چکیده (انگلیسی):

The motivation of the proposed compression method is to reduce
the bit rate for image transmission or memory requirement for image
storage while maintaining image quality. The edges are one of the
prominent features in an image and they are essential for maintaining
image quality. JPEG compression standards like JPEG98 and JPEG2000
produce visual artifacts in reconstructed image at low bit rate because,
they didn’t tailored about the detailed information like edges. Hence
second generation coding introduced to preserve edge information, in
which approximation and detailed information are separately encoded,
so that, it introduces additional computational time and complexity. A
multi directional anisotropic shearlet transform provides an optimally
efficient representation of images with edges whereas wavelet transform
have limited capability in dealing with edge information in all
directions. Here, multidirectional transform called extended shearlet
transform is used to uncorrelate the input gray level values with edge
preserving capabiltiy. Hard thresholding method is applied to transform
coefficients and finally threshold output is encoded using Set
Partitioning In Hierarchical Trees (SPIHT) technique. The comparative
analysis is performed between Edge Preserved Wavelet Transform
coding (EPWT) and the extended shearlet transform coding. Image
quality is measured objectively using peak signal-to-noise ratio,
Structural Similarity Index (SSIM) and subjectively, using perceived
image quality. The simulation results show that, the extended shearlet
based compression technique is more efficient than EPWT coding
technique for wide range of geometrical features of the images.
Quantitative analysis on standard test images show that the proposed
technique outperforms the EPWT coding technique by 0.16 to 1.46 dB
of PSNR with less computational time.