  A procedure is introduced to recognise sunspots automatically in solar
full-disk photosphere images obtained from Huairou Solar Observing Station,
National Astronomical Observatories of China. The images are first
pre-processed through Gaussian algorithm. Sunspots are then recognised by the
morphological Bot-hat operation and Otsu threshold. Wrong selection of sunspots
is eliminated by a criterion of sunspot properties. Besides, in order to
calculate the sunspots areas and the solar centre, the solar limb is extracted
by a procedure using morphological closing and erosion operations and setting
an adaptive threshold. Results of sunspot recognition reveal that the number of
the sunspots detected by our procedure has a quite good agreement with the
manual method. The sunspot recognition rate is 95% and error rate is 1.2%. The
sunspot areas calculated by our method have high correlation (95%) with the
area data from USAF/NOAA.
