python 中使用opencv_python使用opencv

参考：
https://blog.csdn.net/liuqinshouss/article/details/78696032
https://blog.csdn.net/dcrmg/article/details/78147219
https://blog.csdn.net/hjxu2016/article/details/77833336/
https://blog.csdn.net/lanyuelvyun/article/details/76614872

1.文件中文的问题

## 读取图像，解决imread不能读取中文路径的问题
def cv_imread(filePath):
    cv_img=cv2.imdecode(np.fromfile(filePath,dtype=np.uint8),-1)
    ## imdecode读取的是rgb，如果后续需要opencv处理的话，需要转换成bgr，转换后图片颜色会变化
    ##cv_img=cv2.cvtColor(cv_img,cv2.COLOR_RGB2BGR)
    return cv_img

##保存Mat， imgMat为要保存的图像， savedFile为文件的路径字符串
cv2.imencode('.jpg', imgMat)[1].tofile(savedFile)
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2.pil image与opencv mat转换的问题
image转opencv mat

import cv2
from PIL import Image
import numpy
 
image = Image.open("plane.jpg")
image.show()
img = cv2.cvtColor(numpy.asarray(image),cv2.COLOR_RGB2BGR)

# 假如是单通道的话
#img = numpy.asarray(binaryImg)

cv2.imshow("OpenCV",img)
cv2.waitKey()
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opencv mat 转image

import cv2
from PIL import Image
import numpy
 
img = cv2.imread("plane.jpg")
cv2.imshow("OpenCV",img)
image = Image.fromarray(cv2.cvtColor(img,cv2.COLOR_BGR2RGB))
image.show()
cv2.waitKey()
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3.findcontours

import cv2  
 
img = cv2.imread("./test.jpg")  
 
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)  
ret, binary = cv2.threshold(gray,127,255,cv2.THRESH_BINARY)  
 
contours, hierarchy = cv2.findContours(binary,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)  
cv2.drawContours(img,contours,-1,(0,0,255),3)  
 
cv2.imshow("img", img)  
cv2.waitKey(0)  
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4.绘制通过minAreaRect获得的rotatedRect

rRect = cv2.minAreaRect(contours[0])
box = cv2.boxPoints(rRect)
# cnt = np.array([[x1,y1],[x2,y2],[x3,y3],[x4,y4]]) # 必须是array数组的形式
# rect = cv2.minAreaRect(cnt) # 得到最小外接矩形的（中心(x,y), (宽,高), 旋转角度）
# box = cv2.cv.BoxPoints(rect) # 获取最小外接矩形的4个顶点坐标(ps: cv2.boxPoints(rect) for OpenCV 3.x)
box = np.int0(box)
# 画出来
cv2.drawContours(img, [box], 0, (255, 0, 0), 1)
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