IRJET-Hardware Co-Simulation of Classical Edge Detection Algorithms using Xilinx System Generator

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 01 | Jan-2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 912
Hardware Co-Simulation of Classical Edge Detection Algorithms
Using Xilinx System Generator
Avinash G. Mahalle1, A. M. Shah2
1M.Tech, Dept. of Electronics Engineering, GCOEA, Maharashtra, India
2Assistant Professor, Dept. of Electronics Engineering, GCOEA, Maharashtra, India
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Abstract - Edge Detection is one of the most important and
fundamental processes in the field of Image Processing and
Computer Vision. It is a process of localizing pixel intensity
changes. Classical edge detection methods such as Robert,
Prewitt and Sobel are simple to design than Laplacian based
methods. Hence, these are used in Real Time image processing
applications quiet more often. The proposed designs for
Classical Operators utilize minimum resources. At the same
time, it also enhances maximum frequency of operation.
Spartan-3E Starter Kit is used for prototyping purpose. JTAG
Hardware Co-Simulation utilizes hardware in loop approach.
An efficient way to implement image processing tools on
reconfigurable hardware is to design algorithms using Xilinx
System Generator.
Key Words: Image Processing; Edge Detection; Xilinx
System Generator; JTAG Hardware Co-simulation;
Spartan-3E FPGA
1. INTRODUCTION
Digital Image consists of various pixels. Very few of these
pixels actually carry information. By detecting edges in an
image, one can preserve useful structural information and
eliminate redundant data [1]. It is an efficient way for
storage and bandwidth utilization. Edges can be
characterized by sudden change in the pixel intensity. Thus,
edges are components with high spatial frequencies. Any
change can be located by mathematical tool named as
derivative. In discrete domain, derivative is nothing but
difference equations. By convolving image pixels with given
masks this change can be located. Finding gradient implies
taking derivative for one time whereas, for findingLaplacian
derivative is taken two times. Edge profile can be
categorized as step, ramp, ridge and roof. Gradient based
methods find out maximum/minimum values whereas,
Laplacian based methodsfind out zero crossing[2].Gradient
works well when image contains sharp intensity and low
noise. Hardware implementation of these edge detection
algorithms is essential in order to use it in real time[3].Field
Programmable Gate Array (FPGA) has advantages over
Application Specific Integrated Circuit (ASIC) with no non-
recurring expense (NRE), less time to market and high
flexibility. A low cost Spartan-3E Starter Kit is used as a
hardware platform for implementation. In hardware co-
simulation approach normal Simulink blocksareexecutedin
MATLAB environment that generates desired operation
while JTAG simulation block loads bit stream file generated
(*.bit) in FPGA using Hardware in loop [4]. Writing code in
Hardware Description Languages (HDL) along with its test
bench programming is very tedious job. Xilinx System
Generator provides an efficient way to program FPGA by
designing algorithm using blocks [5]. Using various
compilation, HDL code and required Test bench are
generated automatically along with variousparameterssuch
asminimum period, maximum frequency, powerdissipation
and resource utilization [6].
2. EDGE DETECTION ALGORITHMS
Edge Detection algorithms are broadly classified as follow:
-First Order Derivative Methods [Gradient Based]
 Robert Operator
 Prewitt Operator Classical Operators
 Sobel Operator
-Second Order Derivative Methods [Laplacian Based]
 Marr-Hildreth Edge Detector [LoG]
-Optimal Edge Detectors: Canny Algorithm
Classical operators include Robert, Prewitt and Sobel
operators. Main advantage of these operatorsis that theyare
simple to design and have very low latency. These are also
less susceptible to noise than Laplacian based methods.
Gradient can be find out by convolving operator mask with
image pixels. Masks are of different dimensions.
Fig -1: Horizontal & Vertical Masks for Classical Operators
Robert operator is having [2×2] mask whereas, Prewitt and
Sobel have[3×3]mask. TheFig-1 showsboth horizontal and
vertical masks for all classical operators.

