python opencv鼠标画矩形框之cv2.rectangle()函数
目录
- cv2.rectangle()函数说明
- 参数说明
- 利用鼠标回调函数交互式画矩形框
- 总结
关于鼠标回调函数的说明可以参考：opencv-python的鼠标交互操作
cv2.rectangle()函数说明
参数说明
导入cv2后，通过help(cv2.rectangle)可以看到函数的帮助文档如下：
rectangle(...)
rectangle(img, pt1, pt2, color[, thickness[, lineType[, shift]]]) -> img
. @brief Draws a simple, thick, or filled up-right rectangle.
.
. The function cv::rectangle draws a rectangle outline or a filled rectangle whose two opposite corners
. are pt1 and pt2.
.
. @param img Image.
. @param pt1 Vertex of the rectangle.
. @param pt2 Vertex of the rectangle opposite to pt1 .
. @param color Rectangle color or brightness (grayscale image).
. @param thickness Thickness of lines that make up the rectangle. Negative values, like #FILLED,
. mean that the function has to draw a filled rectangle.
. @param lineType Type of the line. See #LineTypes
. @param shift Number of fractional bits in the point coordinates.
rectangle(img, rec, color[, thickness[, lineType[, shift]]]) -> img
. @overload
.
. use `rec` parameter as alternative specification of the drawn rectangle: `r.tl() and
. r.br()-Point(1,1)` are opposite corners
其中四个参数必选：
- img：底图，uint8类型的ndarray
- pt1：矩形框的一个顶点坐标，是一个包含两个数字的tuple（必需是tuple），表示(x, y)
- pt2：pt1的对角线顶点坐标，类型同pt1
- color：颜色，是一个包含三个数字的tuple或list，表示(b, g, r)；如果图片是灰度图的话，color也可以是一个数字
其他参数说明如下：
- thickness：线宽，默认值是1，数值越大表示线宽越宽；如果取值为负数或者cv2.FILLED，那么将画一个填充了的矩形
- lineType：可以取的值有cv2.LINE_4，cv2.LINE_8，cv2.LINE_AA。其中cv2.LINE_AA的AA表示抗锯齿，线会更平滑。
注意：pt1和pt2表示任意一对对角线上的点，不一定要求pt1必需左上角，pt2必需右下角。另外pt1和pt2可以互换顺序而不影响结果。
下面是一个非交互式的程序示例
# -*- coding: utf-8 -*-
import cv2
import numpy as np
if __name__ == '__main__':
image = np.zeros((256, 256, 3), np.uint8)
color = (0, 255, 0)
cv2.rectangle(image, (20, 20), (60, 60), (0, 255, 0))
cv2.rectangle(image, (120, 120), (80, 80), (255, 0, 0), thickness=-1)
cv2.rectangle(image, (140, 200), (200, 140), (0, 0, 255), thickness=5)
cv2.namedWindow('rect', 1)
cv2.imshow('rect', image)
cv2.waitKey(0)
cv2.destroyAllWindows()
第一个矩形框pt1 = 左上角，pt2 = 右下角
第二个矩形框pt1 = 右下角，pt2 = 左上角
第三个矩形框pt1 = 右上角，pt2 = 左下角
得到的结果如下：
利用鼠标回调函数交互式画矩形框
为了容易理解下面程序，建议先参考下面文章的例2
opencv-python鼠标画点：cv2.drawMarker()
下面程序的操作方法是：
- 鼠标左键按下开始画当前矩形框
- 移动鼠标进行绘画
- 弹起左键当前矩形框绘画结束，并把当前矩形框加入列表
- 鼠标右键按下是删除矩形框列表中的最后一个对象
编程注意事项：
- 矩形框绘画过程中需要记录一个鼠标左键按下的状态标志。常规状态下该标志设为False，鼠标移动不进行绘画；当鼠标左键按下后，标志设为True，此时移动鼠标将进入绘画状态；左键弹起后，标志恢复False。
- 为了在鼠标移动过程中实时显示绘画状态，需要不停地重置用来显示的图像，并不停地重画所有已保存的矩形框
- 矩形框的第二个点使用shrink_point获取，确保不超出图像边界
# -*- coding: utf-8 -*-
import copy
import cv2
import 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)
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()
终端输出：
pt1: x = 55, y = 68
pt2: x = 0, y = 0
pt1: x = 195, y = 60
pt2: x = 256, y = 0
pt1: x = 59, y = 192
pt2: x = 0, y = 256
pt1: x = 194, y = 190
pt2: x = 256, y = 256
pt1: x = 94, y = 111
pt2: x = 170, y = 168
结果如下：
总结
到此这篇关于python opencv鼠标画矩形框之cv2.rectangle()函数的文章就介绍到这了,更多相关opencv鼠标画矩形框cv2.rectangle()内容请搜索hwidc以前的文章或继续浏览下面的相关文章希望大家以后多多支持hwidc！
【转自：美国服务器】