For SVG files with bloated PNG embeds

xtract.py

def xtract_pngs_from_svgs(name):
    fname = name +'.svg'
    #
    with open(fname) as f:
        raw = f.read()
    #
    prefix = 'xlink:href="data:image/png;base64,'
    suffix = '"'
    chunks = []
    found = []
    pos = 0
    #
    while True:
        start = raw.find(prefix, pos)
        if start == -1:
            chunks.append(raw[pos:])
            break
        #
        startwithprefix = start+len(prefix)
        end = raw.index(suffix, startwithprefix)
        chunks.append(raw[pos:startwithprefix])
        chunks.append("REPLACEME")
        found.append(raw[startwithprefix:end])
        pos = end
    #
    blank_svg = ''.join(chunks)
    with open(name+'-blank.svg', 'w') as f:
        f.write(blank_svg)
    #
    pngs = (base64.urlsafe_b64decode(chunk) for chunk in found)
    for n, png in enumerate(pngs):
        with open(f'{name}-{n}.png', 'wb') as f:
            f.write(png)