Skip to content

OpenCV:Drawing

APIs

  • cv2.arrowedLine
  • cv2.circle
  • cv2.clipLine
  • cv2.drawContours
  • cv2.drawMarker
  • cv2.ellipse2Poly
  • cv2.ellipse
  • cv2.fillConvexPoly
  • cv2.fillPoly
  • cv2.getFontScaleFromHeight
  • cv2.getTextSize
  • cv2.line
  • cv2.polylines
  • cv2.putText
  • cv2.rectangle

Tips

Examples

LineType

lineType 인자에 대한 내용. 거두절미하고 그림으로 확인:

Opencv_drawing_linetype.png

  • <span style="color: yellow;">yellow = cv2.LINE_4
  • <span style="color: red;">red = cv2.LINE_AA
  • <span style="color: green;">green = cv2.LINE_8

Arrows 

#include <iostream>
#include <string>

#include <opencv2/opencv.hpp>
#include <highgui.h>

using namespace std;
using namespace cv;

int main(int argc, char* argv[])
{   
   auto width = 320;
   auto height = 320;
   auto img = cv::Mat(cv::Size(width, height), CV_8UC3); // create background image

   auto center = cv::Point(width / 2, height / 2); // center point

   int lineType = 8;
   int thickness = 1;
   double tipLength = 0.1;

   img.setTo(0);                          // clear image - set to black

   for (int angle = 0; angle < 360; angle += 15)
   {
      auto angleRad = angle*CV_PI / 180.0;   // convert angle to radians

      auto length = 150;
      auto direction = cv::Point(length * cos(angleRad), length * sin(angleRad)); // calculate direction
      tipLength = .01 + 0.4 * (angle%180) / 360;

      cv::arrowedLine(img, center +direction*0.5, center + direction, CV_RGB(255, angle, 0), thickness, lineType, 0, tipLength); // draw arrow!

      ++thickness;
      if (0 == angle % 45)
         thickness = 0;

      if (180 <= angle)
         lineType = CV_AA;
   }
   imshow('Arrowed Image', img);          // show image
   waitKey();

   return EXIT_SUCCESS;
}

Python example 

import numpy as np
import cv2

# Create a black image
img = np.zeros((512,512,3), np.uint8)

# Draw a diagonal blue line with thickness of 5 px
cv2.line(img,(0,0),(511,511),(255,0,0),5)

# Drawing Rectangle
cv2.rectangle(img,(384,0),(510,128),(0,255,0),3)

# Drawing Circle
cv2.circle(img,(447,63), 63, (0,0,255), -1)

# Drawing Ellipse
cv2.ellipse(img,(256,256),(100,50),0,0,180,255,-1)

# Drawing Polygon
pts = np.array([[10,5],[20,30],[70,20],[50,10]], np.int32)
pts = pts.reshape((-1,1,2))
cv2.polylines(img,[pts],True,(0,255,255))

# Fill Polygon
pts = np.array([[320, 245], [410, 315], [380, 415], [265, 415], [240, 315]], np.int32)
pts = pts.reshape((-1, 1, 2))
cv.fillPoly(img, [pts], (0, 255, 255))  

# Adding Text to Images:
font = cv2.FONT_HERSHEY_SIMPLEX
cv2.putText(img,'OpenCV',(10,500), font, 4,(255,255,255),2,cv2.LINE_AA)

Text Box example 

font_scale = 1
font = cv2.FONT_HERSHEY_SIMPLEX
thickness = 2

for obj in self.objects:
    # obj: DetectorObject

    x, y, w, h = obj.bbox
    background = invert_color(obj.color)
    cv2.rectangle(self.preview, (x, y), (x + w, y + h), background, thickness, cv2.LINE_AA)

    text = '{} ({:.3f})'.format(obj.name, obj.score)
    text_size = cv2.getTextSize(text, font, font_scale, thickness)
    tw, th = text_size[0]
    base_line = text_size[1]
    cv2.rectangle(self.preview, (x, y), (x+tw, y-th-base_line-(thickness*2)), background, cv2.FILLED)
    cv2.putText(self.preview, text, (x, y-base_line), font, font_scale, obj.color, thickness, cv2.LINE_AA)

    if obj.points:
        cv2.drawContours(self.preview, obj.points, -1, background, 2, cv2.LINE_AA)

Blending images 

from __future__ import print_function
import cv2 as cv
alpha = 0.5
try:
    raw_input          # Python 2
except NameError:
    raw_input = input  # Python 3
print(''' Simple Linear Blender
-----------------------
* Enter alpha [0.0-1.0]: ''')
input_alpha = float(raw_input().strip())
if 0 <= alpha <= 1:
    alpha = input_alpha
# [load]
src1 = cv.imread(cv.samples.findFile('LinuxLogo.jpg'))
src2 = cv.imread(cv.samples.findFile('WindowsLogo.jpg'))
# [load]
if src1 is None:
    print("Error loading src1")
    exit(-1)
elif src2 is None:
    print("Error loading src2")
    exit(-1)
# [blend_images]
beta = (1.0 - alpha)
dst = cv.addWeighted(src1, alpha, src2, beta, 0.0)
# [blend_images]
# [display]
cv.imshow('dst', dst)
cv.waitKey(0)
# [display]
cv.destroyAllWindows()

Favorite site