pyocr报错convert-im6.q16: not authorized

按照下面的操作进行Python的OCR文字识别（识别PDF文字）
https://pythontips.com/2016/02/25/ocr-on-pdf-files-using-python/
http://blog.topspeedsnail.com/archives/3571

运行出现错误

wand.exceptions.PolicyError: not authorized `/tmp/xxx.pdf' @ .......

wand未授权，这是wand所调用ImageMagick的配置问题，需要修改/etc/ImageMagick-6/policy.xml文件

sudo vi /etc/ImageMagick-6/policy.xml

找到

<policy domain="coder" rights="none" pattern="PDF" />

修改为

<policy domain="coder" rights="read|write" pattern="PDF" />

除了PDF，其它类型文件也会出现这种错误，修改相应的条目就好了

<policy domain="cache" name="shared-secret" value="passphrase"/>
  <policy domain="coder" rights="none" pattern="EPHEMERAL" />
  <policy domain="coder" rights="none" pattern="URL" />
  <policy domain="coder" rights="none" pattern="HTTPS" />
  <policy domain="coder" rights="none" pattern="MVG" />
  <policy domain="coder" rights="none" pattern="MSL" />
  <policy domain="coder" rights="none" pattern="TEXT" />
  <policy domain="coder" rights="none" pattern="SHOW" />
  <policy domain="coder" rights="none" pattern="WIN" />
  <policy domain="coder" rights="none" pattern="PLT" />
  <policy domain="path" rights="none" pattern="@*" />
  <!-- disable ghostscript format types -->
  <policy domain="coder" rights="none" pattern="PS" />
  <policy domain="coder" rights="none" pattern="EPS" />
  <policy domain="coder" rights="read|write" pattern="PDF" />
  <policy domain="coder" rights="none" pattern="XPS" />

参考:
https://stackoverflow.com/questions/53442110/convert-not-authorized-tieps-error-constitute-c-readimage-412
https://blog.csdn.net/m0_37566460/article/details/86007287