python实现在图片上画特定大小角度矩形框

做图像识别的时候需要在图片中画出特定大小和角度的矩形框，自己写了一个函数，给定的输入是图片名称，矩形框的位置坐标,长宽和角度，直接输出画好矩形框的图片。

主要思想是先根据x,y坐标和长宽得到矩形，然后通过数学计算得到旋转angle角度后的新矩形框的四个顶点位置坐标，再利用draw.line()函数画出来。

import math

import matplotlib.pyplot as plt
import numpy as np
from PIL import Image, ImageDraw

def draw(filename,result):
 img = Image.open(filename)
 w,h=img.size
 draw = ImageDraw.Draw(img)
 result=np.array(result)
 x=result[0][0]
 y=result[0][1]
 angle=result[0][2]
 height=result[0][3]
 width=result[0][4]

anglePi = -angle*math.pi/180.0
 cosA = math.cos(anglePi)
 sinA = math.sin(anglePi)

x1=x-0.5*width
 y1=y-0.5*height

x0=x+0.5*width
 y0=y1

x2=x1
 y2=y+0.5*height

x3=x0
 y3=y2

x0n= (x0 -x)*cosA -(y0 - y)*sinA + x
 y0n = (x0-x)*sinA + (y0 - y)*cosA + y

x1n= (x1 -x)*cosA -(y1 - y)*sinA + x
 y1n = (x1-x)*sinA + (y1 - y)*cosA + y

x2n= (x2 -x)*cosA -(y2 - y)*sinA + x
 y2n = (x2-x)*sinA + (y2 - y)*cosA + y

x3n= (x3 -x)*cosA -(y3 - y)*sinA + x
 y3n = (x3-x)*sinA + (y3 - y)*cosA + y

draw.line([(x0n, y0n),(x1n, y1n)], fill=(0, 0, 255))
 draw.line([(x1n, y1n),(x2n, y2n)], fill=(255, 0, 0))
 draw.line([(x2n, y2n),(x3n, y3n)],fill= (0,0,255))
 draw.line([(x0n, y0n), (x3n, y3n)],fill=(255,0,0))

plt.imshow(img)
 plt.show()

改写成c++

由于c++程序也需要用到这个程序，改写一下

void CopentestDlg::OnBnClickedAnaly()
{
 CString x,y,angle,width;
 float xRaw[4], yRaw[4];
 float xNew[4], yNew[4];
 float height = 33;
 if (imageCut==NULL) {
   AfxMessageBox(_T("未打开图片不能分析"));
   return;
 }
 GetDlgItem(IDC_EX)->GetWindowText(x);
 GetDlgItem(IDC_EY)->GetWindowText(y);
 GetDlgItem(IDC_ANGLE)->GetWindowText(angle);
 GetDlgItem(IDC_WIDTH)->GetWindowText(width);
 float xf = _tstof(x); //将Cstring转成float类型
 float yf = _tstof(y);
 float widthf= _tstof(width);
 float anglef= _tstof(angle);

xRaw[1] = xf - 0.5*widthf;
 yRaw[1] = yf - 0.5*height;

xRaw[0] = xf + 0.5*widthf;
 yRaw[0] = yRaw[1];

xRaw[2] = xRaw[1];
 yRaw[2] = yf + 0.5*height;

xRaw[3] = xRaw[0];
 yRaw[3] = yRaw[2];

float anglePi = -anglef*pi / 180.0;
 float cosA = cos(anglePi);
 float sinA = sin(anglePi);

xNew[0] = (xRaw[0] - xf)*cosA - (yRaw[0] - yf)*sinA + xf;
 yNew[0] = (xRaw[0] - xf)*sinA + (yRaw[0] - yf)*cosA + yf;

xNew[1] = (xRaw[1] - xf)*cosA - (yRaw[1] - yf)*sinA + xf;
 yNew[1] = (xRaw[1] - xf)*sinA + (yRaw[1] - yf)*cosA + yf;

xNew[2] = (xRaw[2] - xf)*cosA - (yRaw[2] - yf)*sinA + xf;
 yNew[2] = (xRaw[2] - xf)*sinA + (yRaw[2] - yf)*cosA + yf;

xNew[3] = (xRaw[3] - xf)*cosA - (yRaw[3] - yf)*sinA + xf;
 yNew[3] = (xRaw[3] - xf)*sinA + (yRaw[3] - yf)*cosA + yf;

cvLine(imageCut, cvPoint(xNew[0], yNew[0]), cvPoint(xNew[1], yNew[1]), cvScalar(0, 0, 255), 3);
 cvLine(imageCut, cvPoint(xNew[1], yNew[1]), cvPoint(xNew[2], yNew[2]), cvScalar(255, 0, 0), 3);
 cvLine(imageCut, cvPoint(xNew[2], yNew[2]), cvPoint(xNew[3], yNew[3]), cvScalar(0, 0, 255), 3);
 cvLine(imageCut, cvPoint(xNew[0], yNew[0]), cvPoint(xNew[3], yNew[3]), cvScalar(255, 0, 0), 3);

DrawPicToHDC(imageCut, IDC_Cut);
 pEdit->ReplaceSel(_T("图片已修改\r\n"));
}

效果图

来源：https://blog.csdn.net/u013948010/article/details/78318894