Read BMP File...

[Piri]

Hi all...I am a student and have to do a work in Java, and i'm kind off stuck :confused:

Hi need to read a binary file (in this case a BMP file) and later tell some things about the file and let the user flip and re-size the image! But first I need help to read the file :S

I now that a BMP File follows this structure:

Class Bitmap{
BitmapFileHeader bitmapFileHeader;
BitmapInfoHeader bitmapInfoHeader;
byte[] rgbQuad; // color pallete – opcional (ver abaixo)
byte[] data; // pixel data
}

Class BitmapFileHeader {
short type; // must be 'BM' to declare a bmp-file
int size; // specifies the size of the file in bytes
short reserved1; // must always be set to zero
short reserved2; // must always be set to zero
int offBits; // specifies the offset from the
// beginning of the file to the bitmap data
}

Class BitmapInfoHeader{
int size; // the size of this header (40 bytes)
int width; // the bitmap width in pixels
int height; // the bitmap height in pixels
short planes; // the number of color planes being used. Must be set to 1
short bitCount; // the number of bits per pixel (color depth) - 1, 4, 8, 16, 24, 32
int compression; // the compression method being used
int sizeImage; // the image size. This is the size of the raw bitmap data
int xPelsPerMeter; // the horizontal resolution of the image (pixel per meter)
int yPelsPerMeter; // the vertical resolution of the image (pixel per meter)
int clrUsed; // the number of colors in the color palette,
// or 0 to default to 2n
int clrImportant; // the number of important colors used,
// or 0 when every color is important
}
The teacher told that it was just read the file because after we now the structure the rest is easy -.-

I did the classes and started to read from the file...But when I get to read the byte[] data; something wrong appear...The compiler tells me that OffBits() is null -.-

I even now that I have to:
short bitCount = Short.reverseBytes(in.readShort());
int size = Integer.reverseBytes(in.readInt());
because:

(Least Significant Byte first).
Vrs
(Most Significant Byte first).

Here it goes part of my code:
public boolean addPicture(String local) throws IOException{
try{
File fileOrigin = new File(local);
FileInputStream i = new FileInputStream(fileOrigin);
DataInputStream in = new DataInputStream(i);


BitmapFileHeader parte1=new BitmapFileHeader();
parte1.setType(Short.reverseBytes(in.readShort())) ;
parte1.setSize(Integer.reverseBytes(in.readInt())) ;
parte1.setReserved1(Short.reverseBytes(in.readShor t()));
parte1.setReserved2(Short.reverseBytes(in.readShor t()));
parte1.setOffBits(Short.reverseBytes(in.readShort( )));


setBitmapFileHeader(parte1);

BitmapInfoHeader parte2=new BitmapInfoHeader();
parte2.setSize(Integer.reverseBytes(in.readInt())) ;
parte2.setWidth(Integer.reverseBytes(in.readInt()) );
parte2.setHeight(Integer.reverseBytes(in.readInt() ));
parte2.setPlanes(Short.reverseBytes(in.readShort() ));
parte2.setBitCount(Short.reverseBytes(in.readShort ()));
parte2.setCompression(Integer.reverseBytes(in.read Int()));
parte2.setSizeImage(Integer.reverseBytes(in.readIn t()));
parte2.setxPelsPerMeter(Integer.reverseBytes(in.re adInt()));
parte2.setyPelsPerMeter(Integer.reverseBytes(in.re adInt()));
parte2.setClrUsed(Integer.reverseBytes(in.readInt( )));

parte2.setClrImportant(Integer.reverseBytes(in.rea dInt()));

setBitmapInfoHeader(parte2);
//int x;
//while((x = in.read()) != -1){
//System.out.println("byte = "+x);
//}
//try{
System.out.println(parte1.getOffBits());
System.out.println(parte1.getType());
in.read(data,Integer.reverseBytes(parte1.getOffBit s()),1);



// }catch(java.lang.NullPointerException e){
// System.out.println("NILLLLLLL");
// }
System.out.println(getData());
in.close();
}catch(Exception e){
System.out.println("Error = "+e);
}

return true;
}

Hope that someone helps me :(

[JosAH]

Why not leave the actual reading of the .bmp file to the ImageIO class? Read the API documentation.

kind regards,

Jos

[Piri]

Because its suppose to read the file this way -.-

Aim is to develop an application that allows to decode and process the
content of an image file in BMP format (uncompressed). The application
must meet the following requirements:
a) Receive the location of a BMP file, open it and print all information
on that file, ie number of rows, columns, number of colors, etc..
b) allowing the extraction of pixel data "and save to a file." raw ". Try to visualize
this file with appropriate image viewer (Irfanview, Photoshop, etc.)
c) allow the reduction of the size of the image to ¼. For example, an image with
with 512x512 pixels would then be 256x256. The end result should be saved
a new BMP file.
d) Allow the image to reverse (flip) vertically or horizontally. The end result should
be stored in a new BMP file.

[Piri]

Can someone help me ? :confused: