Image crop, Remove unwanted white portion of Image using Java

Question

Image crop, Remove unwanted white portion of Image using Java. How can we Remove unwanted white portion of Image using Java? I am having image which have plan white region, I want to remove that unused white part of Image apart from my useful main image using JAVA Code. you can get clear idea form below shown image. i need to perform this task using Java code.

Click here to view image

Answer 1

This is a (very) simple example of a brute force method. Basically, it walks the image until the color changes from the desired fill color

This is woefully inefficient. I had thought about using a divide and conquer approach, but I really don't have the time to flesh it out.

import java.awt.Color;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class Test {

    public static void main(String[] args) throws IOException {
        BufferedImage img = ImageIO.read(new File("/Users/swhitehead/Downloads/47hb1.png"));
        Rectangle bounds = getBounds(img, Color.WHITE);
        System.out.println(bounds);
        BufferedImage trimmed = img.getSubimage(bounds.x, bounds.y, bounds.width, bounds.height);
        JOptionPane.showMessageDialog(null, new JLabel(new ImageIcon(trimmed)));
    }

    public static Rectangle getBounds(BufferedImage img, Color fillColor) {
        int top = getYInset(img, 20, 0, 1, fillColor);
        int bottom = getYInset(img, 20, img.getHeight() - 1, -1, fillColor);
        int left = getXInset(img, 0, top, 1, fillColor);
        int right = getXInset(img, img.getWidth() - 1, top, -1, fillColor);

        return new Rectangle(left, top, right - left, bottom - top);
    }

    public static int getYInset(BufferedImage img, int x, int y, int step, Color fillColor) {
        while (new Color(img.getRGB(x, y), true).equals(fillColor)) {
            y += step;
        }
        return y;
    }

    public static int getXInset(BufferedImage img, int x, int y, int step, Color fillColor) {
        while (new Color(img.getRGB(x, y), true).equals(fillColor)) {
            x += step;
        }
        return x;
    }
}

Answer 2

You can use an image processing framework to make image manipulation more easy.

In the example below I used Marvin. My approach:

1. Use gray scale thresholding to separate the white pixels from the rest of the image.
2. Find the bounding-box of the black segment
3. Crop the original image using segment detected in previous step.

Input:

Output (board_cropped.png):

Source code:

import static marvin.MarvinPluginCollection.*;
import java.awt.Rectangle;
import marvin.image.MarvinImage;
import marvin.io.MarvinImageIO;

public class BoardSegmentation {

    public BoardSegmentation() {
        MarvinImage imageOriginal = MarvinImageIO.loadImage("./res/board.png");
        MarvinImage image = imageOriginal.clone();
        thresholding(image, 250);
        Rectangle rect = getBoundingBox(image);
        crop(imageOriginal, image, rect.x, rect.y, rect.width, rect.height);
        MarvinImageIO.saveImage(image, "./res/board_cropped.png");
    }
    public Rectangle getBoundingBox(MarvinImage image) {
        Rectangle r = new Rectangle();
        r.x = -1; r.y = -1; r.width = -1; r.height = -1;
        for(int y=0; y<image.getHeight(); y++) {
            for(int x=0; x<image.getWidth(); x++) {
                if(image.getIntColor(x, y) == 0xFF000000) {
                    if(r.x == -1 || x < r.x) {  r.x = x;    }
                    if(r.width == -1 || x > r.x + r.width) {    r.width = x - r.x;  }
                    if(r.y == -1 || x < r.y) {  r.y = y;    }
                    if(r.height == -1 || y > r.y + r.height) {  r.height = y - r.y; }
                }
            }
        }
        return r;
    }
    public static void main(String[] args) {
        new BoardSegmentation();
    }
}