Pixel Perfect Collision

bool GameLayer::areSpritesColliding(cocos2d::CCSprite *spr1, cocos2d::CCSprite *spr2, bool pp) {
    bool isColliding = false;
    CCRect intersection;
    CCRect r1 = spr1->boundingBox();
    CCRect r2 = spr2->boundingBox();



    // Look for simple bounding box collision
    if (r1.intersectsRect(r2)) {
    // If we're not checking for pixel perfect collisions, return true
        if (!pp) {
            return true;
        }
        CCLog("Bounding Box Collision");

        float tempX;
        float tempY;
        float tempWidth;
        float tempHeight;

        if (r1.getMaxX() > r2.getMinX()) {
            tempX = r2.getMinX();
            tempWidth = r1.getMaxX() - r2.getMinX();
        } else {
            tempX = r1.getMinX();
            tempWidth = r2.getMaxX() - r1.getMinX();
        }

        if (r1.getMinY() < r2.getMaxY()) {
            tempY = r1.getMinY();
            tempHeight = r2.getMaxY() - r1.getMinY();
        } else {
            tempY = r2.getMinY();
            tempHeight = r1.getMaxY() - r2.getMinY();
        }

        intersection = CCRectMake(tempX * CC_CONTENT_SCALE_FACTOR(), tempY  * CC_CONTENT_SCALE_FACTOR(), tempWidth * CC_CONTENT_SCALE_FACTOR(), tempHeight * CC_CONTENT_SCALE_FACTOR());

        unsigned int x = intersection.origin.x;
        unsigned int y = intersection.origin.y;
        unsigned int w = intersection.size.width;
        unsigned int h = intersection.size.height;

        unsigned int numPixels = w * h;
        // Draw into the RenderTexture
        _rt->beginWithClear( 0, 0, 0, 0);

        // Render both sprites: first one in RED and second one in GREEN
        glColorMask(1, 0, 0, 1);
        spr1->visit();
        glColorMask(0, 1, 0, 1);
        spr2->visit();
        glColorMask(1, 1, 1, 1);

        // Get color values of intersection area
        ccColor4B *buffer = (ccColor4B *)malloc( sizeof(ccColor4B) * numPixels );
        glReadPixels(x, y, w, h, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

        _rt->end();

        // Read buffer
        unsigned int step = 1;
        for(unsigned int i=0; i<numPixels; i+=step) {
            ccColor4B color = buffer[i];
            //CCLog("Pixel color: %d, %d, %d", color.r, color.g, color.b);
            if (color.a > 0 && color.g > 0) {
                isColliding = true;
                CCLog("Colliding");
                break;
            }
        }

        // Free buffer memory
        free(buffer);
    }


    return isColliding;
}