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)

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

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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