Edit: Updated the code, the code below now correctly draws rectangles around multiple shapes, but still has a minor issue of sometimes creating multiple rectangles on one single shape.
I have 2 Images, that i compare pixel by pixel with each other and i want my programm to create rectangles around the area of difference (multiple rectangles with multiple instances of differences). So far i managed to do this with a single rectangle, so if i had multiple "instances", they'd all be in one big rectangle. Now i'm trying to make the programm create multiple rectangles, but run into an IndexOutOfBoundsException.
The Programm itself overlays the 2 Images being compared with opacity and outputs the resulting overlaid image along with the rectangles into a new File. Both Images being compared have a consistent equal width and height.
I'm calling the rectangles i want to be drawn "regions" within the code. The Region List is being continiously updated while the comparison is running.
The first question i asked myself was, when does a point of difference (pixel difference) belong to a region? My attempt was to define a "tolerance", so as long as the pixel being compared is within the tolerance of the last found point of difference, it belongs to the same region. I quickly realized that this doesn't work as soon as i have a shape in form of a giant U on my image, with the top points being far enough apart to be not within the tolerance. And now i'm kind-of stuck, because i feel like i'm on the wrong path.
Below is the code i have so far:
private void compareImages() throws IOException{
BufferedImage img1;
BufferedImage img2;
try {
img1 = ImageIO.read(new File(path_to_img1));
img2 = ImageIO.read(new File(path_to_img2));
} catch (Throwable e) {
System.out.println("Unable to load the Images!");
return;
}
BufferedImage dest = new BufferedImage(img1.getWidth(), img1.getHeight(), BufferedImage.TYPE_INT_ARGB);
Graphics2D gfx = dest.createGraphics();
gfx.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.65f));
//Compare Images pixel by pixel
int sX = 9999; //Start X
int sY = 9999; //Start Y
int eX = 0; //End X
int eY = 0; //End Y
boolean isDrawable = false;
boolean loadedRegion = false;
List<Rectangle> regions = new ArrayList<>();
List<Rectangle> check_regions = new ArrayList<>();
Rectangle tmp_comparison;
int regionID = 0;
int tolerance = 25;
for (int i = 0; i < img1.getHeight(); i++) {
for (int j = 0; j < img1.getWidth(); j++) {
loadedRegion = false;
regionID = 0;
sX = 9999;
sY = 9999;
eX = 0;
eY = 0;
if ( img1.getRGB(j, i) != img2.getRGB(j, i) ){
isDrawable = true;
if (regions.size() != 0){
//Attempting to locate a matching existing Region
tmp_comparison = new Rectangle(j, i, 1, 1);
for (int trID = 0; trID<regions.size(); trID++){
if (tmp_comparison.intersects(check_regions.get(trID).getBounds()) == true) {
// Region found
sX = (int) regions.get(trID).getX();
sY = (int) regions.get(trID).getY();
eX = (int) regions.get(trID).getWidth();
eY = (int) regions.get(trID).getHeight();
regionID = trID;
loadedRegion = true;
break;
}
}
}
//Update Region Dimension
if (j<sX){
sX = j;
}
if (j>eX){
eX = j;
}
if (i<sY){
sY = i;
}
if (i>eY){
eY = i;
}
if (regions.size() == 0 || loadedRegion == false){
regions.add(new Rectangle(sX, sY, eX, eY));
check_regions.add(new Rectangle(sX-tolerance, sY-tolerance, eX-sX+(tolerance*2), eY-sY+(tolerance*2)));
} else {
regions.set(regionID, new Rectangle(sX, sY, eX, eY));
check_regions.set(regionID, new Rectangle(sX-tolerance, sY-tolerance, eX-sX+(tolerance*2), eY-sY+(tolerance*2)));
}
}
}
}
// If there are any differences, draw the Regions
// Regions are 10px bigger in all directions as compared to the actual rectangles of difference
if (isDrawable == true){
gfx.setPaint(Color.red);
for (int i = 0; i<regions.size(); i++) {
int dsX = 0;
int dsY = 0;
int deX = 0;
int deY = 0;
sX = (int) regions.get(i).getX();
sY = (int) regions.get(i).getY();
eX = (int) regions.get(i).getWidth();
eY = (int) regions.get(i).getHeight();
if (sX>=10){dsX = sX-10;}
if (eX<=img1.getWidth()-10){deX = eX-sX+20;}
if (sY>=10){dsY = sY-10;}
if (eY<=img1.getHeight()-10){deY = eY-sY+20;}
gfx.draw(new Rectangle2D.Double(dsX, dsY, deX, deY));
}
}
gfx.drawImage(img1, 0, 0, null);
gfx.drawImage(img2, 0, 0, null);
gfx.dispose();
File out = new File("C:\\output.png");
ImageIO.write(dest, "PNG", out);
}
Below is the code that creates one big rectangle around all the differences found in the images being compared.
private void oneRectangle() throws IOException{
BufferedImage img1;
BufferedImage img2;
try {
img1 = ImageIO.read(new File(path_to_img1));
img2 = ImageIO.read(new File(path_to_img2));
} catch (Throwable e) {
System.out.println("Unable to load the Images!");
return;
}
BufferedImage dest = new BufferedImage(img1.getWidth(), img1.getHeight(), BufferedImage.TYPE_INT_ARGB);
Graphics2D gfx = dest.createGraphics();
gfx.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.65f));
//Compare Images pixel by pixel
boolean isDrawable = false;
int sX = 9999;
int sY = 9999;
int eX = 0;
int eY = 0;
for (int i = 0; i < img1.getHeight(); i++) {
for (int j = 0; j < img1.getWidth(); j++) {
if ( img1.getRGB(j, i) != img2.getRGB(j, i) ){
isDrawable = true;
if (j<sX){
sX = j;
}
if (j>eX){
eX = j;
}
if (i<sY){
sY = i;
}
if (i>eY){
eY = i;
}
}
}
}
// Draw rectangle if there are any differences
if (isDrawable == true){
gfx.setPaint(Color.red);
int dsX = 0;
int dsY = 0;
int deX = 0;
int deY = 0;
if (sX>=10){dsX = sX-10;}
if (eX<=img1.getWidth()-10){deX = eX-sX+20;}
if (sY>=10){dsY = sY-10;}
if (eY<=img1.getHeight()-10){deY = eY-sY+20;}
gfx.fill(new Rectangle2D.Double(dsX, dsY, deX, deY));
}
gfx.drawImage(img1, 0, 0, null);
gfx.drawImage(img2, 0, 0, null);
gfx.dispose();
File out = new File("C:\\output.png");
ImageIO.write(dest, "PNG", out);
}