch (Exception wb) {
wb.printStackTrace ();
* writeBitmapFileHeader writes the bitmap file header to the file.
private void writeBitmapFileHeader () {
try {
fo.write (bfType);
fo.write (intToDWord (bfSize));
fo.write (intToWord (bfReserved1));
fo.write (intToWord (bfReserved2));
fo.write (intToDWord (bfOffBits));
catch (Exception wbfh) {
wbfh.printStackTrace ();
* writeBitmapInfoHeader writes the bitmap information header
* to the file.
private void writeBitmapInfoHeader () {
try {
fo.write (intToDWord (biSize));
fo.write (intToDWord (biWidth));
fo.write (intToDWord (biHeight));
fo.write (intToWord (biPlanes));
fo.write (intToWord (biBitCount));
fo.write (intToDWord (biCompression));
fo.write (intToDWord (biSizeImage));
fo.write (intToDWord (biXPelsPerMeter));
fo.write (intToDWord (biYPelsPerMeter));
fo.write (intToDWord (biClrUsed));
fo.write (intToDWord (biClrImportant));
// DataOutputStream temp = new DataOutputStream(fo);
// int m = 32;
// temp.writeInt(m);
catch (Exception wbih) {
wbih.printStackTrace ();
* intToWord converts an int to a word, where the return
* value is stored in a 2-byte array.
private byte [] intToWord (int parValue) {
byte retValue [] = new byte [2];
retValue [0] = (byte) (parValue & 0x00FF);
retValue [1] = (byte) ((parValue >> 8) & 0x00FF);
return (retValue);
* intToDWord converts an int to a double word, where the return
* value is stored in a 4-byte array.
private byte [] intToDWord (int parValue) {
byte retValue [] = new byte [4];
retValue [0] = (byte) (parValue & 0x00FF);
retValue [1] = (byte) ((parValue >> 8) & 0x000000FF);
retValue [2] = (byte) ((parValue >> 16) & 0x000000FF);
retValue [3] = (byte) ((parValue >> 24) & 0x000000FF);
return (retValue);
class Writebmp
     public static void main(String args[])
          //Image img = Toolkit.getDefaultToolkit().getImage("jatin.bmp");
          try
          File filename = new File("jatin_test.bmp");
          BufferedImage image = ImageIO.read(filename);
          Graphics graphics = image.getGraphics();
          graphics.drawString("&#2313;&#2332;&#2327;&#2352;",10,30);
          Write1 w = new Write1();
          Image img = Toolkit.getDefaultToolkit().getImage("jatin_test.bmp");
          w.saveBitmap("jatin_test.bmp",img,200,200);
          catch (IOException e)
System.err.println ("Unable to write to file");
System.exit(-1);
}