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For anybody still looking for a solution, this is one way to achieve this using a depth camera as an example and you subscribe to both the color image topic and the camera_info topic:

#include <ros/ros.h>
#include <sensor_msgs/image_encodings.h>
#include <sensor_msgs/CameraInfo.h> 
#include <message_filters/subscriber.h>
#include <message_filters/time_synchronizer.h>

class ImageConverter
{
    ros::NodeHandle nh_;
    message_filters::Subscriber<sensor_msgs::Image> image_sub_;
    message_filters::Subscriber<sensor_msgs::CameraInfo> camera_info_sub_;
    typedef message_filters::TimeSynchronizer<sensor_msgs::Image, sensor_msgs::CameraInfo> approx_sync_policy;
    std::shared_ptr<approx_sync_policy> sync;

public:
ImageConverter(ros::NodeHandle &n)
:   nh_(n)
{
    image_sub_.subscribe(nh_, "/camera/color/image_raw", 1);
    camera_info_sub_.subscribe(nh_, "/camera/color/camera_info", 1);
    sync.reset(new approx_sync_policy(image_sub_, camera_info_sub_, 10));
    sync->registerCallback(std::bind(&ImageConverter::MultiSubscriberCB, this, std::placeholders::_1, std::placeholders::_2)); 
}

~ImageConverter() {}

private:
void MultiSubscriberCB(const sensor_msgs::ImageConstPtr& msg_image, const sensor_msgs::CameraInfoConstPtr& msg_camera_info) {
    ROS_INFO("inside callback");
}
};

int main(int argc, char** argv) {
    ros::init(argc, argv, "image_converter");
    ros::NodeHandle nh("~");
    ImageConverter ic(nh);

    ros::spin();
    return 0;
}