Python+OpenCV如何实现在图像上绘制矩形

小编给大家分享一下Python+OpenCV如何实现在图像上绘制矩形，希望大家阅读完这篇文章之后都有所收获，下面让我们一起去探讨吧！

代码

import copyimport cv2import numpy as np WIN_NAME = 'draw_rect'  class Rect(object):    def __init__(self):        self.tl = (0, 0)        self.br = (0, 0)     def regularize(self):        """        make sure tl = TopLeft point, br = BottomRight point        """        pt1 = (min(self.tl[0], self.br[0]), min(self.tl[1], self.br[1]))        pt2 = (max(self.tl[0], self.br[0]), max(self.tl[1], self.br[1]))        self.tl = pt1        self.br = pt2  class DrawRects(object):    def __init__(self, image, color, thickness=1):        self.original_image = image        self.image_for_show = image.copy()        self.color = color        self.thickness = thickness        self.rects = []        self.current_rect = Rect()        self.left_button_down = False     @staticmethod    def __clip(value, low, high):        """        clip value between low and high        Parameters        ----------        value: a number            value to be clipped        low: a number            low limit        high: a number            high limit        Returns        -------        output: a number            clipped value        """        output = max(value, low)        output = min(output, high)        return output     def shrink_point(self, x, y):        """        shrink point (x, y) to inside image_for_show        Parameters        ----------        x, y: int, int            coordinate of a point        Returns        -------        x_shrink, y_shrink: int, int            shrinked coordinate        """        height, width = self.image_for_show.shape[0:2]        x_shrink = self.__clip(x, 0, width)        y_shrink = self.__clip(y, 0, height)        return (x_shrink, y_shrink)     def append(self):        """        add a rect to rects list        """        self.rects.append(copy.deepcopy(self.current_rect))     def pop(self):        """        pop a rect from rects list        """        rect = Rect()        if self.rects:            rect = self.rects.pop()        return rect     def reset_image(self):        """        reset image_for_show using original image        """        self.image_for_show = self.original_image.copy()     def draw(self):        """        draw rects on image_for_show        """        for rect in self.rects:            cv2.rectangle(self.image_for_show, rect.tl, rect.br,                          color=self.color, thickness=self.thickness)     def draw_current_rect(self):        """        draw current rect on image_for_show        """        cv2.rectangle(self.image_for_show,                      self.current_rect.tl, self.current_rect.br,                      color=self.color, thickness=self.thickness)  def onmouse_draw_rect(event, x, y, flags, draw_rects):    if event == cv2.EVENT_LBUTTONDOWN:        # pick first point of rect        print('pt1: x = %d, y = %d' % (x, y))        draw_rects.left_button_down = True        draw_rects.current_rect.tl = (x, y)    if draw_rects.left_button_down and event == cv2.EVENT_MOUSEMOVE:        # pick second point of rect and draw current rect        draw_rects.current_rect.br = draw_rects.shrink_point(x, y)        draw_rects.reset_image()        draw_rects.draw()        draw_rects.draw_current_rect()    if event == cv2.EVENT_LBUTTONUP:        # finish drawing current rect and append it to rects list        draw_rects.left_button_down = False        draw_rects.current_rect.br = draw_rects.shrink_point(x, y)        print('pt2: x = %d, y = %d' % (draw_rects.current_rect.br[0],                                       draw_rects.current_rect.br[1]))        draw_rects.current_rect.regularize()        draw_rects.append()    if (not draw_rects.left_button_down) and event == cv2.EVENT_RBUTTONDOWN:        # pop the last rect in rects list        draw_rects.pop()        draw_rects.reset_image()        draw_rects.draw()  if __name__ == '__main__':    #image = np.zeros((256, 256, 3), np.uint8)    image = cv2.imread("111.jpg")    draw_rects = DrawRects(image, (0, 255, 0), 2)    cv2.namedWindow(WIN_NAME, 0)    cv2.setMouseCallback(WIN_NAME, onmouse_draw_rect, draw_rects)    while True:        cv2.imshow(WIN_NAME, draw_rects.image_for_show)        key = cv2.waitKey(30)        if key == 27:  # ESC            break    cv2.destroyAllWindows()

运行效果

补充

当然Python+OpenCV不仅能做到在图像上绘制任意大小矩形，还能实现鼠标点击图像时会显示其坐标值

下面是实现代码

import cv2import numpy as np img = cv2.imread("111.jpg")  # print img.shape def on_EVENT_LBUTTONDOWN(event, x, y, flags, param):    if event == cv2.EVENT_LBUTTONDOWN:        xy = "%d,%d" % (x, y)        print        xy        cv2.circle(img, (x, y), 1, (255, 0, 0), thickness=-1)        cv2.putText(img, xy, (x, y), cv2.FONT_HERSHEY_PLAIN,                    1.0, (255, 255, 255), thickness=1)        cv2.imshow("image", img)  cv2.namedWindow("image",cv2.WINDOW_KEEPRATIO)cv2.setMouseCallback("image", on_EVENT_LBUTTONDOWN)cv2.imshow("image", img) while (True):    try:        cv2.waitKey(100)    except Exception:        cv2.destroyWindow("image")        break cv2.waitKey(0)cv2.destroyAllWindow()

运行结果：

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