如何在Python中使用OpenCV跟踪运动？

Question

我可以使用OpenCV在Python中从我的网络摄像头获取画面。虽然camshift的例子跟我想要的差不多，但我不想手动去定义物体。我想要的是在多个画面中，找出那些变化的像素的中心点，也就是移动物体的中心。

Answer 1

if faces:
    for ((x, y, w, h), n) in faces:
        pt1 = (int(x * image_scale), int(y * image_scale))
        pt2 = (int((x + w) * image_scale), int((y + h) * image_scale))
        ptcx=((pt1[0]+pt2[0])/2)/128
        ptcy=((pt1[1]+pt2[1])/2)/96
        cv.Rectangle(gray, pt1, pt2, cv.RGB(255, 0, 0), 3, 8, 0)
        print ptcx;
        print ptcy;
        b=('S'+str(ptcx)+str(ptcy));

这是我尝试获取移动物体中心位置的代码部分，使用的是一个矩形边界来进行跟踪。

Answer 2

可以查看这个论坛帖子 使用OpenCV进行运动追踪。

我相信你能看懂源代码，并把它翻译成 Python，对吧？

Answer 3

我有一些代码，它是从一篇博客文章中找到的C语言版本翻译过来的，这篇文章的标题是《使用OpenCV进行运动检测》。

#!/usr/bin/env python

import cv

class Target:

    def __init__(self):
        self.capture = cv.CaptureFromCAM(0)
        cv.NamedWindow("Target", 1)

    def run(self):
        # Capture first frame to get size
        frame = cv.QueryFrame(self.capture)
        frame_size = cv.GetSize(frame)
        color_image = cv.CreateImage(cv.GetSize(frame), 8, 3)
        grey_image = cv.CreateImage(cv.GetSize(frame), cv.IPL_DEPTH_8U, 1)
        moving_average = cv.CreateImage(cv.GetSize(frame), cv.IPL_DEPTH_32F, 3)

        first = True

        while True:
            closest_to_left = cv.GetSize(frame)[0]
            closest_to_right = cv.GetSize(frame)[1]

            color_image = cv.QueryFrame(self.capture)

            # Smooth to get rid of false positives
            cv.Smooth(color_image, color_image, cv.CV_GAUSSIAN, 3, 0)

            if first:
                difference = cv.CloneImage(color_image)
                temp = cv.CloneImage(color_image)
                cv.ConvertScale(color_image, moving_average, 1.0, 0.0)
                first = False
            else:
                cv.RunningAvg(color_image, moving_average, 0.020, None)

            # Convert the scale of the moving average.
            cv.ConvertScale(moving_average, temp, 1.0, 0.0)

            # Minus the current frame from the moving average.
            cv.AbsDiff(color_image, temp, difference)

            # Convert the image to grayscale.
            cv.CvtColor(difference, grey_image, cv.CV_RGB2GRAY)

            # Convert the image to black and white.
            cv.Threshold(grey_image, grey_image, 70, 255, cv.CV_THRESH_BINARY)

            # Dilate and erode to get people blobs
            cv.Dilate(grey_image, grey_image, None, 18)
            cv.Erode(grey_image, grey_image, None, 10)

            storage = cv.CreateMemStorage(0)
            contour = cv.FindContours(grey_image, storage, cv.CV_RETR_CCOMP, cv.CV_CHAIN_APPROX_SIMPLE)
            points = []

            while contour:
                bound_rect = cv.BoundingRect(list(contour))
                contour = contour.h_next()

                pt1 = (bound_rect[0], bound_rect[1])
                pt2 = (bound_rect[0] + bound_rect[2], bound_rect[1] + bound_rect[3])
                points.append(pt1)
                points.append(pt2)
                cv.Rectangle(color_image, pt1, pt2, cv.CV_RGB(255,0,0), 1)

            if len(points):
                center_point = reduce(lambda a, b: ((a[0] + b[0]) / 2, (a[1] + b[1]) / 2), points)
                cv.Circle(color_image, center_point, 40, cv.CV_RGB(255, 255, 255), 1)
                cv.Circle(color_image, center_point, 30, cv.CV_RGB(255, 100, 0), 1)
                cv.Circle(color_image, center_point, 20, cv.CV_RGB(255, 255, 255), 1)
                cv.Circle(color_image, center_point, 10, cv.CV_RGB(255, 100, 0), 1)

            cv.ShowImage("Target", color_image)

            # Listen for ESC key
            c = cv.WaitKey(7) % 0x100
            if c == 27:
                break

if __name__=="__main__":
    t = Target()
    t.run()