问‘'jpeg’是不支持的格式错误

EN

def pdf_page_to_png(src_pdf, pagenum=0, resolution=300, slug=''):
    dst_pdf = PyPDF2.PdfFileWriter()
    dst_pdf.addPage(src_pdf.getPage(pagenum))

    pdf_bytes = io.BytesIO()
    dst_pdf.write(pdf_bytes)
    pdf_bytes.seek(0)

    img = Image(file=pdf_bytes, resolution=resolution)
    img.convert("jpeg")

    if pagenum == 0:
        os.makedirs('media/einsert/%s' % slug)

    img.save(filename='media/einsert/%s/page_%s.jpeg' % (slug, pagenum))

    return img

/Users/daro/praca/polsha24/lib/python2.7/site-packages/wand/image.py in format
    def format(self, fmt):
        if not isinstance(fmt, string_type):
            raise TypeError("format must be a string like 'png' or 'jpeg'"
                            ', not ' + repr(fmt))
        fmt = fmt.strip()
        r = library.MagickSetImageFormat(self.wand, binary(fmt.upper()))
        if not r:
                        raise ValueError(repr(fmt) + ' is unsupported format') ...
        r = library.MagickSetFilename(self.wand,
                                      b'buffer.' + binary(fmt.lower()))
        if not r:
            self.raise_exception()
    @property