Template matching is a technique used in computer vision to find sub-images in a target image that match a template image. It involves moving the template over the target image and calculating a measure of similarity at each position. This is computationally expensive. Template matching can be done at the pixel level or on higher-level features and regions. Various measures are used to quantify the similarity or dissimilarity between images during the matching process. Template matching has applications in areas like object detection but faces challenges with noise, occlusions, and variations in scale and rotation.
This presentation describes briefly about the image enhancement in spatial domain, basic gray level transformation, histogram processing, enhancement using arithmetic/ logical operation, basics of spatial filtering and local enhancements.
its very useful for students.
Sharpening process in spatial domain
Direct Manipulation of image Pixels.
The objective of Sharpening is to highlight transitions in intensity
The image blurring is accomplished by pixel averaging in a neighborhood.
Since averaging is analogous to integration.
Prepared by
M. Sahaya Pretha
Department of Computer Science and Engineering,
MS University, Tirunelveli Dist, Tamilnadu.
This presentation describes briefly about the image enhancement in spatial domain, basic gray level transformation, histogram processing, enhancement using arithmetic/ logical operation, basics of spatial filtering and local enhancements.
its very useful for students.
Sharpening process in spatial domain
Direct Manipulation of image Pixels.
The objective of Sharpening is to highlight transitions in intensity
The image blurring is accomplished by pixel averaging in a neighborhood.
Since averaging is analogous to integration.
Prepared by
M. Sahaya Pretha
Department of Computer Science and Engineering,
MS University, Tirunelveli Dist, Tamilnadu.
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This lecture is from the computer vision section of the course on udemy. Learn how to use various template matching algorithms such as squared difference, normalized square difference, correlation and correlation co-efficient for template matching. This technique can be modified for object detection and tracking.
Efficient Variable Size Template Matching Using Fast Normalized Cross Correla...Gurbinder Gill
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This is a ppt on speech recognition system or automated speech recognition system. I hope that it would be helpful for all the people searching for a presentation on this technology
This paper presents an ecient shape-based object de-
tection method based on Distance Transforms and de-
scribes its use for real-time vision on-board vehicles.
The method uses a template hierarchy to capture the
variety of object shapes; ecient hierarchies can be
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nealing). Online, matching involves a simultaneous
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over the transformation parameters. Very large speed-
up factors are typically obtained when comparing this
approach with the equivalent brute-force formulation;
we have measured gains of several orders of magni-
tudes We present experimental results on the real-time
detection of trac signs and pedestrians from a moving
vehicle. Because of the highly time sensitive nature
of these vision tasks, we also discuss some hardware-
specic implementations of the proposed method as far
as SIMD parallelism is concerned Slowly but steadily, vehicles are becoming \smarter".
Using various sensors, they can provide the driver with
relevant information about the surroundings and if de-
sired, even perform simple vehicle control tasks (e.g.
[5] [4]). The rst products are already gearing up to
the market, see for example the IR-based night vision
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An important component of more advanced on-board
vision systems is the ability to detect objects. For ex-
ample, a Trac Sign Assistant might inform the driver
Based on correlation coefficient in image matchingIJRES Journal
With the development of image technology, the application of image technology in industrial
manufacturing become more and more widely. Image matching is animportantbranch of the image processing,
and also it is very important in the process of industrial detection. The main purpose of this paper is aiming at
the traditional image correlation matching algorithm in the application of detection in industrial, which based
on similarity matching principle. This paper is going to discuss the similarity of the image matching algorithm
on the application of detection in the connector. This paper improves the algorithm to speed up the detection
velocity. In some specific circumstance, while correlation coefficient method is more simple and easy to use, the
software development cycle will be short.
Template matching is a basic method in image analysis to extract useful information from images. In this
paper, we suggest a new method for pattern matching. Our method transform the template image from two
dimensional image into one dimensional vector. Also all sub-windows (same size of template) in the
reference image will transform into one dimensional vectors. The three similarity measures SAD, SSD, and
Euclidean are used to compute the likeness between template and all sub-windows in the reference image
to find the best match. The experimental results show the superior performance of the proposed method
over the conventional methods on various template of different sizes.