3. SYSTEM DEVELOPMENT & PROPOSED DESIGNS
3.1 System Requirement
Xilinx System Generator (XSG) provides a common
environment for MATLAB/Simulink and ISE DesignSuit.XSG
is invoked by configuring MATLAB R2011b with ISE Design
Suit 14.4. Any image processing application can be
implemented inXSGusing three basic steps. These are image
pre-processing, system generator blocks and image post
processing. Gateway In and Gateway Out act as a connector
between Simulink blocks and System Generator blocks.
Various types of compilation can be achieved using system
generator token [8].
Hardware co-simulation compilation is used to observe
Software and Hardware output images simultaneously
whereas Timing & Power Analysis compilation provides
information related many parameters such as resources
utilized, minimum period, maximum frequency of operation
and power. Following steps give system generator flow-
 Configure ISE Design Suit with MATLAB/Simulink
 Design required algorithm using Simulink blocks
 Compile, simulate design to check its correctness
 Choose hardware co-simulation compilation
 Generate JTAG h/w co-simulation model
 Observe waveform, RTL diagram & HDL code
 Program FPGA with bit stream (*.bit) file
 Compile design to performTiming &PowerAnalysis
3.2 Proposed Classical Operators Design
Theonly difference while designing alltheclassicaloperators
is their gradient filters. Depending on the masks, horizontal
and vertical filters are designed.
Fig -2: Proposed design for Classical Operators
Fig- 2 shows complete design for all the classical operators.
The complete edge detection algorithm is designed in Edge
Detection Algorithm block which is connected in between
Gateway blocks. It consists of horizontal and vertical
gradient filters followed by thresholdingblock.Thresholding
block can be design as shown in Fig- 3. It uses Mux,
Relational Comparator and Constant blocks. When gradient
magnitude exceedsgiven threshold, it is considered asEdge.
Image from file block inputs color/gray image and Video
viewer block displays output binary image. JTAG Co-
simulation block is logically equivalent to Gateway andEdge
Detection Algorithm blocks. Using JTAG cable the design is
implemented on the FPGA hardware.
Fig -3: Design for Thresholding Block
3.3 Designs for Gradient Filters
Based on corresponding masks of Classical operators
gradient filters are designed. These gradient filters mainly
calculate gradient along horizontal and vertical directions.
But in case of Robert operatorgradient calculation is done in
diagonal direction. Filters are designed using various basic
Xilinx blocks such as AddSub, Register, Virtex2 Line Buffer
etc. Fig-4 and 5 indicate Robert Diagonal Gradient Filters.
Fig -4: Horizontal Gradient Filter for Robert Operator
Fig -5: Vertical Gradient Filter for Robert Operator
As the size of mask decreases, it becomes more susceptible
to noise. Thus, out of all classical operators Robert is more
sensitive to noise. Prewitt operator on the other hand uses
3×3 mask. Fig- 6 and 7 indicate horizontal and vertical
gradient filter designs for Prewitt Operator.

Fig -6: Horizontal Gradient Filter for Prewitt Operator
Fig -7: Vertical Gradient Filter for Prewitt Operator
Sobel operator also uses 3×3 mask in order to find out
gradientmagnitude. The onlydifferencebetweenPrewittand
Sobel is in later one, more weightage has been given to the
Central pixel in order to locate maximum edges. In proposed
design shift block is used for multiplication purpose. Shifting
a bit oneplace to the left is logically equivalenttomultiplying
it by two. Fig- 8 and 9 indicate Horizontal and Vertical
Gradient Filters for Sobel Operator.
Fig -8: Horizontal Gradient Filter for Sobel Operator
Fig -9: Vertical Gradient Filter for Sobel Operator
4. RESULTS AND PERFORMANCE ANALYSIS
4.1 Results for Edge Detection Techniques
The complete design is logically equivalent to JTAG Co-
Simulationmodel. Preprocessing and post-processingblocks
are designed Simulink blocks. Results are observed in
MATLAB/Simulink environment whereas, performance
parameters are observed with the help of timing & power
analysis compilation. Fig- 10 shows results for all classical
edge detection algorithmson256×256standardCoinsimage.
From the analysis we can say that out of classical operators
Sobel provides maximum edges followed by Prewitt and
Robert. Thus, generally Sobelis used for gradientcalculation
in Canny algorithm as well.
Fig -10: Results for 256×256 coins gray image
Table - 1 provides detailed resource utilization for all the
Classical Edge Detection Algorithms and Table - 2 provides
various Timing & Power parameters for 256×256 input
image using inbuilt Tools [7].

