CV学习笔记(九):光流法的实现

import numpy as np
import cv2 as cv

cap = cv.VideoCapture("test.avi")
# params for ShiTomasi corner detection 设置 ShiTomasi 角点检测的参数
feature_params = dict(maxCorners=100,
                      qualityLevel=0.3,
                      minDistance=7,
                      blockSize=7)
# Parameters for lucas kanade optical flow 设置 lucas kanade 光流场的参数
# maxLevel 为使用的图像金字塔层数
lk_params = dict(winSize=(15, 15),
                 maxLevel=2,
                 criteria=(cv.TERM_CRITERIA_EPS | cv.TERM_CRITERIA_COUNT, 10, 0.03))
# Create some random colors 产生随机的颜色值
color = np.random.randint(0, 255, (100, 3))
# Take first frame and find corners in it 获取第一帧，并寻找其中的角点
(ret, old_frame) = cap.read()
old_gray = cv.cvtColor(old_frame, cv.COLOR_BGR2GRAY)
p0 = cv.goodFeaturesToTrack(old_gray, mask=None, **feature_params)
# Create a mask image for drawing purposes 创建一个掩膜为了后面绘制角点的光流轨迹
mask = np.zeros_like(old_frame)

# 视频文件输出参数设置
out_fps = 12.0  # 输出文件的帧率
fourcc = cv.VideoWriter_fourcc('M', 'P', '4', '2')
sizes = (int(cap.get(cv.CAP_PROP_FRAME_WIDTH)), int(cap.get(cv.CAP_PROP_FRAME_HEIGHT)))
out = cv.VideoWriter('E:/video/v5.avi', fourcc, out_fps, sizes)

while True:
    (ret, frame) = cap.read()
    frame_gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)
    # calculate optical flow 能够获取点的新位置
    p1, st, err = cv.calcOpticalFlowPyrLK(old_gray, frame_gray, p0, None, **lk_params)
    # Select good points 取好的角点，并筛选出旧的角点对应的新的角点
    good_new = p1[st == 1]
    good_old = p0[st == 1]
    # draw the tracks 绘制角点的轨迹
    for i, (new, old) in enumerate(zip(good_new, good_old)):
        a, b = new.ravel()
        c, d = old.ravel()
        mask = cv.line(mask, (a, b), (c, d), color[i].tolist(), 2)
        frame = cv.circle(frame, (a, b), 5, color[i].tolist(), -1)
    img = cv.add(frame, mask)
    cv.imshow('frame', img)
    out.write(img)
    k = cv.waitKey(200) & 0xff
    if k == 27:
        break
    # Now update the previous frame and previous points 更新当前帧和当前角点的位置
    old_gray = frame_gray.copy()
    p0 = good_new.reshape(-1, 1, 2)

out.release()
cv.destroyAllWindows()
cap.release()