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PCA in Processing for real time object orientation tracking
import Jama.Matrix;
import pca_transform.*;
import hypermedia.video.*;
PCA pca;
PVector axis1;
PVector axis2;
PVector mean;
OpenCV opencv;
PImage img;
int imgWidth = 640/4;
int imgHeight = 480/4;
PVector centroid;
void setup() {
size(640, 480);
opencv = new OpenCV(this);
opencv.capture(imgWidth, imgHeight);
centroid = new PVector();
}
Matrix toMatrix(PImage img) {
ArrayList<PVector> points = new ArrayList<PVector>();
for (int x = 0; x < img.width; x++) {
for (int y = 0; y < img.height; y++) {
int i = y*img.width + x;
if (brightness(img.pixels[i]) > 0) {
points.add(new PVector(x, y));
}
}
}
Matrix result = new Matrix(points.size(), 2);
float centerX = 0;
float centerY = 0;
for (int i = 0; i < points.size(); i++) {
result.set(i, 0, points.get(i).x);
result.set(i, 1, points.get(i).y);
centerX += points.get(i).x;
centerY += points.get(i).y;
}
centerX /= points.size();
centerY /= points.size();
centroid.x = centerX;
centroid.y = centerY;
return result;
}
void imageInGrid(PImage img, String message, int row, int col) {
int currX = col*img.width;
int currY = row*img.height;
image(img, currX, currY);
fill(255, 0, 0);
text(message, currX + 5, currY + imgHeight - 5);
}
void draw() {
background(125);
opencv.read();
opencv.convert(GRAY);
imageInGrid(opencv.image(), "GRAY", 0, 0);
opencv.absDiff();
imageInGrid(opencv.image(), "DIFF", 0, 1);
opencv.brightness(60);
imageInGrid(opencv.image(), "BRIGHTNESS: 60", 0, 2);
opencv.threshold(40);
imageInGrid(opencv.image(), "THRESHOLD: 40", 0, 3);
opencv.contrast(120);
imageInGrid(opencv.image(), "CONTRAST: 120", 1, 3);
Matrix m = toMatrix(opencv.image());
if (m.getRowDimension() > 0) {
pca = new PCA(m);
Matrix eigenVectors = pca.getEigenvectorsMatrix();
axis1 = new PVector();
axis2 = new PVector();
if (eigenVectors.getColumnDimension() > 1) {
axis1.x = (float)eigenVectors.get(0, 0);
axis1.y = (float)eigenVectors.get(1, 0);
axis2.x = (float)eigenVectors.get(0, 1);
axis2.y = (float)eigenVectors.get(1, 1);
axis1.mult((float)pca.getEigenvalue(0));
axis2.mult((float)pca.getEigenvalue(1));
}
image(opencv.image(), 0, opencv.image().height, opencv.image().width*3, opencv.image().height*3);
stroke(200);
pushMatrix();
translate(0, imgHeight);
scale(3, 3);
translate(centroid.x, centroid.y);
stroke(0, 255, 0);
line(0, 0, axis1.x, axis1.y);
stroke(255, 0, 0);
line(0, 0, axis2.x, axis2.y);
popMatrix();
fill(0, 255, 0);
text("PCA Object Axes:\nFirst two principle components centered at blob centroid", 10, height - 20);
}
}
void keyPressed() {
opencv.remember();
}
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