Thread: How do i make the .bmp image to be black/white ?

I have this small program

package fisiere;
 
import java.io.*;
import java.util.Scanner;
 
 
 
public class Fisieremain {
 
 
	public static void main(String[] args) {
 
 
 
 
		int B;
		int G;
		int R;
 
 
		try
		{
		BufferedInputStream fisier = new BufferedInputStream(new FileInputStream("pisica.bmp"));    //file i read bytes from
		BufferedOutputStream  fisier2 = new BufferedOutputStream (new FileOutputStream("C:/Users/npiulitza/Desktop/poza/poze2094.bmp"));    // here i write them
 
		for (int i =0; i<54; i++)
		{
			fisier2.write(fisier.read());    // here i copy the header of the file
		}
 
		while (true)
		{
			B = fisier.read();     // here i read values for each of the three colors     
			G = fisier.read();
			R = fisier.read();
 
			fisier2.write(B);     // and here i write them to second file
			if (B==-1)
				break;        // the bubble ends when there are no more bytes to read
			fisier2.write(G);
			fisier2.write(R);
 
 
		}
		fisier.close();
		fisier2.close();
 
		}
 
		catch (IOException e)
		{
			System.out.println(e);
		}
 
 
	}
}

In this program, i read from a .bmp files the blue, yellow and read color values for each pixel of the image. And, after write them as bytes to another .bmp file. It works, i could even manage to change colors little, if i make blue and yellow to be 0, the image will be red, but i wonder if there is any formula for obtaining a black/white image. Searched little on google but did not find something to help

Are you looking for an algorithm for converting pixels to either black or white?
Read a pixel and change its color to either 0x000000 or 0xFFFFFF

No, i do not need to use HTML colors. In my code, B is blue value (from 0 to 256) , G is yellow and R is red. And there where i write them to the file

fisier2.write(B); // and here i write them to second file
if (B==-1)
break; // the bubble ends when there are no more bytes to read
fisier2.write(G);
fisier2.write(R);

i need to sum or make an operation with these values. For example if i decrease each of them like this

fisier2.write(B-100); // and here i write them to second file
if (B==-1)
break; // the bubble ends when there are no more bytes to read
fisier2.write(G-100);
fisier2.write(R-100);

My picture will have negative colors. And i remember i heard some time ago it is a formula to make it black/white ( i think 2 of them need to be 0 for each pixel and one should have all the colors added or decreased or something)

Sorry, i have not ideas about the algorithms you mention.
If you only want black and white then you need to write either 0, 0, 0 or FF FF FF for the three bytes.

No, i do not want like that, i want the picture become as if it was taken with black/white camera, not that some pixels be pure black and others pure white, it should also have gray pixels. Well, i will search little more and will try discover the formula myself. And i am sure i have to mix somehow blue,red and yellow color intensities.

it should also have gray pixels

How do i make the .bmp image to be black/white ?

There is s contradiction here. B/W vs gray.

Hmm look mate, i have writen for every color

fisier2.write(B/2);
fisier2.write(B/2);
fisier2.write(B/2);

And the picture that was

Tom+y+Jerry.jpg


And, after it is
Tom+y+Jerry2.jpg

And...you do not say the second picture in black/white ?

I don't see any white in the second picture.