TEMPLATE MATCHING TECHNIQUE FOR SEARCHING WORDS IN DOCUMENT IMAGESIJCI JOURNAL
Template matching technique is useful for searching and finding the location of a template image (Small part of image) in the larger image. This technique is also used in Optical Character Recognition (OCR) tools and these tools are used for converting the scanned document images into normal text. Template matching technique is used to find and recognize the template image which is found in the given input image. In this research work, template matching technique is applied for scanned document images which contains characters (both uppercase and lowercase) and numerals. In order to perform the comparison of the template image with the input image we have used Performance Index method and it is compared with the normalized cross correlation and cross correlation methods. Different types of comparisons done in this work are, (i) comparing single character from a word, sentence and paragraph; (ii) comparing multiple characters (words) from a word, sentence and paragraph.
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image database. To improve query result, relevance feedback is used many times in CBIR to
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Values and Match Point. Images from various types of database are first identified by using
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comparison is done w.r.t. average retrieval time. Eigen value technique found to be the best as
compared with other two techniques.
Digital image processing the statistical and structural approaches and the graph based approach for image recognition with algorithms and examples and applications where graph matching is used in pattern recognition.
Object Elimination and Reconstruction Using an Effective Inpainting MethodIOSR Journals
Abstract: Three major problems have been found in the existing algorithms of image inpainting:
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in order to generate better edges in the omitted region and to reduce the transmission of errors in the resultant
image a novel way to find optimal exemplar has been proposed. This proposal optimizes the reconstruction
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Arabic Handwritten Text Recognition and Writer IdentificationMustafa Salam
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How to Split Bills in the Odoo 17 POS ModuleCeline George
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2. 1. INTRODUCTION
Template matching is a technique in computer vision used for finding a sub-image
of a target image which matches a template image. This technique is
widely used in object detection fields such as vehicle tracking, robotics ,
medical imaging, and manufacturing .
The crucial point is to adopt an appropriate “measure” to quantify similarity
or matching. However, this method also requires extensive computational
cost since the matching process involves moving the template image to all
possible positions in a larger target image and computing a numerical index
that indicates how well the template matches the image in that position. This
problem is thus considered as an optimization problem.
A reasonable first step to approaching such a task is to define a measure or
a cost measuring the“distance”or the“similarity”between the (known)
reference patterns and the (unknown) test pattern, in order to perform the
matching operation known as template matching.
Pattern Recognition – TM Page | 2
3. 2. Template Matching Types
Template matching has been performed at the pixel level and also on higher
level.
A. Pixel Level Template Matching:
Pixel templates come in four types:
a) Total templates: Template is the same size as the input image.
There is no rotation or translation invariance.
b) Partial templates: Template is free from the background. Multiple
matches are allowed. Partial matches may also be allowed. Care
must be taken in this case -- an F template could easily match to
an E.
Template
Image
Pattern Recognition – TM Page | 3
4. c) Piece templates : Templates that match one feature of a figure.
These templates break a pattern into its component segments so,
for example, "A" can be broken down into "/", "" and "-". The
order in which templates are compared to the scene is important:
the largest templates must be tried first, since they contain the
most information and may subsume smaller templates.
d) Flexible templates: These templates can handle stretching,
misorientation and other possible deviations. A good prototype of
a known object is first obtained and represented parametrically.
Pattern Recognition – TM Page | 4
5. B. High Level Template Matching
A problem with pixel based is that although fairly cheap and simple to
implement; rotation and translation is a problem, also images are rarely
perfect suffering from blurring, stretched and other distortions and
peppered with noise.
High level template matching methods operate on an image that has
typically been segmented into regions of interest. Regions can be described
in terms of area, average intensity, rate of change of intensity, curvature and
also compared -- bigger than, adjacent to, above, distance between.
Templates are described in relationships between regions. Production rules
and other linguistic representations have been used. Also statistical methods
(relaxation based techniques) have been applied to perform the matching.
a) Feature-based Matching: When the template image has strong
features, a feature-based approach may be considered; the approach
may prove further useful if the match in the search image might be
transformed in some fashion. Since this approach does not consider
the entirety of the template image, it can be more computationally
efficient when working with source images of larger resolution.
