Patent ID: 7545417

Claim:
An image processing apparatus comprising: image capturing means for capturing temporally sequential images; calculating means for calculating weights of a plurality of luminance distributions by determining, in units of one or a plurality of pixels of the image captured by the image capturing means, whether the luminance of the one or the plurality of pixels belongs to any of the plurality of luminance distributions and by gradually increasing the weight of the luminance distribution to which the luminance belongs and gradually decreasing the weights of the other luminance distributions; classifying means for classifying a temporal change state of the luminance of the one or the plurality of pixels into a plurality of classes on the basis of the weights of the luminance distributions calculated by the calculating means, the plurality of classes including at least a stable class in which the luminance of the one or the plurality of pixels is stable within a predetermined range, an unstable class in which the luminance distribution to which the luminance of the one or the plurality of pixels belongs is difficult to be determined, and an intermediate class between the stable class and the unstable class; class transition determining means for determining temporal transition of the luminance change state classified by the classifying means in units of the one or the plurality of pixels; reference luminance value updating means for updating a reference luminance value of the one or the plurality of pixels in accordance with elapse of time by obtaining a representative luminance value of the luminance distribution having the largest weight when a temporal change state of the luminance of the one or the plurality of pixels belongs to the stable class; change-of-luminance detecting means for detecting whether the luminance of the one or the plurality of pixels has changed by comparing the reference luminance value with a representative luminance value of the luminance distribution having the largest weight among the plurality of luminance distributions at a change-of-luminance detection timing, the change-of-luminance detection timing being a time point when the class changes to the stable class from the unstable class through the intermediate class in the temporal transition determined by the class transition determining means; and detected change storing means for storing information to identify a position of the one or the plurality of pixels in the image where a change has occurred and information about the time when the change occurred when the change-of-luminance detecting means detects a change of the luminance, wherein an image portion that has appeared in the image and stopped there or that has disappeared from the image with elapse of time is detected on the basis of the information stored in the detected change storing means.