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| import java.awt.FileDialog;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
/**
* Reduce the height of an image, using the minimum energy path method.
*
* (cf. "Content Aware Image Resizing" by Avidan, S. & Shamir, A.)
*
* @author Xavier Philippeau
*/
public class Carving {
// image current dimension
private int height=0, width=0;
// rgb image
private int[][] rgbimage = null;
// energy of each pixel
private int[][] energy = null;
// all possible (horizontal) path
private Path[] hpath = null;
// Path class
class Path {
// total energy
int energy=0;
// direction of path (-1,0,+1) for each pixel
int[] direction=null;
// min, max relative offsets
int lowestoffset=0,highestoffset=0;
}
/**
* Constructor
*
* @param bimg the image to resize
*/
public Carving(BufferedImage bimg) {
// initialize arrays
this.width = bimg.getWidth();
this.height = bimg.getHeight();
this.rgbimage = new int[width][height];
this.energy = new int[width][height];
this.hpath = new Path[height];
// convert BufferedImage in a 2d array
for (int y=0; y<height; y++)
for (int x=0; x<width; x++)
this.rgbimage[x][y] = bimg.getRGB(x, y);
}
/**
* @return the current image
*/
public BufferedImage getImage() {
BufferedImage bimg = new BufferedImage(this.width,this.height,BufferedImage.TYPE_INT_ARGB);
for (int y=0; y<height; y++)
for (int x=0; x<width; x++)
bimg.setRGB(x, y, this.rgbimage[x][y] );
return bimg;
}
/**
* compute energy array
*
* @param ymin y range start
* @param ymax y range end
*/
private void computeEnergy(int ymin, int ymax) {
for (int y=ymin; y<ymax; y++)
for (int x=0; x<width; x++)
energy[x][y]=gradient(x, y);
}
/**
* 8 neighbours gradient
*
* @param x x coord
* @param y y coord
* @return gradient norme
*/
private int gradient(int x, int y) {
// Coordinates of 8 neighbours
int px = x - 1; // previous x
int nx = x + 1; // next x
int py = y - 1; // previous y
int ny = y + 1; // next y
// limit to image dimension (spheric)
if (px < 0) px=this.width-1;
if (nx >= this.width) nx=0;
if (py < 0) py=this.height-1;
if (ny >= this.height) ny=0;
// Intensity of the 8 neighbours
int Ipp = getLuminance( this.rgbimage[px][py] );
int Icp = getLuminance( this.rgbimage[ x][py] );
int Inp = getLuminance( this.rgbimage[nx][py] );
int Ipc = getLuminance( this.rgbimage[px][ y] );
int Inc = getLuminance( this.rgbimage[nx][ y] );
int Ipn = getLuminance( this.rgbimage[px][ny] );
int Icn = getLuminance( this.rgbimage[ x][ny] );
int Inn = getLuminance( this.rgbimage[nx][ny] );
// Local gradient (sobel)
int gradx = (Inc-Ipc)*2 + (Inp-Ipp) + (Inn-Ipn);
int grady = (Icn-Icp)*2 + (Ipn-Ipp) + (Inn-Inp);
int norme = (int)Math.sqrt(gradx*gradx+grady*grady)/4;
return norme;
}
/**
* return luminance of a rgb value
*
* @param rgb value in ARGB format
* @return luminance
*/
private int getLuminance(int rgb) {
int r = (rgb >>16 ) & 0xFF;
int g = (rgb >> 8 ) & 0xFF;
int b = rgb & 0xFF;
int gray = (299*r + 587*g + 114*b)/1000;
return gray;
}
/**
* compute the horizontal path starting from left at y position = ystart
*
* @param ystart starting y position
*/
private void computeHorizontalPath(int ystart) {
// contruct a new path
Path path = new Path();
path.direction = new int[width];
// add/replace in the global list
this.hpath[ystart]=path;
// go from letf to right
int miny = Integer.MAX_VALUE, maxy = 0;
int y=ystart;
for (int x=0; x<width-1; x++) {
// update min/max absolute value
if (y<miny) miny=y;
if (y>maxy) maxy=y;
// update total energy of the path
int v = this.energy[x][y];
path.energy+=v;
// the 3 next possible positions for the current path
int vk_up=Integer.MAX_VALUE;
if (y>0) vk_up = this.energy[x+1][y-1];
int vk_center=Integer.MAX_VALUE;
vk_center = this.energy[x+1][y];
int vk_down=Integer.MAX_VALUE;
