OpenGL Simple GLSL Shader ROS Package

This is a ROS package for providing simple implementation to utilize OpenGL shader (GLSL) code with a GPU-powered machine under ROS environment. The repository includes a simple class that retrieves OpenCV image as a texture, processes it with GLSL shader codes, and writes the result back to another OpenCV image.

How to build?

Setup ROS

See http://wiki.ros.org/Installation and also setup catkin tools with the command below.

sudo apt install catkin-tools

Setup catkin workspace

mkdir -P ~/catkin/src
cd ~/catkin
catkin init

Clone this repository

cd ~/catkin/src
git clone <repository_path>

Install prerequisite packages

Install usb_cam node for example applications.

sudo apt-get install ros-kinetic-usb-cam

Build

catkin build

Run example nodes

This repository includes example nodes that extract pixels with a specific color. The algorithms of color conversion and extraction are implemented in GLSL shader code.

roslaunch opengl_ros color_extraction_gpu.launch

You can also launch a CPU implementation version for performance comparison with the following command.

roslaunch opengl_ros color_extraction_cpu.launch

We have perfomed simple comparison of the performance of two nodes on Intel Core i5 5300U 2.3GHz (HD Graphics 5500). Execution time of GPU includes texture transmission between CPU and GPU.

Resolution	CPU	GPU
320x240	5.85 ms	1.25 ms
640x480	21.8 ms	4.30 ms
1280x720	60.0 ms	12.3 ms

A simple instruction for OpenGL renderer class

cgs::SimpleRenderer class in opengl_ros_lib package wraps everything for ease of use. You can just instantiate the class,

cgs::SimpleRenderer renderer(
    width, height, 
    vertexShader, fragmentShader
);

and call render method to perform rendering on an OpenCV image. vertexShader and fragmentShader arguments can take your own custom shaders.

//Get pointer of the image in the message.
auto cv_ptr = cv_bridge::toCvShare(msg, sensor_msgs::image_encodings::BGR8);

//Feed the image to the shader and render on the output image.
cv::Mat output(height, width, CV_8UC3);
renderer_->render(output_, cv_ptr->image);

Please look inside simple_renderer_nodecore.cpp for the reference of usage.