如何使用opencv在图像上动态画一条线？ [提供的代码，无法找出错误]

Posted 2023-03-16

【中文标题】如何使用opencv在图像上动态画一条线？ [提供的代码，无法找出错误]

【英文标题】：How to dynamically draw a line on image using opencv? [code provided, can't figure out error]

【发布时间】：2021-05-18 03:10:34

【问题描述】：

为了尝试在图像上动态绘制，我编写了这个脚本。

点击鼠标左键时应该开始行。 （单击左键）鼠标拖动时，坐标应实时保存，从而绘制一条线

以下是我写的代码：

import numpy as np
import cv2
from absl import app, flags
import imutils



FLAGS = flags.FLAGS

flags.DEFINE_string('img', './image.jpg',
                'PATH TO THE IMAGE ON WHICH LINES NEED TO BE DRAWN')



#%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


def main(argv):


  def draw_line(event, x, y, flags, param):
    global ix, iy, DRAW, xx, yy
    # DRAW = False

    if event == cv2.EVENT_LBUTTONDOWN:

        DRAW = True
        # save the coordinates of start
        ix , iy = x , y
        print(f"CLICKED AT X->ix,Y->iy")

    elif event == cv2.EVENT_MOUSEMOVE:
        #if DRAW != None:
            if DRAW == True:

                # if mouse moves, previous coodinates have been saved in ix, iy
                # new dynamic coordinates will be in x,y
                print(f"LINE : X->ix,Y->iy---------------->X->x,Y->y")
                cv2.line(img, (ix, iy), (x, y), color=(0,0,255),thickness= 15, lineType=cv2.LINE_AA )
                xx = x
                yy = y
    elif event == cv2.EVENT_LBUTTONUP:
        # discard the previous coordinates
        DRAW = False
        print(f"PTS were : ix,iy--->xx,yy")



  img = cv2.imread(FLAGS.img)
  img = imutils.resize(img, width=1500)
  cv2.namedWindow('image')
  cv2.setMouseCallback('image', draw_line)
  while True:
     cv2.imshow('image', img)
     k = cv2.waitKey(0) & 0xFF
     if k ==ord('q'):
         break
         cv2.destroyAllWindows()




if __name__=='__main__':
   app.run(main)

点打印正确，但我没有看到任何线条。有人可以找出错误吗？

【参考方案1】：

问题似乎出在waitkey上。

您正在反复调用 cv2.imshow，但是

cv2.waitKey(0) 查找将更新图像的按键。所以你无限期地等待

waitKey(1) 将每 1 毫秒更新一次图像