QGIS » QGIS Application

I want copy some drawing in a old map to qgis
To do this
1: I turn aaa.jpg(old map) into bbb.png (export georeferenced raster) through freehand raster georeferencer plugin
2: Add raster ayer bbb.png then "Raster>Conversion>Polygonize(raster to vector)" ---default run
3: Execution failed

error:

GDAL command output:
Traceback (most recent call last):
File "D:/PROGRA~3/QGIS3~1.4/apps/qgis/./python/plugins\processing\algs\gdal\GdalAlgorithm.py", line 133, in processAlgorithm
GdalUtils.runGdal(commands, feedback)
File "D:/PROGRA~3/QGIS3~1.4/apps/qgis/./python/plugins\processing\algs\gdal\GdalUtils.py", line 110, in runGdal
for line in proc.stdout:
File "D:\PROGRA~3\QGIS3~1.4\apps\Python37\lib\codecs.py", line 322, in decode
(result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xd5 in position 487: invalid continuation byte

Execution failed after 0.53 seconds