Java Convert a greyscale and sepia version of an image with BufferedImage

Question

I want to read an image and convert and output the original image, a greyscale version, and a sepia version. I am having trouble with the conversion, not very familiar with

Answer 1

You can create a filter interface for code reuse.

FilterApp

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

public class FilterApp {
    public static ClassLoader loader = FilterApp.class.getClassLoader();
    public static String outputDir = "build";

    public static void main(String[] args) {
        try {
            BufferedImage srcImage = loadImage("lobster.jpg");
            File dir = new File(outputDir);

            if (!dir.exists()) {
                dir.mkdirs();
            }

            for (FilterType filter : FilterType.values()) {
                BufferedImage filteredImage = filter.applyFilter(srcImage);
                String filename = String.format("%s/lobster_%s", outputDir, filter.name().toLowerCase());
                writeImage(filteredImage, filename, "jpg");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static BufferedImage loadImage(String filename) throws IOException {
        return ImageIO.read(loader.getResourceAsStream("resources/" + filename));
    }

    private static void writeImage(BufferedImage image, String filename, String ext) throws IOException {
        ImageIO.write(image, ext, new File(filename + '.' + ext));
    }
}

FilterType

import java.awt.image.BufferedImage;

import filter.GreyscaleFilter;
import filter.ImageFilter;
import filter.InvertFilter;
import filter.SepiaFilter;

public enum FilterType {
    GREYSCALE(new GreyscaleFilter()),
    INVERT(new InvertFilter()),
    SEPIA_10(new SepiaFilter(10));

    private ImageFilter filter;

    public ImageFilter getFilter() { return filter; }

    public BufferedImage applyFilter(BufferedImage img) {
        return this.filter.apply(img);
    }

    private FilterType(ImageFilter filter) {
        this.filter = filter;
    }
}

ImageFilter

package filter;

import java.awt.image.BufferedImage;

/** Common Interface for different filters. */ 
public interface ImageFilter {
    public BufferedImage apply(BufferedImage img);
}

GreyscaleFilter

package filter;

import java.awt.color.ColorSpace;
import java.awt.image.BufferedImage;
import java.awt.image.ColorConvertOp;

public class GreyscaleFilter implements ImageFilter {
    @Override
    public BufferedImage apply(BufferedImage img) {
        BufferedImage result = new BufferedImage(img.getWidth(), img.getHeight(), img.getType());
        ColorConvertOp op = new ColorConvertOp(ColorSpace.getInstance(ColorSpace.CS_GRAY), null);

        op.filter(img, result);

        return result;
    }
}

InvertFilter

package filter;

import java.awt.Color;
import java.awt.image.BufferedImage;

public class InvertFilter implements ImageFilter {
    @Override
    public BufferedImage apply(BufferedImage img) {
        BufferedImage result = new BufferedImage(img.getWidth(), img.getHeight(), img.getType());

        for (int x = 0; x < img.getWidth(); x++) {
            for (int y = 0; y < img.getHeight(); y++) {
                int rgb = img.getRGB(x, y);
                Color color = new Color(rgb, true);
                int r = 255 - color.getRed();
                int g = 255 - color.getGreen();
                int b = 255 - color.getBlue();

                color = new Color(r, g, b, color.getAlpha());
                result.setRGB(x, y, color.getRGB());
            }
        }

        return result;
    }
}

SepiaFilter

package filter;

import java.awt.Color;
import java.awt.image.BufferedImage;

// Algorithm obtained from http://stackoverflow.com/questions/21899824
public class SepiaFilter implements ImageFilter {
    private int intensity;

    public void setIntensity(int intensity) { this.intensity = intensity; }
    public int getIntensity() { return intensity; }

    public SepiaFilter(int intensity) {
        this.intensity = intensity;
    }

    @Override
    public BufferedImage apply(BufferedImage img) {
        BufferedImage result = new BufferedImage(img.getWidth(), img.getHeight(), img.getType());
        // Play around with this.
        // 20 works well and was recommended by another developer.
        // 0 produces black/white image
        int sepiaDepth = 20;

        int w = img.getWidth();
        int h = img.getHeight();

        // We need 3 integers (for R,G,B color values) per pixel.
        int[] pixels = new int[w * h * 3];
        img.getRaster().getPixels(0, 0, w, h, pixels);

        for (int x = 0; x < img.getWidth(); x++) {
            for (int y = 0; y < img.getHeight(); y++) {
                int rgb = img.getRGB(x, y);
                Color color = new Color(rgb, true);
                int r = color.getRed();
                int g = color.getGreen();
                int b = color.getBlue();
                int gry = (r + g + b) / 3;

                r = g = b = gry;
                r = r + (sepiaDepth * 2);
                g = g + sepiaDepth;

                if (r > 255) { r = 255; }
                if (g > 255) { g = 255; }
                if (b > 255) { b = 255; }

                // Darken blue color to increase sepia effect
                b -= this.intensity;

                // normalize if out of bounds
                if (b < 0)   { b = 0; }
                if (b > 255) { b = 255; }

                color = new Color(r, g, b, color.getAlpha());
                result.setRGB(x, y, color.getRGB());
            }
        }

        return result;
    }
}

Output

Source Image

Generated Images