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A Python script to convert SVGs into React components

I've been working on a project the past few months for a team of doctors at the KU Medical Center -- Dr. Garth Fraga, Dr. Arlette-Habashi and Matt DaCunha, a third-year medical student. We're making RightSite, an iOS application aimed at reducing biopsy-labeling errors in the clinical setting.

The app is comprised of about 30 different images of the human body, which users can click on to see the anatomically correct labeling.

I use Adobe Illustrator to make the interactive overlays for the illustrations. I export the overlay as an SVG, which I then use to create a React Native SVG component. Unfortunately, the conversion from SVG to React Component is quite tedious. Removing useless defs and styles, uppercasing all the different shapes, removing the underscores between the path IDs -- all the stuff that makes your wrist ache and eyes glaze over. So I invested an afternoon to automate the conversion. The result: 50 lines of Python I wish I had wrote at the beginning of this project.

import sys
import re

def caps(str):
    str = str.replace("_1_\"","\")}")
    str = str.replace("_2_\"","\")}")
    str = str.replace("_3_\"","\")}")
    str = str.replace("_"," ")
    str = str.replace("fill-rule=\"evenodd\" clip-rule=\"evenodd\"","")
    #XX used as marker for addProps function
    str = str.replace("fill=\"#2895B2\"", "XX")
    str = str.replace("path","Path")
    str = str.replace("ellipse","Ellipse")
    str = str.replace("rect", "Rect")
    str = str.replace("polyline","Polyline")
    str = str.replace("circle","Circle")
    return str

def createTag(str):
    w = matches[2][:-2]
    h = matches[3][:-2]
    vb = matches[4]
    return( "<Svg width=\"" + w + "\" "+"height=\"" + h + "\" " + "viewBox=\"" + vb + "\">\n" )

def addProps(str):
    id = matches[0]
    str = str.replace("id=","onPressIn={() => this._appendEvent(")
    injection = "fill={consts.defaultFill} fillOpacity={this.state.selected == \""+ id + "\" ? consts.selected : consts.visible}"
    str = str.replace("XX",injection)
    return str

def main():
    output = open(sys.argv[2],"w+")
    with open(sys.argv[1],"r") as input:
        f = input.readlines()[7:-1]
        #opening tag
        output.write( createTag(f[0]) )
        lineno = 0
        for line in f:
            if lineno > 3:
                line = caps(line)
                if line[0] == '<':
                    line = addProps(line)
            lineno += 1
        #closing tag

if __name__ == "__main__":

Looking at the program function by function:

  • caps(str): remove Adobe Illustrator layer name suffixes and underscores (e.g. "SomeLayer_1" become s"Some Layer"). Uppercase all SVG elements.
  • createTag(str): create the opening opening tag for the react-native-svg component. The raw SVG export from Adobe contains a line like this:
"x="0px" y="0px" width="180px" height="626px" viewBox="-0.5 -0.3 180 626"

We care about the quoted values, which are used within the tag. Python's regular expressions are very handy for this.

  • addProps(str): Create the onPress function and "inject" style values into the individual SVG elements. This allows user to interact with the individual components of the SVGs. Another example line:
<path id="Fifth_right_distal_plantar_toe_1_" fill-rule="evenodd" clip-rule="evenodd" fill="#2895B2" d="..."/>

First, we convert the id variable into the OnPressIn function using a simple replace call. Next, create the "injection" string containing the style values, and insert this into the tag using the "XX" string that was inserted in the caps() function earlier.

  • main(): open the input SVG and write to the output SVG using the functions above. To run this script from the CLI:

The <INPUT_SVG> will be parsed, and the finished file will be written to <OUTPUT_SVG> in the same directory. If it does not already exist, the <OUTPUT_SVG> file will be created automatically (no need to make an empty SVG file to pass in).

Main tosses out the top 8 lines of the input SVG. It is useless within the react-native-svg component. After creating the opening tag, the remainder of the file is processed. The addProps() function is called if an "<" opening tag is encountered; all other lines are written to the output without change.

Performing the SVG conversions by hand isn't a broken process, but it is woefully inefficient. And inefficient processes are bad. But I always grapple.

Is it worth it to take a day and address this inefficiency? I have a lot of other shit to do.

Let this script serve to show: it most definitely IS worth it. Eliminate repetitive tasks by keeping a keen eye for automation opportunities in your workflows.

P.S. See this post on why to use onPressIn() instead of OnPress() to ensure the user interactions will work correctly Apple phones with 3D touch.