问题
I am trying to find the vertices and their coordinates for simple geometric shape using marvin-framework.
This is the code I have (based on https://stackoverflow.com/a/25223830/957057)
package com.example.marvin;
import static marvin.MarvinPluginCollection.floodfillSegmentation;
import static marvin.MarvinPluginCollection.moravec;
import static marvin.MarvinPluginCollection.scale;
import java.io.FileWriter;
import java.io.IOException;
import marvin.image.MarvinImage;
import marvin.image.MarvinSegment;
import marvin.io.MarvinImageIO;
public class ShapesExample {
private FileWriter fw = null;
public ShapesExample() throws IOException{
fw = new FileWriter("out.txt");
// Scale down the image since the desired features can be extracted
// in a lower resolution.
MarvinImage image = MarvinImageIO.loadImage("square.png");
scale(image.clone(), image, 269);
// segment each object
MarvinSegment[] objs = floodfillSegmentation(image);
MarvinSegment seg;
OUT("Number of objects: " + objs.length);
// For each object...
// Skip position 0 which is just the background
for(int i=1; i<objs.length; i++){
seg = objs[i];
OUT("seq: " + seg);
MarvinImage imgSeg = image.subimage(seg.x1-5, seg.y1-5, seg.width+10, seg.height+10);
OUT("i = " + i + "/" + objs.length);
int[][] output;
output = moravec(imgSeg, null, 18, 1000000);
int xcount = 0;
for(int x = 0; x < output.length; x++) {
OUT("x = " + xcount++ + "/" + output[x].length);
for(int y = 0; y < output[y].length; y++) {
OUTNONL("y = " + output[x][y] + " ");
}
OUT("");
}
}
fw.close();
}
private void OUTNONL(String str) throws IOException {
System.out.print(str);
}
private void OUT(String str) throws IOException {
System.out.println(str);
}
public static void main(String[] args) throws IOException {
new ShapesExample();
}
}
square.png contains the shape image
This is the output I see:
Number of objects: 3
seq: {x1:97, x2:136, y1:35, y2:72, width:40, height:38, area:189}
i = 1/3
x = 0/48
y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0
.....
x = 48/48
y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0
seq: {x1:99, x2:135, y1:36, y2:71, width:37, height:36, area:1333}
i = 2/3
x = 0/46
y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0
.....
x = 46/46
y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0 y = 0
(where i is nth object detected in image, x is row, y is column) As you can see all values are 0.
Question:
- what am i missing in getting the coordinates?
- why does it detect 3 shapes in the image?
回答1:
"why does it detect 3 shapes in the image?"
FloodfillSegmentation fill areas of pixels having distinct colors. In your case there are three separated areas: (1) white background, (2) square lines, (3) square interior. To solve this, I simply transformed your square in a solid shape:
boundaryFill(image.clone(), image, 1, 1, Color.BLACK);
invertColors(image);
"what am i missing in getting the coordinates?"
The moravec output is not a list of vertices. It's a map of pixels having an intensity value related to corners positions. I added getVertices(int[][] cornernessMap, int minDistanceBetweenPoints) method to your application in order to get the correct position of the vertices.
SOLUTION
output image:
output text:
Number of objects: 1
Vertex: (147,54)
Vertex: (147,105)
Vertex: (200,54)
Vertex: (200,105)
source code:
import static marvin.MarvinPluginCollection.boundaryFill;
import static marvin.MarvinPluginCollection.floodfillSegmentation;
import static marvin.MarvinPluginCollection.invertColors;
import static marvin.MarvinPluginCollection.moravec;
import static marvin.MarvinPluginCollection.scale;
import java.awt.Color;
import java.awt.Point;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import marvin.image.MarvinImage;
import marvin.image.MarvinSegment;
import marvin.io.MarvinImageIO;
public class ShapesExample {
private FileWriter fw = null;
public ShapesExample() throws IOException{
fw = new FileWriter("out.txt");
// Scale down the image since the desired features can be extracted
// in a lower resolution.
MarvinImage image = MarvinImageIO.loadImage("./res/square.png");
scale(image.clone(), image, 400);
// Transform the square in a solid shape
boundaryFill(image.clone(), image, 1, 1, Color.BLACK);
invertColors(image);
MarvinImageIO.saveImage(image, "./res/square_2.png");
// segment each object
MarvinSegment[] objs = floodfillSegmentation(image);
MarvinSegment seg;
OUT("Number of objects: " + (objs.length-1));
int MATRIX_SIZE = 5;
// For each object...
// Skip position 0 which is just the background
for(int i=1; i<objs.length; i++){
seg = objs[i];
int[][] output = moravec(image, null, MATRIX_SIZE, 1000);
List<Point> vertices = getVertices(output, 10);
// Draw the vertices and print coordinates
for(Point p:vertices) {
image.fillRect(p.x-(MATRIX_SIZE/2), p.y-(MATRIX_SIZE/2), 5, 5, Color.red);
OUT("Vertex: ("+p.x+","+p.y+")");
}
}
MarvinImageIO.saveImage(image, "./res/square_out.png");
fw.close();
}
private List<Point> getVertices(int[][] cornernessMap, int minDistanceBetweenPoints){
int corners=0;
List<Point> points = new ArrayList<Point>();
for(int x=0; x<cornernessMap.length; x++){
for(int y=0; y<cornernessMap[0].length; y++){
// Is it a corner?
if(cornernessMap[x][y] > 0){
// This part of the algorithm avoid inexistent corners
// detected almost in the same position due to noise.
Point newPoint = new Point(x,y);
if(points.size() == 0){
points.add(newPoint); corners++;
}else {
boolean valid=true;
for(Point p:points){
if(newPoint.distance(p) < minDistanceBetweenPoints){
valid=false;
}
}
if(valid){
points.add(newPoint); corners++;
}
}
}
}
}
return points;
}
private void OUTNONL(String str) throws IOException {
System.out.print(str);
}
private void OUT(String str) throws IOException {
System.out.println(str);
}
public static void main(String[] args) throws IOException {
new ShapesExample();
}
}
来源：https://stackoverflow.com/questions/52549493/2d-geometric-shape-vertices-coordinates-detection