The present invention relates to a blue sky color detection technique. 
Sky is an important subject matter seen in photographic images.  The identification of sky in images facilitates its enhancement and image manipulation. 
The most prominent characteristic of sky tends to be its color, which is usually light blue when the sky is clear.  Such a characteristic has been used to detect sky in images. 
There exists conventional techniques of enhancing the color of a color image.  One technique involves image-dependent color saturation correction in a natural scene pictorial image disclosed in U.S. Pat.  No.  5,450,217.  In this method, color saturation is enhanced in an HSV color space, which is considered as being capable of representing an image to have almost the same saturation as a recognized saturation of the image.  However, this method can enhance the color saturation of certain images only, which have an average saturation of no higher than a certain threshold value. 
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.