Block Truncation Coding

SIR ISSAC NEWTON ARTS & SCIENCE COLLEGE
NAGAPATTINAM, TAMILNADU
R.Maragatham-P15274356
K.Priya-P15274357
II M.SC(ComputerScience)

Submitted to:
B.SOWBARNIKA M.Sc.,M.Phil.,
Assistant professor
Department of Computer Science
.

 Introduction
 Block Truncation Coding
 BTC Algorithm
 Advantages of BTC
 Drawbacks of BTC
 Variants of BTC
 Absolute Moment BTC
 Adaptive BTC
 Conclusion

INTRODUCTION :
 The BTC algorithm is a simple, block-based, spatial-
domain.
 Image compression technique developed by Delp and
Mitchell.
 The amount of image data grows day by day. Large storage
and bandwidth are needed to store and transmit the images,
which is quite costly.
BTC is a recent technique used for compression of
monochrome image data.
The truncated block of the BTC is the one-bit output of the
quantizer for every pixel in the block.

Block Truncation Coding:
Block Truncation Coding, or BTC, is a type of lossy image
compression technique for greyscale images.
Block truncation coding (BTC) has been considered a highly
efficient compression technique for decades.
It’s inherent artifacts, blocking effect and false contour, caused by
low bit rate configuration are the key problems.

BTC Algorithm:
 Step 1: Divide the image into small non-
overlapping blocks of size 4 x 4 pixels.
 Step 2: Compute the statistical moments x and σ
of the block using the equations 1, 2 and 3.
 Step 3: Generate the bit-plane with 0’s and 1’s.
 Step 4: Transmit or store the bit-plane, x and σ.
 Step 5: Repeat the steps 2 through 4 for all the blocks
of the input image.

Advantages of BTC:
 Small complexity(faster than TC).
 Each block can be compressed separately according to
its variance.
 Requires little extra memory
 Low computational complexity
 Fixed and Adaptive bit-allocatin optional
 Preserving edges
 Easy to implement

Disadvantages of BTC:
 High bit-rate when compared to techniques such as
DCT, VQ, etc…
 Blocky appearance in the reconstructed image in
some cases.
 Ragged edges
 The BTC method described above can be extended to
color images by applying.

Variants of BTC:
 BTC has been used in image and video compression.
 In this study BTC was compared with the DCT and
hybrid coding techniques in the context of high
resolution aerial.
 This study showed that at data rates from 1-3 bits/pixel
(monochrome images).
 These include coding graphics images, predictive
coding , coding color images, the use of absolute
moments, video and hardware implementations.

Absolute Moment BTC:
 Absolute Moment Block Truncation Coding (AMBTC)
by [Lema M.D. and Mitchel O.R., 1984]
 It preserves x and the sample first absolute central
moment.
 Also the coding and decoding processes are very fast
because the square root multiplication operations are
omitted.
 The bit rate remains same as that of BTC.

Adaptive BTC:
 In Adaptive Block Truncation Coding(ABTC)
 The number of bits required to preserve high dynamic
range&resolution in a typical picture range.
 The input image blocks are categorized into
three types namely:
 low-activity blocks,
 medium-activity blocks,
 high-activity blocks.
 A four-level quantizer is designed with quantizers
being xmin,(2xmin+xmax)/3,(xmin+2xmax)/3,xmax.
Many efficient image coding schemes have evolved.

CONCLUSION:
 Block Truncation Coding has come a long way since
March 1977.
 Despite the recent work image video compression
standards
 BTC is still attractive in many applications that
require low complexity and moderate data rates.
 These include Internet video with software-only code,
digital cameras and printers.

P.MEERABAI M.C.A.,M.Phil.,
HEAD OF THE DEPARTMENT
COMPUTER SCIENCE

Block Truncation Coding

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