Transform image coding with global thresholding: application to baseline JPEG

Many image compression schemes perform the discrete cosine transform (DCT) to represent an image in frequency space. An analysis of a suite of images confirms that the luminance AC coefficients can be modeled by a Laplacian distribution. The distribution model can be used to drop the insignificant coefficients. In this paper we develop an image-adaptive JPEG encoding algorithm that incorporates global thresholding and near optimal quantization approach based on Lagrangian multiplier. Simulation results demonstrate that, with our thresholding technique, we can improve the reconstructed image quality compared to the one provided by other DCT image coding schemes without thresholding