Pattern Recognition – TM Page | 5
6. b) Template-based Matching: For templates without strong features, or
for when the bulk of the template image constitutes the matching
image, a template-based approach may be effective. Template-based
template matching may potentially require sampling of a large
number of points, it is possible to reduce the number of sampling
points by reducing the resolution of the search and template images
by the same factor and performing the operation on the resultant
downsized images (multi-resolution, or pyramid, image processing).
Image Pyramid
Image Pyramid is a series of images, each image being a result of
downsampling (scaling down, by the factor of two in this case) of the
previous element.
Pyramid Processing
At each level of the pyramid, we will need appropriately downsampled
picture of the reference template, i.e. both input image pyramid and
template image pyramid (Pyramid Processing) should be computed.
Pattern Recognition – TM Page | 6
7. Grayscale-based Matching
Although in some of the applications the orientation of the objects is
uniform and fixed (as we have seen in the plug example), it is often the
case that the objects that are to be detected appear rotated. In Template
Matching algorithms the classic pyramid search is adapted to allow multi-angle
matching, i.e. identification of rotated instances of the template.
This is achieved by computing not just one template image pyramid, but a
set of pyramids - one for each possible rotation of the template. During the
pyramid search on the input image the algorithm identifies the
pairs (template position, template orientation) rather than sole template
positions. Similarly to the original schema, on each level of the search the
algorithm verifies only those (position, orientation)pairs that scored well on
the previous level (i.e. seemed to match the template in the image of lower
resolution).
The technique of pyramid matching together with multi-angle search
constitute the Grayscale-based Template Matching method.
Pattern Recognition – TM Page | 7
8. Edge-based Matching
Edge-based Matching enhances the previously discussed Grayscale-based
Matching using one crucial observation - that the shape of any object is
defined mainly by the shape of its edges. Therefore, instead of matching
of the whole template, we could extract its edges and match only the
nearby pixels, thus avoiding some unnecessary computations. In common
applications the achieved speed-up is usually significant.
3. Template Matching Measures
Measure of match between two images is considered to be a metric that
indicate the degree of similarity or dissimilarity between them. Unless it is
specifically stated otherwise, this metric can be increasing or decreasing with
degree of similarity. Where the metric is specifically stated to be a measure
of mismatch, it is a quantity that is increasing with the degree of dissimilarity.
Pattern Recognition – TM Page | 8
9. 3.1 Measures of Match (similarity)
1) MEASURES BASED ON OPTIMAL PATH SEARCHING TECHNIQUES
Representation: Represent the template by a sequence of measurement
vectors.
Template:
Test pattern:
r(1), r(2),..., r(I )
t(1), t(2),..., t(J )
I J
Form a grid with I points (template) in horizontal and J points (test)
in vertical
Each point (i,j) of the grid measures the distance between r(i) and t(j)
Path: A path through the grid, from an initial node
(i0, j0) to a final one (if, jf), is an ordered set of nodes
(i0, j0), (i1, j1), (i2, j2) … (ik, jk) … (if, jf)
Each path is associated with a cost
K
1
k k D d( i , j )
k
0
Where K is the number of nodes across the path
Pattern Recognition – TM Page | 9
10. The optimal path (blue) is constructed by searching among all allowable
paths. The optimal node correspondence, between the test and reference
patterns, is unraveled by backtracking the optimal path.
2) Euclidean Distance
Let I be a gray level image and g be a gray-value template of size n X m.
In this formula (r,c) denotes the top left corner of template g.
3) The Edit Distance
Deals with patterns that consist of sets of ordered symbols. For example,if
these symbols are letters,then the patterns are words from a written text.
Such problems arise in automatic editing and text retrieval applications.
Other examples of symbol strings occur in structural pattern recognition.
Once the symbols of a (test) pattern have been identified, for example, via a
reading device, the task is to recognize the pattern, searching for the best
match of it against a set of reference patterns.
Pattern Recognition – TM Page | 10
11. ■ Wrongly identified symbol (e.g.,“befuty” instead of “beauty”)
■ Insertion error (e.g.,“bearuty”)
■ Deletion error (e.g.,“beuty”)
The similarity between two patterns is based on the “cost” associated with
converting one pattern to the other. If the patterns are of the same length,
then the cost is directly related to the number of symbols that have to be
changed in one of them so that the other pattern results.
