Describing Colors, Textures and Shapes for Content Based Image Retrieval - A Survey <s> Generic Fourier Descriptors (GFD) <s> Shape description is one of the key parts of image content description for image retrieval. Most of the existing shape descriptors are usually either application dependent or non-robust, making them undesirable for generic shape description. In this paper, a generic Fourier descriptor (GFD) is proposed to overcome the drawbacks of existing shape representation techniques. The proposed shape descriptor is derived by applying two-dimensional Fourier transform on a polar-raster sampled shape image. The acquired shape descriptor is application independent and robust. Experimental results show that the proposed GFD outperforms common contour-based and region-based shape descriptors. <s> BIB001 </s> Describing Colors, Textures and Shapes for Content Based Image Retrieval - A Survey <s> Generic Fourier Descriptors (GFD) <s> A conventional color histogram (CCH) considers neither the color similarity across different bins nor the color dissimilarity in the same bin. Therefore, it is sensitive to noisy interference such as illumination changes and quantization errors. Furthermore, CCHs large dimension or histogram bins requires large computation on histogram comparison. To address these concerns, this paper presents a new color histogram representation, called fuzzy color histogram (FCH), by considering the color similarity of each pixel's color associated to all the histogram bins through fuzzy-set membership function. A novel and fast approach for computing the membership values based on fuzzy c-means algorithm is introduced. The proposed FCH is further exploited in the application of image indexing and retrieval. Experimental results clearly show that FCH yields better retrieval results than CCH. Such computing methodology is fairly desirable for image retrieval over large image databases. <s> BIB002
These are region based descriptors. These were derived by BIB001 . The shape was first transformed to polar coordinates and then the 2D Fourier transform was applied for the derivation of the shape descriptor. GFD are calculated as BIB002 12 The GFD are invariant to scale, rotation and translation.