In this paper we propose a novel framework to obtain a very compact image signature (32 bits) which is invariant to rotation, translation, scaling and other minor perturbations like smoothing, random noise addition, JPEG compression etc. The framework involves Fourier-Mellin transform, conventional PCA and non-uniform scalar quantization. The high retrieval efficiency and low space consumption demonstrates the significance of our signature in duplicate image retrieval and large image database indexing.