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Image Resizing and Other applications

Jayanta MukhopadhyayDepartment of Computer Science & Engineering

Indian Institute of Technology, Kharagpur, 721302, India

jay@cse.iitkgp.ernet.in

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Image Down-Sampling

LxM8x8 blocks

BlockComposition

Larger DCT blocks

8x8 block

Sub-bandApprox.

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Image Up-Sampling

LxM8x8 blocks

Sub-bandApprox.

Larger DCT blocks8x8 block

BlockDecompos.

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Image Up-Sampling: A different Strategy

A few8x8 blocks

Block Decompos.

Smallaer DCT blocks

8x8 block

Sub-bandApprox.

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Some results related to image halving and image doubling

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Comparative performance

 Images

PSNR (dB)

DA SB TR

LenaWatchCapF-16

34.6429.2634.3332.43

34.8329.5734.3332.70

34.9529.7234.3732.82

PSNR values after halving and doubling a grey level image.

Mukherjee, Mitra (2002) , IEEE CSVT

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PSNR values after halving and doubling a color image.

 Images

PSNR (dB)

DA SB TR

LenaPeppersBaboon

33.8226.3922.90

34.0026.5422.87

34.0926.5922.88

Comparative performance

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Comparative performance

PSNR plots for different techniques at varying compression ratio for color images

Lena Peppers

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Arbitrary Resizing: Some examples

Mukherjee and Mitra (2005), IEE VISP

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2x3 Down-Sampling

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2x3 Up-Sampling

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HDTV Format

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NTSC Format

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Color Image resizing: An Example

2x3 Down-sampling

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2x3 Up-Sampling

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Wavelet Resizing

D o w ns a m ple d im a g e

ID W TL L

L L O

O OIM A G E

W a ve le ts ubba nds

U pa s m ple dim a g e

W a ve le t D o ubling

IM A G E LLLL H L

LH H H

D o w ns a m ple d im a g e

D W T

W a ve le ts ubba nds

W a ve le t H a lving

Frajka and Zegar, SP and IC, 2004.

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Up-sampling and Down-Up-sampling and Down-sampling in the DCT domainsampling in the DCT domain

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DCT domain Upsampling with Zero Insertion

Type-II DCT of upsampled signal as obtained throughzero insertion of signal x(n) is computed by:

Note:- DCT obtained is referred as upsampled DCT.

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A typical conversion matrix4x4 block to 8x8 upsampled type-II DCT

For even sample xoxoxoxo…

For odd sampleoxoxoxox…

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For LLsubba

nd

For LH

subband

Downsampling from block DCT

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DCT-Wavelet Downsampling

LL

D o w ns a m ple d im a g e

B W T

D o w ns a m ple dim a g e D C T blo c k s

D C T

Im a g eD C T blo c k s

D C T -W a ve le t

LL s ubba nd tra ns c o ding

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Transcoding Matrix for downsampling

Ttd

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Upsampling

D o w ns a m ple dim a g e D C T blo c k s

LLID C T W B D T

U ps a m ple d im a g eD C T blo c k s

D o w ns a m ple d im a g e

W a ve le t-D C T

LL s ubba nd tra ns c o ding

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Transcoding Matrix for upsampling

TTuu

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Results: Resizing with threshold

Cost of resizing with input/output representation in block DCT domain

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Resizing Results

Poor Performance

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Resizing Results

Original DWT on Image(Downsampling)

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Resizing Results

Proposed upsamplingPSNR=35.28 dB, JPQM=9.65

Wavelet upsampling PSNR=35.28 dB, JPQM=9.86

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DCT upsampl ingPSNR=29.96 dB, JPQM=7.86

Bilinear upsamplingPSNR=29.74dB, JPQM=9.23

Resizing Results

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Resizing Results

Sparse data PSNR=33.97dB

Non-sparse data PSNR=35.19 dB

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Extraction of ROI

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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.

35ORGINAL IMAGE

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BINARY OF REGION OF INTEREST

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EXTRACTED IMAGE

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ORIGINAL IMAGE

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BINARY OF REGION OF INTEREST

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EXTRACTED IMAGE

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Logo insertion

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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.

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(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.

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ORIGINAL IMAGE

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LOGO TO BE INSERTED

46ORIGINAL IMAGE WITH LOGO

INSERTED

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ORIGINAL IMAGE WITH LOGO INSERTED

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IMAGE WITH LOGO INSERTED

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Thanks