Main.java

package fr.leroideskiwis.imageToText;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Scanner;

public class Main {

    private Scanner scanner = new Scanner(System.in);

    private Main() throws IOException {

        File file = readFile("Path : ", true);
        BufferedImage image = ImageIO.read(file);

        StringBuilder builder = new StringBuilder();

        for(int y = 0; y < image.getHeight(); y++){
            for(int x = 0; x < image.getWidth(); x++){

                if(image.getRGB(x,y) > new Color(128, 128, 128).getRGB())
                    builder.append(".");
                else
                    builder.append("x");

                builder.append(" ");
            }
            builder.append("\n");
        }

        System.out.println(builder.toString());

    }

    public static void main(String[] args) throws IOException {

        new Main();

    }

    public String readString(String string){
        System.out.print(string);
        String readed = scanner.nextLine();
        System.out.println();
        return readed;
    }

    public File readFile(String string, boolean needExists){
        File file;

        do{
            file = new File(readString(string));
        }while(needExists != file.exists());

        return file;
    }
}

Ascii art