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Python+OpenCV实现在图像上绘制矩形

发布于：2022-03-22 09:36:15  栏目：技术文档

话不多说，直接上代码`import copyimport cv2import numpy as np

WIN_NAME = ‘draw_rect’

class Rect(object): def init(self): self.tl = (0, 0) self.br = (0, 0)

  1. def regularize(self):
  2.     """
  3.     make sure tl = TopLeft point, br = BottomRight point
  4.     """
  5.     pt1 = (min(self.tl[0], self.br[0]), min(self.tl[1], self.br[1]))
  6.     pt2 = (max(self.tl[0], self.br[0]), max(self.tl[1], self.br[1]))
  7.     self.tl = pt1
  8.     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

  1. @staticmethod
  2. def __clip(value, low, high):
  3.     """
  4.     clip value between low and high
  5.     Parameters
  6.     ----------
  7.     value: a number
  8.         value to be clipped
  9.     low: a number
  10.         low limit
  11.     high: a number
  12.         high limit
  13.     Returns
  14.     -------
  15.     output: a number
  16.         clipped value
  17.     """
  18.     output = max(value, low)
  19.     output = min(output, high)
  20.     return output
  22. def shrink_point(self, x, y):
  23.     """
  24.     shrink point (x, y) to inside image_for_show
  25.     Parameters
  26.     ----------
  27.     x, y: int, int
  28.         coordinate of a point
  29.     Returns
  30.     -------
  31.     x_shrink, y_shrink: int, int
  32.         shrinked coordinate
  33.     """
  34.     height, width = self.image_for_show.shape[0:2]
  35.     x_shrink = self.__clip(x, 0, width)
  36.     y_shrink = self.__clip(y, 0, height)
  37.     return (x_shrink, y_shrink)
  39. def append(self):
  40.     """
  41.     add a rect to rects list
  42.     """
  43.     self.rects.append(copy.deepcopy(self.current_rect))
  45. def pop(self):
  46.     """
  47.     pop a rect from rects list
  48.     """
  49.     rect = Rect()
  50.     if self.rects:
  51.         rect = self.rects.pop()
  52.     return rect
  54. def reset_image(self):
  55.     """
  56.     reset image_for_show using original image
  57.     """
  58.     self.image_for_show = self.original_image.copy()
  60. def draw(self):
  61.     """
  62.     draw rects on image_for_show
  63.     """
  64.     for rect in self.rects:
  65.         cv2.rectangle(self.image_for_show, rect.tl, rect.br,
  66.                       color=self.color, thickness=self.thickness)
  68. def draw_current_rect(self):
  69.     """
  70.     draw current rect on image_for_show
  71.     """
  72.     cv2.rectangle(self.image_for_show,
  73.                   self.current_rect.tl, self.current_rect.br,
  74.                   color=self.color, thickness=self.thickness)

def onmouse_draw_rect(event, x, y, flags, draw_rects): if event == cv2.EVENT_LBUTTONDOWN:

  1.     # pick first point of rect
  2.     print('pt1: x = %d, y = %d' % (x, y))
  3.     draw_rects.left_button_down = True
  4.     draw_rects.current_rect.tl = (x, y)
  5. if draw_rects.left_button_down and event == cv2.EVENT_MOUSEMOVE:
  6.     # pick second point of rect and draw current rect
  7.     draw_rects.current_rect.br = draw_rects.shrink_point(x, y)
  8.     draw_rects.reset_image()
  9.     draw_rects.draw()
  10.     draw_rects.draw_current_rect()
  11. if event == cv2.EVENT_LBUTTONUP:
  12.     # finish drawing current rect and append it to rects list
  13.     draw_rects.left_button_down = False
  14.     draw_rects.current_rect.br = draw_rects.shrink_point(x, y)
  15.     print('pt2: x = %d, y = %d' % (draw_rects.current_rect.br[0],
  16.                                    draw_rects.current_rect.br[1]))
  17.     draw_rects.current_rect.regularize()
  18.     draw_rects.append()
  19. if (not draw_rects.left_button_down) and event == cv2.EVENT_RBUTTONDOWN:
  20.     # pop the last rect in rects list
  21.     draw_rects.pop()
  22.     draw_rects.reset_image()
  23.     draw_rects.draw()

if name == ‘main‘:

  1. #image = np.zeros((256, 256, 3), np.uint8)
  2. image = cv2.imread("111.jpg")
  3. draw_rects = DrawRects(image, (0, 255, 0), 2)
  4. cv2.namedWindow(WIN_NAME, 0)
  5. cv2.setMouseCallback(WIN_NAME, onmouse_draw_rect, draw_rects)
  6. while True:
  7.     cv2.imshow(WIN_NAME, draw_rects.image_for_show)
  8.     key = cv2.waitKey(30)
  9.     if key == 27:  # ESC
  10.         break
  11. 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

Python客栈送红包、纸质书

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：以上就是Python+OpenCV实现在图像上绘制矩形的详细内容

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