Welcome folks today in this blog post we will be converting autocad drawings to image files using dxfgrabber library in python. All the full source code of application is given below.

Get Started

In order to get started you need to install the following libraries using the pip command as shown below

pip install dxfgrabber

After installing this library make an app.py file and copy paste the following code

app.py

import dxfgrabber
import cv2
import numpy as np
import sys

"""
def absdiff(num1, num2):
    if num1 <= num2:
        return num2 - num1
    else:
        return num1 - num2
"""

def getMinXY(shapes):
    minX, minY = 99999, 99999
    for shape in shapes:
        if shape.dxftype == 'LINE':
            minX = min(minX, shape.start[0], shape.end[0])
            minY = min(minY, shape.start[1], shape.end[1])
        elif shape.dxftype == 'ARC':
            minX = min(minX, shape.center[0])
            minY = min(minY, shape.center[1])

    return minX, minY

def getMaxXY(shapes):
    maxX, maxY = -99999, -99999
    for shape in shapes:
        if shape.dxftype == 'LINE':
            maxX = max(maxX, shape.start[0], shape.end[0])
            maxY = max(maxY, shape.start[1], shape.end[1])
        elif shape.dxftype == 'ARC':
            maxX = max(maxX, shape.center[0])
            maxY = max(maxY, shape.center[1])

    return maxX, maxY

#Translate x,y values as per fourth quadrant i.e positive x and negative y. Update y value to positive, to be used by opencv axes. 
# shift origin of image by 100 pixels for better clarity of output image
def getXY(point):
    x, y = point[0], point[1]
    return int(x-minX+100), int(abs(y-maxY)+100)

dxf = dxfgrabber.readfile(sys.argv[1])
shapes = dxf.entities.get_entities()
minX, minY = getMinXY(shapes)
maxX, maxY = getMaxXY(shapes)
#baseX, baseY = absdiff(minX, 0), absdiff(minY, 0)
#absMaxX, absMaxY = absdiff(maxX, 0), absdiff(maxY, 0)


print(maxX, maxY)
print(minX, minY)
#print(absMaxX, absMaxY)
#print(baseX, baseY)


canvas = np.zeros((512,512,3), np.uint8)
for shape in shapes:
    if shape.dxftype == 'LINE':
        x1, y1 = getXY(shape.start)
        x2, y2 = getXY(shape.end)
        canvas = cv2.line(canvas, (x1,y1), (x2,y2), (255, 0, 255), 1)
    elif shape.dxftype == 'ARC':
        centerX, centerY = getXY(shape.center)        
        if (shape.start_angle > 180) and (shape.end_angle < shape.start_angle):
            canvas = cv2.ellipse(canvas, (centerX, centerY), (int(shape.radius), int(shape.radius)), 180, int(shape.start_angle) - 180, 180 + int(shape.end_angle), (0, 0, 255), 1)
        else:
            canvas = cv2.ellipse(canvas, (centerX, centerY), (int(shape.radius), int(shape.radius)), 0, int(360 - shape.start_angle), int(360 - shape.end_angle), (0, 0, 255), 1)
    cv2.imshow('test', canvas)
    cv2.waitKey(50)

cv2.imwrite('res.png', canvas)
cv2.waitKey(0)
cv2.destroyAllWindows()

Now if you run this python script app.py by typing the below command

python app.py input.dwg

Here we are providing the input file as a command line argument to the script