Main.java

package com.olegchir.bpmscan;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.*;
import java.util.List;

public class Main {

    public static void main(String[] args) {
        String infile = "C:\\temp\\sunset.bmp";
        String outfile = "C:\\temp\\results2.txt";
        BufferedImage bmp = null;
        try {
            File file = new File(infile);
            System.out.println(file.exists() ? "File exists" : "File not found");
            bmp = ImageIO.read(file);
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }

        HashMap<Integer, Integer> counters = new HashMap<>();
        List<Integer> colorList = new ArrayList<>();

        try (PrintWriter pw = new PrintWriter(new FileWriter(outfile))) {
            for (int y = 0; y < bmp.getHeight(); y++) {
                Color color = new Color(bmp.getRGB(640, y));
                pw.printf("%d -> [%d, %d, %d]\n", y, color.getRed(), color.getGreen(), color.getBlue());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

        public static void main2(String[] args) {
        String infile = "C:\\temp\\sunset.bmp";
        String outfile = "C:\\temp\\results.txt";
        BufferedImage bmp = null;
        try {
            File file = new File(infile);
            System.out.println(file.exists() ? "File exists" : "File not found");
            bmp = ImageIO.read(file);
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }

        HashMap<Integer, Integer> counters = new HashMap<>();

        for (int x = 0; x < bmp.getWidth(); x++) {
            for (int y = 0; y < bmp.getHeight(); y++) {
                Integer rgb = bmp.getRGB(x, y);
                Integer oldValue = counters.get(rgb);
                if (null == oldValue) {
                    counters.put(rgb, 1);
                } else {
                    counters.put(rgb, ++oldValue);
                }
            }
        }

        Map<Integer, Integer> sortedCounters = sortByComparator(counters, false);

        int allPixels = 0;
        File outf = new File(outfile);
        if (outf.exists()) {
            boolean delete = outf.delete();
        }
        try (PrintWriter pw = new PrintWriter(new FileWriter(outfile))) {
            for (Map.Entry<Integer, Integer> entry : sortedCounters.entrySet()) {
                Color color = new Color(entry.getKey());
                int num = entry.getValue();
                pw.printf("[%d, %d, %d] -> %d\n", color.getRed(), color.getGreen(), color.getBlue(), num);
                allPixels += num;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        System.out.println(allPixels);
    }

    private static Map<Integer, Integer> sortByComparator(Map<Integer, Integer> unsortMap, final boolean order) {

        List<Map.Entry<Integer, Integer>> list = new LinkedList<>(unsortMap.entrySet());

        // Sorting the list based on values
        Collections.sort(list, (o1, o2) -> {
            if (order) {
                return o1.getValue().compareTo(o2.getValue());
            } else {
                return o2.getValue().compareTo(o1.getValue());
            }
        });

        Map<Integer, Integer> sortedMap = new LinkedHashMap<>();
        for (Map.Entry<Integer, Integer> entry : list) {
            sortedMap.put(entry.getKey(), entry.getValue());
        }

        return sortedMap;
    }

}