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143 lines
5.3 KiB
Markdown
143 lines
5.3 KiB
Markdown
---
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filename: learnopencv.py
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contributors:
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- ["Yogesh Ojha", "http://github.com/yogeshojha"]
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translators:
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- ["GengchenXU", "https://github.com/GengchenXU"]
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---
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OpenCV（开源计算机视觉）是一个编程功能库，主要面向实时计算机视觉。最初由英特尔开发，后来由Willow Garage，然后Itseez（后来被英特尔收购）支持。OpenCV 目前支持多种语言，如C++、Python、Java 等
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#### 安装
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有关在计算机上安装 OpenCV，请参阅这些文章。
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* [Windows 安装说明](https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_setup/py_setup_in_windows/py_setup_in_windows.html#install-opencv-python-in-windows)
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* [Mac 安装说明](https://medium.com/@nuwanprabhath/installing-opencv-in-macos-high-sierra-for-python-3-89c79f0a246a) (High Sierra)
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* [Linux 安装说明](https://www.pyimagesearch.com/2018/05/28/ubuntu-18-04-how-to-install-opencv) （Ubuntu 18.04)
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### 在这里，我们将专注于 OpenCV 的 Python 实现
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```python
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# OpenCV读取图片
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import cv2
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img = cv2.imread('cat.jpg')
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# 显示图片
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# imshow() 函数被用来显示图片
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cv2.imshow('Image', img)
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# 第一个参数是窗口的标题，第二个参数是image
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# 如果你得到错误，对象类型为None，你的图像路径可能是错误的。请重新检查图像包
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cv2.waitKey(0)
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# waitKey() 是一个键盘绑定函数，参数以毫秒为单位。对于GUI事件，必须使用waitKey()函数。
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# 保存图片
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cv2.imwrite('catgray.png', img)
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# 第一个参数是文件名，第二个参数是图像
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# 转换图像灰度
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gray_image = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
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# 从摄像头捕捉视频
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cap = cv2.VideoCapture(0)
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# 0 是你的相机，如果你有多台相机，你需要输入他们的id
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while True:
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# 一帧一帧地获取
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_, frame = cap.read()
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cv2.imshow('Frame', frame)
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# 当用户按下q ->退出
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if cv2.waitKey(1) & 0xFF == ord('q'):
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break
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# 相机必须释放
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cap.release()
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# 在文件中播放视频
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cap = cv2.VideoCapture('movie.mp4')
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while cap.isOpened():
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_, frame = cap.read()
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# 灰度播放视频
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gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
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cv2.imshow('frame', gray)
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if cv2.waitKey(1) & 0xFF == ord('q'):
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break
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cap.release()
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# 在OpenCV中画线
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# cv2.line(img, (x,y), (x1,y1), (color->r,g,b->0 to 255), thickness)(注 color颜色rgb参数 thickness粗细)
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cv2.line(img, (0, 0), (511, 511), (255, 0, 0), 5)
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# 画矩形
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# cv2.rectangle(img, (x,y), (x1,y1), (color->r,g,b->0 to 255), thickness)
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# 粗细= -1用于填充矩形
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cv2.rectangle(img, (384, 0), (510, 128), (0, 255, 0), 3)
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# 画圆
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# cv2.circle(img, (xCenter,yCenter), radius, (color->r,g,b->0 to 255), thickness)
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cv2.circle(img, (200, 90), 100, (0, 0, 255), -1)
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# 画椭圆
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cv2.ellipse(img, (256, 256), (100, 50), 0, 0, 180, 255, -1)
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# 在图像上增加文字
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cv2.putText(img, "Hello World!!!", (x, y), cv2.FONT_HERSHEY_SIMPLEX, 2, 255)
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# 合成图像
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img1 = cv2.imread('cat.png')
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img2 = cv2.imread('openCV.jpg')
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dst = cv2.addWeighted(img1, 0.5, img2, 0.5, 0)
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# 阈值图像
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# 二进制阈值
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_, thresImg = cv2.threshold(img, 127, 255, cv2.THRESH_BINARY)
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# Adaptive Thresholding
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adapThres = cv2.adaptiveThreshold(img, 255, cv2.ADAPTIVE_THRESH_GAUSSIAN_C, cv2.THRESH_BINARY, 11, 2)
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# 模糊的形象
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# 高斯模糊
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blur = cv2.GaussianBlur(img, (5, 5), 0)
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# 模糊中值
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medianBlur = cv2.medianBlur(img, 5)
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# Canny 边缘检测
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img = cv2.imread('cat.jpg', 0)
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edges = cv2.Canny(img, 100, 200)
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# 用Haar Cascades进行人脸检测
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# 下载 Haar Cascades 在 https://github.com/opencv/opencv/blob/master/data/haarcascades/
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import cv2
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import numpy as np
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face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
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eye_cascade = cv2.CascadeClassifier('haarcascade_eye.xml')
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img = cv2.imread('human.jpg')
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gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
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aces = face_cascade.detectMultiScale(gray, 1.3, 5)
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for x, y, w, h in faces:
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cv2.rectangle(img, (x, y), (x + w, y + h), (255, 0, 0), 2)
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roi_gray = gray[y : y + h, x : x + w]
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roi_color = img[y : y + h, x : x + w]
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eyes = eye_cascade.detectMultiScale(roi_gray)
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for ex, ey, ew, eh in eyes:
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cv2.rectangle(roi_color, (ex, ey), (ex + ew, ey + eh), (0, 255, 0), 2)
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cv2.imshow('img', img)
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cv2.waitKey(0)
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cv2.destroyAllWindows()
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# destroyAllWindows() destroys all windows.
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# 如果您希望销毁特定窗口，请传递您创建的窗口的确切名称。
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```
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### 进一步阅读：
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* Download Cascade from [https://github.com/opencv/opencv/blob/master/data/haarcascades](https://github.com/opencv/opencv/blob/master/data/haarcascades)
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* OpenCV 绘图函数 [https://docs.opencv.org/2.4/modules/core/doc/drawing_functions.html](https://docs.opencv.org/2.4/modules/core/doc/drawing_functions.html)
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* 最新的语言参考 [https://opencv.org](https://opencv.org)
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* 更多的资源 [https://en.wikipedia.org/wiki/OpenCV](https://en.wikipedia.org/wiki/OpenCV)
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* 优秀的的 OpenCV 教程
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* [https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_tutorials.html](https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_tutorials.html)
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* [https://realpython.com/python-opencv-color-spaces](https://realpython.com/python-opencv-color-spaces)
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* [https://pyimagesearch.com](https://pyimagesearch.com)
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* [https://www.learnopencv.com](https://www.learnopencv.com)
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