Notes on robotics, vision, and systems.
C and C++ provide the rand() and srand() functions for generating random numbers, and they can also be used when writing OpenCV code in C++. OpenCV also provides its own RNG class for generating random numbers, which is very convenient to use. This article mainly introduces how to use RNG and how to draw random lines based on the random numbers it generates.
This article introduces methods for drawing rectangles, circles, lines, and ellipses with C++ and OpenCV 4. It focuses on the definitions of OpenCV built-in functions (such as rectangle(), circle(), line(), and ellipse()) and the role of each parameter, and provides example programs for reference. It also summarizes methods for drawing polygons, including the polygon-border drawing function polylines(), the polygon-filling function fillPoly(), the function for drawing multiple polygons drawContours(), and more.
Replacing the background of a green-screen image involves ① color-space conversion, ② extracting the green-screen region, ③ inverting the green-screen region, and ④ copying the image. The various functions and code encountered along the way are also covered in detail in this article.
After splitting image channels, the output multi-channel sequence is typically stored using std::vector mv;, where mv[0], mv[1], and mv[2] correspond to the three BGR channels respectively. However, what is displayed now is essentially three single-channel images—in other words, three grayscale images. To restore intuitive color to the three images, you need to use the channel merging method described below.
OpenCV uses createTrackbar() to create a Trackbar. The function syntax and the purpose of each parameter are shown below.
Image pixel operations include read and write operations, arithmetic operations, logical operations, and more. Pixel operations are not only diverse; operations on grayscale images and color images also have their own characteristics. Operating on pixels allows us to access every pixel in an image and implement many unexpected functions.
Color space conversion function: cvtColor. GRAY: grayscale, with only one Channel for the grayscale value. BGR: the BGR color space, based on the three primary colors red, green, and blue (0~255), which are combined to form various colors. HSV: the hexagonal cone model, with Hue measured in degrees (0~180), Saturation in the range 0 ~ 255, and Value in the range 0 ~ 255.
First, download and extract OpenCV. I recommend downloading the Windows installer from the official OpenCV website. If the download is too slow, I have also uploaded the OpenCV4.5.2 installer to Aliyun Drive at https://www.aliyundrive.com/s/VGkaM7vyuck. Make sure to extract it to an English-only path.
The state machine is the most commonly used design model in engineering applications. With a state machine, we can easily implement decisions and branches in a program flowchart. A LabVIEW state machine consists of a While Loop, a Case Structure, and a shift register.
State machines are the most widely used design pattern in engineering applications. With a state machine, we can easily implement decisions and branches from program flowcharts. A LabVIEW state machine consists of a While loop, a case structure, and a shift register.
