This example shows how to draw different shapes on images.
First import an OpenCV function into Simulink® by using the OpenCV Code Import Wizard. The wizard creates a Simulink library that contains a subsystem and a C Caller block for the specified OpenCV function. The subsystem is then used in a preconfigured Simulink model. This subsystem accepts coordinates of a specified shape. A defined shape is then displayed on a Video Viewer.
You learn how to:
Import an OpenCV function into a Simulink library.
Use blocks from a generated library in a Simulink model.
Computer Vision Toolbox™ Interface for OpenCV in Simulink
Computer Vision Toolbox
To build the OpenCV libraries, identify a compatible C++ compiler for your operating
system, as described in Compiler Used to Build OpenCV Libraries. Configure the
identified compiler by using the
mex -setup c++ command. For more
information, see Choose a C++ Compiler.
These Simulink models are available in the
This example uses the
DrawFilledCircle.slx model. In this model,
subsystem_slwrap_drawFilledCircle subsystem resides in the
DrawCircle_Lib library. You create the
subsystem_slwrap_drawFilledCircle subsystem by using the
OpenCV Importer. The subsystem accepts the
y coordinates for the center of the circle and radius as input to
the subsystem. The subsystem creates a circle on an input image from the Image
From File block. The output is then displayed on a Video
To access the path to the example folder, at the MATLAB® command line, enter:
Before proceeding with these steps, ensure that you copy the example folder to a
writable folder location and change your current working folder to
...example\DrawShapes. All your output files are saved to this
To start the OpenCV Importer app, click Apps
on the MATLAB Toolstrip. The OpenCV import wizard opens to a Welcome page.
Specify the Project name as
Make sure that the project name does not contain any spaces. Click
In Specify OpenCV Library, specify these file locations, and then click Next.
Project root folder: Specify the path of your example folder. This path is the path to the writable project folder where you have saved your example files. All your output files are saved to this folder.
Source files: Specify the path of the
.cpp file located inside your project folder
Include files: Specify the path of the
.hpp header file located inside your project
Analyze your library to find the functions and types for import. Once the
analysis is complete, click Next. From the listed
functions, select the
drawFilledCircle function and click
From What to import, select the I/O Type for
InputOutput and other
In Create Simulink Library, verify the default values of OpenCV types. By default, Create a single C-caller block for the OpenCV function is selected to create a C Caller block with the subsystem. To create a Simulink library, click Next.
A Simulink library
DrawCircle_Lib is created from your
OpenCV code. You can use any of these blocks for model simulation. In this
example, the subsystem
To use the generated subsystem
with the Simulink model
In your MATLAB
Current Folder, right-click the model
DrawFilledCircle.slx and click
Open from the context menu. Drag the
generated subsystem to the model and connect the blocks.
Double-click the subsystem and verify the parameter values.
On the Simulink Toolstrip, in the Simulation tab,
click to simulate the model. After the simulation is
complete, the Video Viewer block displays the filled circle on the input
This example shows how to use a C Caller block in a Simulink model to draw an atom on an image.
OpenCV functions into Simulink by using the OpenCV Code Import
Wizard. During import, select the I/O Type for
shown in this graphic.
Once you import the functions, the
is created. This Simulink library contains subsystems and the C Caller blocks
required to draw an atom on an image.
Open the model
DrawAtomCcaller.slx. Drag the
slwrap_drawEllipse C Caller block from the Simulink
subsystem in the model. Create three copies of the C Caller block, and then
place these blocks at the four blank positions inside the
In the model, drag the
slwrap_drawFilledCircle C Caller
block from the Simulink library
DrawCircle_Lib and place the
block at the blank position.
On the Simulink Toolstrip, in the Simulation tab, click to simulate the model. After the simulation is complete, the Video Viewer block displays the atom on a white input image.