使用python在open cv中使用鼠标事件绘制填充多边形

>单击鼠标左键,在单击的位置向多边形添加一个点
>单击鼠标右键完成数据输入,并使程序显示最终填充的多边形

我们需要几个变量来跟踪我们的进度：

>定义多边形的点列表.每个点都是一个元组(x,y)
>一个布尔标志,表示数据输入完成的时间
>作为奖励,鼠标光标的最后已知位置,因此我们可以为当前输入的片段(光标后面的一行)设置动画.

当发生适当的鼠标事件时,我们将使用鼠标回调定期更新这些变量：

> EVENT_MOUSEMOVE – 鼠标已移动,更新当前位置
> EVENT_LBUTTONDOWN – 用户按下鼠标左键,将当前位置添加到点列表中
> EVENT_RBUTTONDOWN – 用户按下鼠标右键,将数据输入标记为完成

最后,我们将有一个实现显示循环的函数.

此函数将首先创建一个命名窗口,绘制一个空白画布,并设置鼠标回调.然后它将通过以下方式反复更新屏幕：

>创建一个新的画布图像(在其上绘制)
>输入点时,使用cv2.polyline绘制连接的段
>使用cv2.line将当前段从最后输入的点指向当前位置,使用不同的颜色.
>显示新图像.
>等一段时间,在这样做时抽出窗口消息.

一旦数据输入过程完成,该函数将绘制最终填充的多边形和一个干净的画布图像,显示它,并在用户按下一个键时返回最终图像.

代码示例

import numpy as np
import cv2

# ============================================================================

CANVAS_SIZE = (600,800)

FINAL_LINE_COLOR = (255,255,255)
WORKING_LINE_COLOR = (127,127,127)

# ============================================================================

class PolygonDrawer(object):
    def __init__(self,window_name):
        self.window_name = window_name # Name for our window

        self.done = False # Flag signalling we're done
        self.current = (0,0) # Current position,so we can draw the line-in-progress
        self.points = [] # List of points defining our polygon


    def on_mouse(self,event,x,y,buttons,user_param):
        # Mouse callback that gets called for every mouse event (i.e. moving,clicking,etc.)

        if self.done: # Nothing more to do
            return

        if event == cv2.EVENT_MOUSEMOVE:
            # We want to be able to draw the line-in-progress,so update current mouse position
            self.current = (x,y)
        elif event == cv2.EVENT_LBUTTONDOWN:
            # Left click means adding a point at current position to the list of points
            print("Adding point #%d with position(%d,%d)" % (len(self.points),y))
            self.points.append((x,y))
        elif event == cv2.EVENT_RBUTTONDOWN:
            # Right click means we're done
            print("Completing polygon with %d points." % len(self.points))
            self.done = True


    def run(self):
        # Let's create our working window and set a mouse callback to handle events
        cv2.namedWindow(self.window_name,flags=cv2.CV_WINDOW_AUTOSIZE)
        cv2.imshow(self.window_name,np.zeros(CANVAS_SIZE,np.uint8))
        cv2.waitKey(1)
        cv2.cv.SetMouseCallback(self.window_name,self.on_mouse)

        while(not self.done):
            # This is our drawing loop,we just continuously draw new images
            # and show them in the named window
            canvas = np.zeros(CANVAS_SIZE,np.uint8)
            if (len(self.points) > 0):
                # Draw all the current polygon segments
                cv2.polylines(canvas,np.array([self.points]),False,FINAL_LINE_COLOR,1)
                # And  also show what the current segment would look like
                cv2.line(canvas,self.points[-1],self.current,WORKING_LINE_COLOR)
            # Update the window
            cv2.imshow(self.window_name,canvas)
            # And wait 50ms before next iteration (this will pump window messages meanwhile)
            if cv2.waitKey(50) == 27: # ESC hit
                self.done = True

        # User finised entering the polygon points,so let's make the final drawing
        canvas = np.zeros(CANVAS_SIZE,np.uint8)
        # of a filled polygon
        if (len(self.points) > 0):
            cv2.fillPoly(canvas,FINAL_LINE_COLOR)
        # And show it
        cv2.imshow(self.window_name,canvas)
        # Waiting for the user to press any key
        cv2.waitKey()

        cv2.destroyWindow(self.window_name)
        return canvas

# ============================================================================

if __name__ == "__main__":
    pd = PolygonDrawer("Polygon")
    image = pd.run()
    cv2.imwrite("polygon.png",image)
    print("Polygon = %s" % pd.points)

截图

在绘制过程中,我们输入了5个点,当前段显示为指向鼠标当前位置的较暗线：

绘图完成,程序显示整个多边形填充：

最终形象

控制台输出

Adding point #0 with position(257,144)
Adding point #1 with position(657,263)
Adding point #2 with position(519,478)
Adding point #3 with position(283,383)
Adding point #4 with position(399,126)
Adding point #5 with position(142,286)
Adding point #6 with position(165,38)
Completing polygon with 7 points.
Polygon = [(257,144),(657,263),(519,478),(283,383),(399,126),(142,286),(165,38)]