弧长与面积

image.png image.png image.png

def measure_function(image):
    dst = cv.GaussianBlur(image,(7,7),0)
    gray = cv.cvtColor(dst, cv.COLOR_BGR2GRAY)
    ret, binary = cv.threshold(gray, 0, 255, cv.THRESH_BINARY_INV | cv.THRESH_OTSU)
    print("二值阈值：%s" % ret)
    cv.imshow("Binary image", binary)
    outImage, contours, hireachy = cv.findContours(binary, cv.RETR_EXTERNAL, cv.CHAIN_APPROX_SIMPLE)
    for i, contour in enumerate(contours):
        area = cv.contourArea(contour)  # 面积
        x, y, w, h = cv.boundingRect(contour)  # 外接矩形
        rate = min(w,h)/max(w,h)
        print("宽高比：%s"%rate)
        mm = cv.moments(contour)  # 几何矩
        print(type(mm))
        cx = mm['m10']/mm['m00']
        cy = mm['m01']/mm['m00']
        cv.circle(image, (np.int(cx), np.int(cy)), 3, (0, 255, 255), -1)#中心
        cv.rectangle(image, (x, y), (x+w, y+h), (0, 0, 255), 2)
        print("面积：%s"%area)
    cv.imshow("measure-contours", image)

image.png

cv.approxPolyDP

def measure_function(image):
    dst = cv.GaussianBlur(image, (7, 7), 0)
    gray = cv.cvtColor(dst, cv.COLOR_BGR2GRAY)
    ret, binary = cv.threshold(
        gray, 0, 255, cv.THRESH_BINARY_INV | cv.THRESH_OTSU)
    print("二值阈值：%s" % ret)
    cv.imshow("Binary image", binary)
    outImage, contours, hireachy = cv.findContours(
        binary, cv.RETR_EXTERNAL, cv.CHAIN_APPROX_SIMPLE)
    for i, contour in enumerate(contours):
        x, y, w, h = cv.boundingRect(contour)  # 外接矩形
        mm = cv.moments(contour)  # 几何矩
        print(type(mm))
        cx = mm['m10']/mm['m00']
        cy = mm['m01']/mm['m00']
        cv.circle(image, (np.int(cx), np.int(cy)), 3, (0, 255, 255), -1)  # 中心

        '''
            cv.approxPolyDP：
                curve：contour
                epsilon = 4 ：越小越逼近真实形状
                closed = True
        '''
        approxCurve = cv.approxPolyDP(contour, 4, closed=True)
        print(approxCurve.shape)
        if approxCurve.shape[0] > 6:  # 边数大于6，近似圆形，椭圆
            cv.drawContours(image, contours, i, (0, 255, 0), 2)
        if approxCurve.shape[0] == 3:  # 三角形
            cv.drawContours(image, contours, i, (0, 0, 255), 2)
        if approxCurve.shape[0] == 4:  # 四角形
            cv.drawContours(image, contours, i, (0, 255, 125), 2)
    cv.imshow("measure-contours", image)

image.png