There are reported methods for fire or smoke recognition respectively. But in forest, fire and smoke always exist together,
and fire area lies within smoke area. Both fire and smoke are important features for fire detection. Based on this fact we
present a novel method to detect fire and smoke in two steps and obtain areas of fire and smoke together. With the help
of Otsu method taking gray value and red value as inputs, fire and smoke regions are segmented from the background,
and regions with very small areas are deleted as noises; then fire is segmented from the left large and continuous regions.
Area, roundness and contour of segmented results are used to further recognize smoke or fire from other regular objects,
or to describe the status and trend of forest fire.