The Edit distance between two string patterns A and B, denoted D(A, B), is
defined as the minimum total number of changes C, insertions I ,and
deletions R required to change pattern A into pattern B,
D(A,B) min[C( j) I ( j)
R( j)]
j
Where j runs over all possible variations of symbols, in order to convert A
B.
Computation of the Edit distance with (a) an insertion, (b) a change, (c) a
deletion, and (d) an equality.
Pattern Recognition – TM Page | 11
12. Allowable predecessors and costs
1. Diagonal transitions:
t i r j
0, if ( ) ( )
t i r j
1, ( )
( )
d i j i j
( , 1, 1)
2. Horizontal and vertical transitions:
d(i, j i 1, j) 1
d(i, j i, j 1) 1
4) MEASURES BASED ON CORRELATIONS
The major task here is to find whether a specific known reference pattern
resides within a given block of data. Such problems arise in problems such as
target detection, robot vision, video coding. There are two basic steps in
such a procedure:
Step 1: Move the reference pattern to all possible positions within the
block of data. For each position, compute the “similarity” between the
reference pattern and the respective part of the block of data.
Pattern Recognition – TM Page | 12
13. Step 2: Compute the best matching value.
N
i i
x x y y
( )
1
1
N
i
2 2
1
0
N
x x y
y
i i
0
0
i
i
cor
x
x y y x is the template gray level image
2 2
i
i Pattern Recognition – TM Page | 13
1
0
1
0
1
0
) (
N
i
N
i
i
N
i i
y y x x
is the average grey level in the template image
y is the source image section
y is the average grey level in the source image
N is the number of pixels in the section image
(N= template image size = columns * rows)
The value cor is between –1 and +1,
with larger values representing a stronger relationship between the two images.
14. 3.2 Measures of Mismatch (dissimilarity)
These measures of match are based on the pixel-by-pixel intensity
differences between the two images f and g.
1) Root mean square distance (RMS): The RMS distance metric is a
common measure of mismatch between two digital images. It is given
by:
2) Sum of absolute differences (SAD): compare the intensities of the
pixels to handle translation problems on images, using template
matching.
A pixel in the search image with coordinates (xs, ys) has intensity Is(xs, ys) and
a pixel in the template with coordinates (xt, yt) has intensity It(xt, yt ). Thus
the absolute difference in the pixel intensities is defined as
Diff(xs, ys, x t, y t) = | Is(xs, ys) – It(x t, y t) |.
Pattern Recognition – TM Page | 14
15. 4. Problems with template matching
1) The template represents the object as we expect to find it in the image
2) The object can indeed be scaled or rotated
3) This technique requires a separate template for each scale and
orientation
4) Template matching become thus too expensive, especially for large
templates
5) Sensitive to:
–noise
–occlusions
Pattern Recognition – TM Page | 15
16. 5. Template Matching Applications:
1) Template matching with various average face pyramid levels.
2) 3D reconstruction.
3) Motion detection.
4) Object recognition.
5) Panorama reconstruction.
Pattern Recognition – TM Page | 16
17. Reference:
1. G.s.cox,1995. “ template matching and measures of match in image
processing”,July 12 . cape town university.
2. https://www.adaptivevision.com/pl/dane_techniczne/dokumentacja
/3.2/machine_vision_guide/TemplateMatching.html
3. http://numerics.mathdotnet.com/docs/Distance.html
4. http://www-cs-students.
stanford.edu/~pdoyle/quail/notes/pdoyle/vision.html#Te
mplate Matching
5. http://en.wikipedia.org/wiki/Template_matching
6. http://www.lira.dist.unige.it/teaching/SINA/slides-current/interest-points.
pdf
7. OpenCV 2.4.5.0 documentation.htm
8. Jain. D, Tolga. H, and Meiyappan. S, “Face Detection using Template
Matching”, , EE 368 – Digital Image Processing, Spring 2002-2003.
Pattern Recognition – TM Page | 17