if (y<(height-1)) vk_down = this.energy[x+1][y+1];
// find the lowest energy for the 3 positions
int min = Math.min(vk_up,Math.min(vk_center,vk_down));
// follow the lowest energy direction
int dir=0;
if (min==vk_up) dir=-1;
if (min==vk_down) dir=+1;
if (min==vk_center) dir=0;
y+=dir;
// update path
path.direction[x]=dir;
}
path.lowestoffset = ystart-miny;
path.highestoffset = maxy-ystart;
}
/**
* @return the path index with minimum energy
*/
private int findBestHorizontalPath() {
int bestpathnumber=0;
int bestpathenergy=Integer.MAX_VALUE;
for (int ystart=0; ystart<height; ystart++) {
if (this.hpath[ystart].energy<bestpathenergy) {
bestpathenergy=this.hpath[ystart].energy;
bestpathnumber=ystart;
if (bestpathenergy==0) break;
}
}
return bestpathnumber;
}
/**
* Reduce the image height
*
* @param newheight new height of the image
* @param label0 display while computing (may be null)
*/
public void reduceHeight(int newheight, JLabel label0) {
// compute the whole energy
computeEnergy(0,this.height);
// compute all path
for (int y=0; y<height; y++)
computeHorizontalPath(y);
// reduce image, line by line
int hcount = this.height-newheight;
for(int hloop=0;hloop<hcount;hloop++) {
// find best path
int pathid = findBestHorizontalPath();
// construct absolute path
int[] bestpath = new int[hpath[pathid].direction.length];
int yabs=pathid;
for (int x=0; x<hpath[pathid].direction.length; x++) {
bestpath[x]=yabs;
yabs+=hpath[pathid].direction[x];
}
// optionnal: display current state
if (label0!=null && hloop%10 == 0) {
for (int x=0; x<hpath[pathid].direction.length; x++)
this.rgbimage[x][bestpath[x]]=0xF0F0F0;
label0.setIcon( new ImageIcon(this.getImage()) );
}
// construct the new image
for (int x=0; x<hpath[pathid].direction.length; x++) {
int y = bestpath[x];
// move up all elements of arrays below the path
int length = this.height-y-1;
System.arraycopy(this.energy[x], y+1, this.energy[x], y, length);
System.arraycopy(this.rgbimage[x], y+1, this.rgbimage[x], y, length);
// zeroing unused bottom part of arrays (not usefull)
this.energy[x][this.height-1]=0;
}
// highlevel/downlevel watermark of changed region
int ymin_changed=pathid-hpath[pathid].lowestoffset;
int ymax_changed=pathid+hpath[pathid].highestoffset;
// resize hpath array
int length = this.height-pathid-1;
System.arraycopy(this.hpath, pathid+1, this.hpath, pathid, length);
this.hpath[this.height-1]=null;
// resize the image
this.height--;
// optim: recompute only the energy for the changed region
int region_ymin = Math.max(ymin_changed-1, 0);
int region_ymax = Math.min(ymax_changed+1, this.height);
computeEnergy(region_ymin,region_ymax);
// optim: recompute only the path that go through the changed region
for (int y=0; y<height; y++) {
if ((y-this.hpath[y].lowestoffset)>ymax_changed) continue;
if ((y+this.hpath[y].highestoffset)<ymin_changed) continue;
computeHorizontalPath(y);
}
}
}
public static void main(String[] args) {
Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
JFrame frame = new JFrame("Demo - Divide height by 4 using minimum energy path");
JPanel panneau = new JPanel();
JLabel label0 = new JLabel();
panneau.add(label0);
frame.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
frame.getContentPane().add(new JScrollPane(panneau));
frame.pack();
frame.setVisible(true);
frame.setSize(800, 600);
FileDialog filedialog = new FileDialog(frame, "Choose an image file");
filedialog.setVisible(true);
String filename = filedialog.getFile();
String directory = filedialog.getDirectory();
File file = new File(directory+File.separator+filename);
try {
BufferedImage bimg = ImageIO.read(file);
Carving carve = new Carving(bimg);
carve.reduceHeight(bimg.getHeight() / 4, label0);
label0.setIcon(new ImageIcon(carve.getImage()));
} catch (IOException e) {
label0.setText(e.getMessage());
}
}
} |
