Unwarp an equirectangular projection into a perspective projection using openFrameworks.

CameraSphere.cpp

#include "ofMain.h"

class ofApp : public ofBaseApp {
public:
    ofImage img;
    ofEasyCam cam;
    ofSpherePrimitive sphere;
    float zoom = 0.5;
    float xoff = 0;
    float yoff = 0;
    
    void setup() {
        sphere.set(1000, 128);
        img.load("pano.jpg");
    }
    void update() {
        ofTextureData& tdata = img.getTexture().getTextureData();
        bool normalized = (tdata.textureTarget == GL_TEXTURE_RECTANGLE_ARB);
        float w = tdata.tex_t * (1/zoom);
        float h = tdata.tex_u * (1/zoom);
        if(w > 2 * h) {
            h = w / 2;
        } else {
            w = h * 2;
        }
        float x = (xoff * w + tdata.tex_t - w) / 2;
        float y = (yoff * h + tdata.tex_u - h) / 2;
        sphere.mapTexCoords(x, y, x+w, y+h);
    }
    void draw() {
        ofEnableDepthTest();
        cam.begin();
        img.getTexture().bind();
        sphere.draw();
        img.getTexture().unbind();
        cam.end();
    }
    void keyPressed(int key) {
        if(key == '=') {
            cam.setFov(cam.getFov() - 1);
        }
        if(key == '-') {
            cam.setFov(cam.getFov() + 1);
        }
        if(key == '[') {
            zoom *= .99;
        }
        if(key == ']') {
            zoom /= .99;
        }
        if(key == OF_KEY_LEFT) {
            xoff -= 0.01;
        }
        if(key == OF_KEY_RIGHT) {
            xoff += 0.01;
        }
        if(key == OF_KEY_UP) {
            yoff -= 0.01;
        }
        if(key == OF_KEY_DOWN) {
            yoff += 0.01;
        }
    }
};

int main() {
    ofSetupOpenGL(1280, 720, OF_WINDOW);
    ofRunApp(new ofApp());
}