Image Resizing and Other applications Jayanta Mukhopadhyay Department of Computer Science & Engineering Indian Institute of Technology, Kharagpur, 721302, India jay@cse.iitkgp.ernet.in

Image Down-Sampling 8x8 block Sub-band Approx. Block Composition LxM 8x8 blocks Block Composition Larger DCT blocks 8x8 block Sub-band Approx.

Image Up-Sampling LxM 8x8 blocks Block Decompos. Sub-band Approx. Larger DCT blocks 8x8 block Block Decompos.

Image Up-Sampling: A different Strategy A few 8x8 blocks Sub-band Approx. Block Decompos. 8x8 block Smallaer DCT blocks

Some results related to image halving and image doubling

Comparative performance   Images PSNR (dB)‏ DA SB TR Lena Watch Cap F-16 34.64 29.26 34.33 32.43 34.83 29.57 32.70 34.95 29.72 34.37 32.82 PSNR values after halving and doubling a grey level image. Mukherjee, Mitra (2002) , IEEE CSVT

Comparative performance   Images PSNR (dB) DA SB TR Lena Peppers Baboon 33.82 26.39 22.90 34.00 26.54 22.87 34.09 26.59 22.88 PSNR values after halving and doubling a color image.

Comparative performance Lena Peppers PSNR plots for different techniques at varying compression ratio for color images

Images (a) (b) (c) Reconstructed images by (a) DA (b) SB and (c) TR

Images (a) (b) (c) Reconstructed images by (a) DA (b) SB and (c) TR

Arbitrary Resizing: Some examples Mukherjee and Mitra (2005), IEE VISP

2x3 Down-Sampling

2x3 Up-Sampling

HDTV Format

NTSC Format

Color Image resizing: An Example 2x3 Down-sampling

2x3 Up-Sampling

Frajka and Zegar, SP and IC, 2004. Wavelet Resizing Frajka and Zegar, SP and IC, 2004.

Up-sampling and Down-sampling in the DCT domain

DCT domain Upsampling with Zero Insertion Type-II DCT of upsampled signal as obtained through zero insertion of signal x(n) is computed by: Note:- DCT obtained is referred as upsampled DCT.

A typical conversion matrix 4x4 block to 8x8 upsampled type-II DCT For even sample xoxoxoxo… For odd sample oxoxoxox…

Downsampling from block DCT For LL subband For LH subband

DCT-Wavelet Downsampling

Transcoding Matrix for downsampling Ttd

Upsampling

Transcoding Matrix for upsampling Tu

Results: Resizing with threshold Cost of resizing with input/output representation in block DCT domain

Resizing Results Poor Performance

Resizing Results Original DWT on Image (Downsampling)

Resizing Results Wavelet upsampling Proposed upsampling PSNR=35.28 dB, JPQM=9.86 Proposed upsampling PSNR=35.28 dB, JPQM=9.65

Resizing Results DCT upsampl ing Bilinear upsampling PSNR=29.96 dB, JPQM=7.86 Bilinear upsampling PSNR=29.74dB, JPQM=9.23

Resizing Results Non-sparse data PSNR=35.19 dB Sparse data

Extraction of ROI

Extraction of ROI from an image in the DCT domain If a 8x8 block is totally contained in ROI, output it as it is. If a 8x8 block is totally outside of ROI, set DCT values to ZERO. For a mixed 8x8 block, perform quad-tree decomposition. Retain the coefficients if a leaf node is totally contained in ROI, else discard it. Recompose the decomposed nodes to a 8x8 block following the same quad-tree partitioning.

ORGINAL IMAGE

BINARY OF REGION OF INTEREST

EXTRACTED IMAGE

ORIGINAL IMAGE

BINARY OF REGION OF INTEREST   BINARY OF REGION OF INTEREST

EXTRACTED IMAGE

Logo insertion

Insertion of a logo in the DCT domain Form an image (called as logo-image) of same size with the logo placed in desired location. The rest of the pixels are set to zero. Partition the logo-image in 8x8 blocks. If all the pixels of a block belong to the logo, perform 8x8 DCT of that block and replace the corresponding DCT block. If a ZERO block of logo-image is totally contained in the DCT block of the given image. Output the corresponding DCT block of the given image.

(contd.) For a mixed block, perform multilevel decomposition following a quad-tree. Retain the DCT coefficients of either from the given image or from the logo-image according to the homogeneous property of its leaf-node. Recompose the multilevel-decomposed coefficients to a 8x8 DCT block.

ORIGINAL IMAGE

LOGO TO BE INSERTED

ORIGINAL IMAGE WITH LOGO INSERTED

ORIGINAL IMAGE WITH LOGO INSERTED

IMAGE WITH LOGO INSERTED

Thanks

where, Type I 2D-DCT Type-I 2-D DCT of a block

  Type II 2D-DCT     X k ,     Type-II 2-D DCT of a block N  1 N  1            ( k )‏  (  )‏ x m , n cos 2 m  1    k cos 2 n  1   , where, N 2 N 2 N m  n   k ,   N  1