做圖像識別的時候需要在圖片中畫出特定大小和角度的矩形框，自己寫了一個函數，給定的輸入是圖片名稱，矩形框的位置坐標,長寬和角度，直接輸出畫好矩形框的圖片。

主要思想是先根據x,y坐標和長寬得到矩形，然后通過數學計算得到旋轉angle角度后的新矩形框的四個頂點位置坐標，再利用draw.line()函數畫出來。

import mathimport matplotlib.pyplot as pltimport numpy as npfrom PIL import Image, ImageDrawdef 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()

改寫成c++

由于c++程序也需要用到這個程序，改寫一下

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("未打開圖片不能分析"));    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); //將Cstring轉成float類型  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("圖片已修改/r/n"));}