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2024-12-23 09:41:36 +00:00 · 2020-05-19 16:43:49 +08:00 · 2020-05-19 16:43:49 +08:00 · 2877c63f00
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+---
+category: tool
+tool: OpenCV
+filename: learnopencv.py
+contributors:
+    - ["Yogesh Ojha", "http://github.com/yogeshojha"]
+translators:
+    - ["GengchenXU", "https://github.com/GengchenXU"]
+lang: zh-cn
+---
+### Opencv
+
+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
+
+#### 安装
+有关在计算机上安装 OpenCV，请参阅这些文章。
+
+* 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]()
+* Mac 安装说明 (High Sierra): [https://medium.com/@nuwanprabhath/installing-opencv-in-macos-high-sierra-for-python-3-89c79f0a246a]()
+* Linux 安装说明 （Ubuntu 18.04): [https://www.pyimagesearch.com/2018/05/28/ubuntu-18-04-how-to-install-opencv]()
+
+### 在这里，我们将专注于 OpenCV 的 python 实现
+
+```python
+# OpenCV读取图片
+import cv2
+img = cv2.imread('cat.jpg')
+
+# 显示图片
+# imshow() 函数被用来显示图片
+cv2.imshow('Image',img)
+# 第一个参数是窗口的标题，第二个参数是image
+# 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
+cv2.waitKey(0)
+# 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。
+
+# Writing an image
+cv2.imwrite('catgray.png',img)
+# 第一个参数是文件名，第二个参数是图像
+
+# 转换图像灰度
+gray_image = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
+
+# 从摄像头捕捉视频
+cap = cv2.VideoCapture(0)
+#0 是你的相机，如果你有多台相机，你需要输入他们的id
+while(True):
+    # 一帧一帧地获取
+    _, frame = cap.read()
+    cv2.imshow('Frame',frame)
+    # 当用户按下q ->退出
+    if cv2.waitKey(1) & 0xFF == ord('q'):
+        break
+# 相机必须释放
+cap.release()
+
+# 在文件中播放视频
+cap = cv2.VideoCapture('movie.mp4')
+while(cap.isOpened()):
+    _, frame = cap.read()
+    # 灰度播放视频
+    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
+    cv2.imshow('frame',gray)
+    if cv2.waitKey(1) & 0xFF == ord('q'):
+        break
+cap.release()
+
+# 在OpenCV中画线
+# 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)
+cv2.line(img,(0,0),(511,511),(255,0,0),5)
+
+# 画矩形
+# cv2.rectangle(img,(x,y),(x1,y1),(color->r,g,b->0 to 255),thickness)
+# 粗细= -1用于填充矩形
+cv2.rectangle(img,(384,0),(510,128),(0,255,0),3)
+
+# 画圆
+cv2.circle(img,(xCenter,yCenter), radius, (color->r,g,b->0 to 255), thickness)
+cv2.circle(img,(200,90), 100, (0,0,255), -1)
+
+# 画椭圆
+cv2.ellipse(img,(256,256),(100,50),0,0,180,255,-1)
+
+# 在图像上增加文字
+cv2.putText(img,"Hello World!!!", (x,y), cv2.FONT_HERSHEY_SIMPLEX, 2, 255)
+
+# 合成图像
+img1 = cv2.imread('cat.png')
+img2 = cv2.imread('openCV.jpg')
+dst = cv2.addWeighted(img1,0.5,img2,0.5,0)
+
+# 阈值图像
+# 二进制阈值
+_,thresImg = cv2.threshold(img,127,255,cv2.THRESH_BINARY)
+# Adaptive Thresholding
+adapThres = cv2.adaptiveThreshold(img,255,cv2.ADAPTIVE_THRESH_GAUSSIAN_C, cv2.THRESH_BINARY,11,2)
+
+# 模糊的形象
+# 高斯模糊
+blur = cv2.GaussianBlur(img,(5,5),0)
+# 模糊中值
+medianBlur = cv2.medianBlur(img,5)
+
+# Canny 边缘检测
+img = cv2.imread('cat.jpg',0)
+edges = cv2.Canny(img,100,200)
+
+# 用Haar Cascades进行人脸检测
+# 下载 Haar Cascades 在 https://github.com/opencv/opencv/blob/master/data/haarcascades/
+import cv2
+import numpy as np
+face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
+eye_cascade = cv2.CascadeClassifier('haarcascade_eye.xml')
+
+img = cv2.imread('human.jpg')
+gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
+
+aces = face_cascade.detectMultiScale(gray, 1.3, 5)
+for (x,y,w,h) in faces:
+    cv2.rectangle(img,(x,y),(x+w,y+h),(255,0,0),2)
+    roi_gray = gray[y:y+h, x:x+w]
+    roi_color = img[y:y+h, x:x+w]
+    eyes = eye_cascade.detectMultiScale(roi_gray)
+    for (ex,ey,ew,eh) in eyes:
+        cv2.rectangle(roi_color,(ex,ey),(ex+ew,ey+eh),(0,255,0),2)
+
+cv2.imshow('img',img)
+cv2.waitKey(0)
+
+cv2.destroyAllWindows()
+# destroyAllWindows() destroys all windows. 
+# 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。
+```
+
+### 进一步阅读：
+
+* Download Cascade from [https://github.com/opencv/opencv/blob/master/data/haarcascades]()
+* OpenCV 绘图函数 [https://docs.opencv.org/2.4/modules/core/doc/drawing_functions.html]()
+* 最新的语言参考 [https://opencv.org]()
+* 更多的资源 [https://en.wikipedia.org/wiki/OpenCV]()
+* 优秀的的 OpenCV 教程
+    * [https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_tutorials.html]()
+    * [https://realpython.com/python-opencv-color-spaces]()
+    * [https://pyimagesearch.com]()
+    * [https://www.learnopencv.com]()