package com.chameleonvision.vision.camera;

import org.apache.commons.math3.fraction.Fraction;
import org.apache.commons.math3.util.FastMath;

public class CameraStaticProperties {

    public final int imageWidth;
    public final int imageHeight;
    public final double fov;
    public final double imageArea;
    public final double centerX;
    public final double centerY;
    public final double horizontalFocalLength;
    public final double verticalFocalLength;

    public CameraStaticProperties(int imageWidth, int imageHeight, double fov) {
        this.imageWidth = imageWidth;
        this.imageHeight = imageHeight;
        this.fov = fov;
        imageArea = this.imageWidth * this.imageHeight;
        centerX = ((double) this.imageWidth / 2) - 0.5;
        centerY = ((double) this.imageHeight / 2) - 0.5;

        // pinhole model calculations
        double diagonalView = FastMath.toRadians(this.fov);
        Fraction aspectFraction = new Fraction(this.imageWidth, this.imageHeight);
        int horizontalRatio = aspectFraction.getNumerator();
        int verticalRatio = aspectFraction.getDenominator();
        double diagonalAspect = FastMath.hypot(horizontalRatio, verticalRatio);
        double horizontalView = FastMath.atan(FastMath.tan(diagonalView / 2) * (horizontalRatio / diagonalAspect)) * 2;
        double verticalView = FastMath.atan(FastMath.tan(diagonalView / 2) * (verticalRatio / diagonalAspect)) * 2;
        horizontalFocalLength = this.imageWidth / (2 * FastMath.tan(horizontalView /2));
        verticalFocalLength = this.imageHeight / (2 * FastMath.tan(verticalView /2));
    }
}