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使用 OpenCV

在图像上绘制几何形状

原文:https://www.geesforgeks.org/draw-geometric-shapes-images-using-opencv/

OpenCV 提供了很多绘图功能，可以在图像上绘制几何形状和书写文字。让我们看看一些绘图功能，并使用 OpenCV 在图像上绘制几何形状。

一些绘图功能包括:

cv2.line() : 用于在图像上画线。 cv2.rectangle() : 用于在图像上绘制矩形。 cv2.circle() : 用于在图像上画圆。 cv2.putText() : 用于在图像上书写文字。

为了演示上述功能的使用，我们需要一个尺寸为 400 X 400 的图像，用纯色填充(本例中为黑色)。为了做到这一点，我们可以利用numpy.zeross功能来创建所需的图像。

蟒蛇 3

# Python3 program to draw solid-colored
# image using numpy.zeroes() function
import numpy as np
import cv2

# Creating a black image with 3 channels
# RGB and unsigned int datatype
img = np.zeros((400, 400, 3), dtype = "uint8")
cv2.imshow('dark', img)

# Allows us to see image
# until closed forcefully
cv2.waitKey(0)
cv2.destroyAllWindows()

输出:

image of size 400 X 400 filled with a solid color using opencv

现在，让我们在这个实心的黑色图像上画一些几何形状。

画一条线:

cv2.line(imageObjectName，(' start_coordinates ')，(' end_coordinates ')，(' color_in_bgr ')，' line_thickness ')

蟒蛇 3

# Python3 program to draw line
# shape on solid image
import numpy as np
import cv2

# Creating a black image with 3 channels
# RGB and unsigned int datatype
img = np.zeros((400, 400, 3), dtype = "uint8")

# Creating line
cv2.line(img, (20, 160), (100, 160), (0, 0, 255), 10)

cv2.imshow('dark', img)

# Allows us to see image
# until closed forcefully
cv2.waitKey(0)
cv2.destroyAllWindows()

输出:

Draw a line using opencv

画一个矩形:

cv2.rectangle(imageObjectName，(' top_left_vertex_coordinates ')，(' lower_right_vertex_coordinates ')，(' stroke_color_in_bgr ')，' stroke_thickness ')

蟒蛇 3

# Python3 program to draw rectangle
# shape on solid image
import numpy as np
import cv2

# Creating a black image with 3
# channels RGB and unsigned int datatype
img = np.zeros((400, 400, 3), dtype = "uint8")

# Creating rectangle
cv2.rectangle(img, (30, 30), (300, 200), (0, 255, 0), 5)

cv2.imshow('dark', img)

# Allows us to see image
# until closed forcefully
cv2.waitKey(0)
cv2.destroyAllWindows()

输出:

Draw a rectangle using opencv

画一个圆:

cv2.circle(imageObjectName，(' center_coordinates ')，(' circle_radius ')，(' color_in_bgr ')，' stroke_thickness ')

蟒蛇 3

# Python3 program to draw circle
# shape on solid image
import numpy as np
import cv2

# Creating a black image with 3
# channels RGB and unsigned int datatype
img = np.zeros((400, 400, 3), dtype = "uint8")

# Creating circle
cv2.circle(img, (200, 200), 80, (255, 0, 0), 3)

cv2.imshow('dark', img)

# Allows us to see image
# until closed forcefully
cv2.waitKey(0)
cv2.destroyAllWindows()

输出:

Draw a circle using opencv

书写文本:

cv2.putText(imageObjectName，' TextContent '，(' text_starting_point_coordinates ')，' fontToBeUsed '，' font_size '，(' text_color '，' text_thickness '，' line_type ')

计算机编程语言

# Python3 program to write 
# text on solid image
import numpy as np
import cv2

# Creating a black image with 3
# channels RGB and unsigned int datatype
img = np.zeros((400, 400, 3), dtype = "uint8")

# writing text
font = cv2.FONT_HERSHEY_SIMPLEX
cv2.putText(img, 'GeeksForGeeks', (50, 50),
            font, 0.8, (0, 255, 0), 2, cv2.LINE_AA)

cv2.imshow('dark', img)

# Allows us to see image
# until closed forcefully
cv2.waitKey(0)
cv2.destroyAllWindows()

输出:

writing text using opencv

在图像上绘制形状的应用:

  • 绘制几何形状可以帮助我们突出图像的特定部分。
  • 像线这样的几何形状可以帮助我们指出或识别图像中的特定区域。
  • 在图像的特定区域上书写文本可以为该区域添加描述。

参考: https://docs.opencv.org/2.4/modules/core/doc/drawing_functions.html

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