BMP width and height, BinaryReader Learn programming Java



Lesson:

File Management


Exercise:

BMP width and height, BinaryReader


Objetive:

Create a java program to display the width and height of a BMP file using a BinaryReader.

The structure of the header of a BMP file is:

File type (letters BM) at positions 0-1.
File size at positions 2-5.
Reserved at positions 6-7.
Reserved at positions 8-9.
Start of image data at positions 10-13.
Size of bitmap header at positions 14-17.
Width (pixels) at positions 18-21.
Height (pixels) at positions 22-25.
Number of planes at positions 26-27.
Size of each point at positions 28-29.
Compression (0=not compressed) at positions 30-33.
Image size at positions 34-37.
Horizontal resolution at positions 38-41.
Vertical resolution at positions 42-45.
Size of color table at positions 46-49.


Code:

public class Main
{
	public static void main(String[] args)
	{
		BinaryReader myFile;
		byte b1, b2;
		int width, height;

		myFile = new BinaryReader(File.Open("example.bmp", FileMode.Open));
		b1 = myFile.ReadByte();
		b2 = myFile.ReadByte();

		if ((b1 == 0x42) && (b2 == 0x4D))
		{
			System.out.println("It seems to be a BMP file");
			myFile.BaseStream.Seek(18, SeekOrigin.Begin);
			width = myFile.ReadInt32();
			height = myFile.ReadInt32();
			System.out.printf("Width: %1$s pixels" + "\r\n", width);
			System.out.printf("Height: %1$s pixels" + "\r\n", height);
		}
		else
		{
			System.out.println("It DOES NOT seem to be a BMP file");
		}

		myFile.Close();
	}
}



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