Typically searching image collections is based on features of the images. In most cases the features are based on the color histogram of the images. Similarity search based on color histograms is very efficient, but the quality of the search results is often rather poor. One of the reasons is that histogram-based systems only support a specific form of global similarity using the whole histogram as one vector. But there is more information in a histogram than the distribution of colors. This paper has two contributions: (1) a new generalized similarity search method based on a wavelet transformation of the color histograms and (2) a new effectiveness measure for image similarity search. Our generalized similarity search method has been deve...