09-python opencv 绘制简单图形
09-python opencv 绘制简单图形概述实现过程引用与创建空图绘制直线绘制矩形绘制圆绘制椭圆添加文字显示图像 源代码运行结果参考概述
本节实现的是使用OpenCV里自带的函数，绘制直线、长方形、圆形和椭圆。
绘制直线绘制长方形绘制圆形绘制椭圆添加文字
实现过程
引用与创建空图
不再赘述，代码如下。
import cv2 import numpy# empty imageimg = np.zeros((512, 512, 3), np.uint8)
绘制直线
使用opencv自带的line()函数绘制一条对角线，其声明如下：
cv2.line(img, pt1, pt2, color[, thickness[, lineType[, shift]]])
其中各种参数的意义如下：
-img– Image.
-pt1– First point of the line segment.
-pt2– Second point of the line segment.
-color– Line color.
-thickness– Line thickness.
-lineType– Type of the line:
-shift– Number of fractional bits in the point coordinates.
在本文中，我绘制的直线从(0,0)到(511,511)，线的颜色为蓝色(255,0,0)，粗细为10，其他参数省略。
# draw a linecv2.line(img, (0,0), (511,511), (255, 0, 0), 10)
绘制矩形
利用opencv自带的rectangle()函数可以绘制一个长方形，其声明如下：
cv2.rectangle(img, pt1, pt2, color[, thickness[, lineType[, shift]]])
其中各种参数的意义如下：
-img– Image.
-pt1– Vertex of the rectangle.
-pt2– Vertex of the rectangle opposite to pt1 .
-rec– Alternative specification of the drawn rectangle.
-color– Rectangle color or brightness (grayscale image).
-thickness– Thickness of lines that make up the rectangle. Negative values, like CV_FILLED , mean that the function has to draw a filled rectangle.
-lineType– Type of the line. See the line() description.
-shift– Number of fractional bits in the point coordinates.
本文中绘制一个长方形从(0,0)到(255,255)，设置线的颜色为绿色(0,255,0)，线的粗细为5，其他参数默认，如下：
# draw a rectanglecv2.rectangle(img, (0,0), (255,255), (0, 255, 0), 5)
绘制圆
opencv里自带的circle()函数可以绘制以一个点为圆心特定半径的圆，其函数的声明如下：
cv2.circle(img, center, radius, color[, thickness[, lineType[, shift]]])
其中各个参数的意义如下：
-img– Image where the circle is drawn.
-center– Center of the circle.
-radius– Radius of the circle.
-color– Circle color.
-thickness– Thickness of the circle outline, if positive. Negative thickness means that a filled circle is to be drawn.
-lineType– Type of the circle boundary. See the line() description.
-shift– Number of fractional bits in the coordinates of the center and in the radius value.
本文中绘制的圆的圆心为(255,255)，半径为127，线的颜色为红色，线的粗细为8，如下：
# draw a circlecv2.circle(img, (255, 255), 127, (0, 0, 255), 8)
绘制椭圆
调用ellipse()函数绘制椭圆，其声明为：
cv2.ellipse(img, center, axes, angle, startAngle, endAngle, color[, thickness[, lineType[, shift]]])
其中各个参数的意义如下：
-img– Image.
-center– Center of the ellipse.
-axes– Half of the size of the ellipse main axes.
-angle– Ellipse rotation angle in degrees.
-startAngle– Starting angle of the elliptic arc in degrees.
-endAngle– Ending angle of the elliptic arc in degrees.
-box– Alternative ellipse representation via RotatedRect or CvBox2D. This means that the function draws an ellipse inscribed in the rotated rectangle.
-color– Ellipse color.
-thickness– Thickness of the ellipse arc outline, if positive. Otherwise, this indicates that a filled ellipse sector is to be drawn.
-lineType– Type of the ellipse boundary. See the line() description.
-shift– Number of fractional bits in the coordinates of the center and values of axes.
本文绘制了一个完整的椭圆，中心在(255,255)，长轴150，短轴75，旋转0°，起始角度0°，终止角度360°，线的颜色为黄色(0,255,255)，粗细为1。
# draw a ellipsecv2.ellipse(img, (255, 255), (150, 75), 0, 0, 360, (0, 255, 255), 1)
添加文字
opencv里的自带函数putText()可以在图像上加上文字，其声明如下：
cv2.putText(img, text, org, fontFace, fontScale, color[, thickness[, lineType[, bottomLeftOrigin]]])
各个参数的意义如下：
-img– Image.
-text– Text string to be drawn.
-org– Bottom-left corner of the text string in the image.
-font– CvFont structure initialized using InitFont().
-fontFace– Font type. One of FONT_HERSHEY_SIMPLEX, FONT_HERSHEY_PLAIN, FONT_HERSHEY_DUPLEX, FONT_HERSHEY_COMPLEX, FONT_HERSHEY_TRIPLEX, FONT_HERSHEY_COMPLEX_SMALL, FONT_HERSHEY_SCRIPT_SIMPLEX, or FONT_HERSHEY_SCRIPT_COMPLEX, where each of the font ID’s can be combined with FONT_ITALIC to get the slanted letters.
-fontScale– Font scale factor that is multiplied by the font-specific base size.
-color– Text color.
-thickness– Thickness of the lines used to draw a text.
-lineType– Line type. See the line for details.
-bottomLeftOrigin– When true, the image data origin is at the bottom-left corner. Otherwise, it is at the top-left corner.
本文在图像上显示OpenCV这几个字，如下：
font=cv2.FONT_HERSHEY_SIMPLEXcv2.putText(img,'OpenCV',(10,500), font, 4,(255,255,255),2)
显示图像
显示最终绘制完的图像：
# show imagecv2.imshow("shape", img)cv2.waitKey(0)cv2.destroyAllWindows()
源代码
整个程序的源代码如下：
# created by Huang Lu# 27/08/ 17:59:31 # Department of EE, Tsinghua Univ.import cv2import numpy as np# empty imageimg = np.zeros((512, 512, 3), np.uint8)# draw a linecv2.line(img, (0,0), (511,511), (255, 0, 0), 10)# draw a rectanglecv2.rectangle(img, (0,0), (255,255), (0, 255, 0), 5)# draw a circlecv2.circle(img, (255, 255), 127, (0, 0, 255), 8)# draw a ellipsecv2.ellipse(img, (255, 255), (150, 75), 0, 0, 360, (0, 255, 255), 1)# add textfont=cv2.FONT_HERSHEY_SIMPLEXcv2.putText(img,'OpenCV',(10,500), font, 4,(255,255,255),2)# show imagecv2.imshow("shape", img)cv2.waitKey(0)cv2.destroyAllWindows()
也可以参考我的GitHub上的，点击这里。
运行结果
在命令行进入该源程序所在目录后，运行python main.py后即可显示结果。显示结果如下：
