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Library to help the drawing process with OpenCV. Thought to add labels to the images. Classification of images, etc.

Project description


Library to help the drawing process with OpenCV. Thought to add labels to the images. Classification of images, etc.


Image generated with Intel Openvino Toolkit and drawed with opencv-draw-tools v0.1.9



You will need to install:

  • opencv >= 3.6.2
  • numpy >= 1.13.3
  • python-constraint >= 1.4.0

You can simply execute: pip install -r requirements.txt

Finally you can install the library with:

pip install opencv-draw-tools-fernaperg

When you install opencv-draw-tools, it will automatically download numpy but not opencv becouse in some cases you will need another version.



import opencv_draw_tools as cv2_tools

print('Name: {}\nVersion:{}\nHelp:{}'.format(,cv2_tools.__version__,

Oriented Object Programming method

Firstly create a SelectorCV2 object. You can pass it optional parameters to configure the output.

selector = cv2_tools.SelectorCV2(color=(200,90,0), filled=True)

Also you can configure it later using the method (all optional parameters):


Now, each time you want to add a selected zone call the method:


   |          |
   |          |

Tags (optional parameter):
* It could be a normal string
* A string with '\n'
* A list of strings
* None / '' / [] / False

Finally, when you want to draw all the rectangles execute:

edited_frame = selector.draw(frame)

If you want to use the same object multiple times you can easily change the content inside it:

# This method could help change rectangles to
selector.set_range_valid_rectangles( origin, destination)

# This method could help if you know exactly the indexes that you want to keep
# Default = [], so if you just want to clean the buffer call this method without parameters

If you want, you can see the example, it also use an open source library called face_recognition.

Manual method

import opencv_draw_tools as cv2_tools

  Draw better rectangles to select zones.
  Keyword arguments:
  frame -- opencv frame object where you want to draw
  position -- touple with 4 elements (x1, y1, x2, y2)
              This elements must be between 0 and 1 in case it is normalized
              or between 0 and frame height/width.
  tags -- list of strings/tags you want to associate to the selected zone (default [])
  tag_position -- position where you want to add the tags, relatively to the selected zone (default None)
                  If None provided it will auto select the zone where it fits better:
                      - First try to put the text on the Bottom Rigth corner
                      - If it doesn't fit, try to put the text on the Bottom Left corner
                      - If it doesn't fit, try to put the text Inside the rectangle
                      - Finally if it doesn't fit, try to put the text On top of the rectangle
  alpha -- transparency of the selected zone on the image (default 0.9)
           1 means totally visible and 0 totally invisible
  color -- color of the selected zone, touple with 3 elements BGR (default (110,70,45) -> dark blue)
           BGR = Blue - Green - Red
  normalized -- boolean parameter, if True, position provided normalized (between 0 and 1) else you should provide concrete values (default False)
  thickness -- thickness of the drawing in pixels (default 2)
  filled -- boolean parameter, if True, will draw a filled rectangle with one-third opacity compared to the rectangle (default False)
  peephole -- boolean parameter, if True, also draw additional effect, so it looks like a peephole
frame = cv2_tools.select_zone(frame, position, tags=[])

Example with Webcam

import opencv_draw_tools as cv2_tools

See webcam_test() code:

def webcam_test():
    """Reproduce Webcam in real time with a selected zone."""
    print('Launching webcam test')
    cap = cv2.VideoCapture(0)
    f_width = cap.get(3)
    f_height = cap.get(4)
    window_name = 'opencv_draw_tools'
    while True:
        ret, frame =
        frame = cv2.flip(frame, 1)
        if ret:
            keystroke = cv2.waitKey(1)
            position = (0.33,0.2,0.66,0.8)
            tags = ['MIT License', '(C) Copyright\n    Fernando\n    Perez\n    Gutierrez']
            frame = select_zone(frame, position, tags=tags, color=(130,58,14), thickness=2, filled=True, normalized=True)
            cv2.imshow(window_name, frame)
            # True if escape 'esc' is pressed
            if keystroke == 27:

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