Table -1: Resources Utilization for 256×256 image
LOGIC UTILIZATION ROBERT PREWITT SOBEL
No. of slice flip flops 64 150 148
No. of 4 input LUTs 70 163 159
No. of occupied slices 65 152 167
Total no. of 4 i/p LUTs 87 189 186
No. used as a logic 70 163 159
No. used as a route-thru 17 26 27
Table -2: Timing and Power analysis for 256×256 image
Technique
Total Power
(Watts)
Min. Period
(ns)
Max. Frequency
(MHz)
Robert 0.116 4.48 223.36
Prewitt 0.126 5.11 195.58
Sobel 0.127 5.01 199.60
4.2 Comparative Analysis for Classical Operators
Classical operators such as Robert, Prewitt, Sobel are
designed for512×512 LenaColorImage.Fig-11showsresults
for all classical operators. Utilized resources are compared
with the design given in literature. Both designs use same
hardware platform i.e., Spartan-3E Starter Kit [9]. Table-3
provides resources utilized by proposed design whereas
Table -4 provides resources utilized by design in [7].
Fig -11: Results for 512×512 Lena color image
Table -3: Proposed design for 512×512 image
Technique Slices FFs LUTs IOBs
Robert 71 66 91 17
Prewitt 151 152 191 17
Sobel 167 152 188 17
Table -4: Design in [7] for 512×512 image
Technique Slices FFs LUTs IOBs
Robert 768 1237 1209 32
Prewitt 943 1357 1479 32
Sobel 945 1357 1604 32
From Tables-3 and 4, it is inferred that proposed design
utilizes much less resources than that of design in [7]. To get
better comparative view a graphical representation of both
the designs is shown in Fig- 12. Parameters used in the
comparison are occupied Slices, FFs and LUTs.
0
200
400
600
800
1000
1200
1400
1600
1800
Slices FFs LUTs
Proposed Robert
Robert in [7]
Proposed Prewitt
Prewitt in [7]
Prposed Sobel
Sobel in [7]
Fig -12: Comparative Analysis for Proposed Design and
Design in [7]
5. CONCLUSIONS
Themainobjective of thispaperwastodesign Classical Edge
Detection algorithmswhich use minimumresourcesinorder
to maximize Frequency of operations. Designed Classical
operators are more efficient in terms of resource utilization
than previous work. These operators are implemented on
Spartan-3E FPGA by utilizing hardware co-simulation
compilation using XSG. Further, proposed work can be
followed to make Canny algorithm design simpler than
conventional one.
REFERENCES
[1] R. C. Gonzalez, R. E. Woods, Digital Image Processing,
3rd edition, Prentice Hall, pp.187-190, 2007
[2] R. Maini, H. Aggarwal. “Study and comparison ofvarious
image edge detection techniques,” InternationalJournal
of Image Processing. Vol.3, pp.1-12, Feb 2009
[3] Y. Said, T. Saidani, F. Smach and M. Atri, “Real Time
Hardware Cosimulation of Edge Detection for Video
Processing System,” IEEE, pp.852-857, 2012
[4] Kiran M., K. M. War, L. M. Kuan, L. K. Meng, L. W. Kin,
“Implementing image processing algorithms using
‘Hardware in the loop’ approach for Xilinx FPGA,”
Proceedings of the International Conference on

Electronic Design, Dec. 1-3, IEEE Xplore Press, Penang,
pp.1-6, 2008
[5] M. Ownby, W. H. Mahmoud, “A design methodology for
implementing DSP with Xilinx System Generator for
Matlab,” IEEE International Symposium on System
Theory, pp.404-408, March 2002
[6] Avinash G. Mahalle, A. M. Shah, “FPGAImplementationof
Gradient Based Edge Detection Algorithms,”
International Journal of Innovative Research in
Computer and Communication Engineering (IJIRCCE),
Volume 5, Issue 5, May 2017
[7] G. B. Reddy, K. Anusudha, “Implementation of image
edge detection on FPGA using XSG,” International
Conference on Circuit, Power and Computing
Technologies (ICCPCT), pp.1-5, 2016
[8] Xilinx System Generator Users Guide, www.xilinx.com
[9] Spartan-3E Starter Kit Users Guide, www.xilinx.com
BIOGRAPHIES:
Avinash G. Mahalle received B.Tech.
Degree in Electronics and
Telecommunication from Shri Guru
Gobind Singhji Institute of Engineering
and Technology, Nanded in 2014 and
M.Tech. Degree in Electronics System &
Communication from Government
College of Engineering, Amravatiin2017.
His research interests are VLSI design,
Image Processing etc.
A. M. Shah received the B.E. degree in
Electronicsand Telecommunicationfrom
SGB University, Amravati in 2004 andthe
M. Tech. degree in Electronics (VLSI)
from RTM University, Nagpur in 2008.He
is working as Assistant Professor,
Electronics Engineering Department,
Government College of Engineering
Amravati.

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