使用python在open cv中使用鼠标事件绘制填充多边形

Question

我试图在坐标之间绘制一个多边形,通过单击鼠标事件获得.

第一次单击应定义多边形的起始点.每次额外点击都应绘制上一次点击的线段.当整个点击点绘制多边形时,应填充多边形内部.

有人可以建议如何在我点击图像的点之间绘制多边形吗？我正在考虑cv2.polylines功能,但我不知道如何将其与SetMouseCallback功能集成.

Answer 1

为了使用户界面更直观(因为用户很难完全点击与起点相同的位置),让我们使用以下操作:

• 单击鼠标左键,在点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正在输入的片段(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,使用绘制连接的段 cv2.polyline
• 使用不同的颜色绘制从最后输入的点指向当前位置的当前段cv2.line.
• 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), x, 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, np.array([self.points]), 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)]