# How To Convolve An Image In Matlab

Today's blog post was written by Spandan Tiwari, a developer on the Image Processing Toolbox team. The pixels of an image is distributed in 2D spatial domain. What is image filtering? Modify the pixels in an image based on some function of a local neighborhood of the pixels. The purpose of this page is not to describe how convolution works (that is done elsewhere), but to show how to install and use ConvolveGUI. How convolution can be done in two dimensions? Can you show me an example and explanation of the 2D convolution? How can two dimensional convolution be done in MATLAB? In a previous post the basics of convolution was already discussed with some examples. Assuming the question is with regard to Discrete time signals the procedure is as follows: * Append the cyclic suffix i. For instance, regardless of image size, tiling regions of size 5 x 5, each with the same shared weights, requires only 25 learnable parameters. You create a function that keeps calling itself until a condition is satisfied, and then the function delivers an answer based on the results of all those calls. Replace each pixel by a linear combination of its neighbors. Doing by hand. How to Run This Project ? Open laplacian. Sharpening Image in matlab using Convolution Matrix. This Matlab code package implements the image interpolation algorithm based on the directional cubic convolution interpolation which has been described in the following paper: D. fr August 10, 2004 First keep in mind that this is not a Matlab tutorial. The convolution operator is often seen in signal processing, where it models the effect of a linear time-invariant system on a signal. Learn more about convolution. Xilinx is a package. I know how to create the filter using [b,a]=butter(order, cutoff), but then what? What I would normally do is convolve my filter with my data but I cant convolve [b,a] with the image data. The design of the architecture according to th. It was aimed at human beings to improve the visual effect of people. The algorithm we use is the Sparse Bayesian regression algorithm of Tipping and Faul. I have tried normalizing and then convoluting but that did not work. I have to do some other filters as well, on different images, but I imagine it will be similar for each type. It is done in this way. Convolution in Matlab The convolution in matlab is accomplished by using "conv" command. On the right side of the applet we extend these ideas to two-dimensional discrete functions, in particular ordinary photographic images. Here is a simple example of convolution of 3x3 input signal and impulse response (kernel) in 2D spatial. how to perform fast convolution small patches in matlab Tag: matlab , image-processing , matrix , convolution I have a large number of 2D image patches and a set of 2D filters. Matlab has extensive help files available online. One class of image digital filters is described by a rectangular matrix of real coefficients called kernel convoluted in a sliding window of image pixels. This is related to a form of mathematical convolution. e; copy the first few samples of the signal and append them to the signal. While this can be done in terms of a cross correlation, care has to be taken to normalize both input and template, as cross correlation by itself is not invariant to mean shifts. To simplify and reduce ifs, you should pad the image with zeros before starting your convolution loop. Convolution • g*h is a function of time, and g*h = h*g – The convolution is one member of a transform pair • The Fourier transform of the convolution is the product of the two Fourier transforms! – This is the Convolution Theorem g∗h↔G(f)H(f). Convolution mathematical operation knowledge. Demonstrate the necessary components of the code used to perform convolution in Matlab in a simplified manner. The pixels of an image is distributed in 2D spatial domain. While I understand that the OTF (optical transfer function) is represented by the image I am getting, how am I superposed to deconvolve the image I have using the very same image? Here is an example of the image I am trying to deconvolve: I have a program which automatically singles in on the bead and crops the rest of the image. Convolution in time domain corresponds to multiplication in frequency. Convolution is a mathematical way of combining two signals to form a third signal. so that I am asking for your help. However, this can often be sped up significantly if we use the Convolution Theorem , which states in essence that conv (a,b) = ifft ( fft (a,N). In this tutorial, I loaded a color image in Matlab then converted it in grays-scale image. 2D Convolution Matrix in Matlab. Addition takes two numbers and produces a third number, while convolution takes two signals and produces a third signal. Other padding techniques include replicate padding, periodic extension, mirroring, etc. Convolution Mask. I have been using 3x3 convolution masks like , but the results are not that satisfactory. Learn more about signal system. Image Local Polynomial Approximation and its applications. This paper discusses a method on developing a MATLAB-based Convolutional Neural Network (CNN) face recognition system with Graphical User Interface (GUI) as the user input. The toolbox supports a wide range of image processing operations, including: – Geometric operations – Neighborhood and block operations. Convolution of Signals in MATLAB Robert Francis August 29, 2011. Convolution will enlarge an image but it filters the image and you haven't said that you want to blur or sharpen the image. To simplify and reduce ifs, you should pad the image with zeros before starting your convolution loop. I will follow a practical verification based on experiments. com/ You will need: 1. Matlab and Image Detection. Part 2: Convolution and Cross-Correlation - G. Convolution is implemented in the Wolfram Language as Convolve[f, g, x, y] and DiscreteConvolve[f, g, n, m]. First we should flip the kernel, then slide the kernel on the input signal. *fft2(picture)), but at first, matrix "h" and "picture" must be extend to the same size. If we multiply a Continuous-Time signal f(t) by a periodic pulse sequence we can get a sampled version of our signal. Load the MATLAB demo image rice3 with img = imread(’rice. The images used in this example are both MATLAB example images. I want to calculate the convolution sum of the continuous unit pulse with itself, but I don't know how I can define this function $$\delta(t) = \begin{cases} 1, 0 \le t \lt 1 \\ 0, otherwise \end{cases}$$ in Matlab. Discrete convolution. MATLAB for Absolute Beginners MATLAB is much easier to learn when you can try everything for yourself in this course for beginners! With more than a million users, MATLAB is a must know programming language for science, engineering, and economics professionals. Learn more about image processing Image Processing Toolbox MATLAB Answers. i have to import the data from excel. xl(t) yl(t). The goal of this lab is to learn how to implement FIR filters in Matlab, and then study the response of FIR filters to various signals, including images or speech. So to avoid this problem adjust the length of x and h to be equivalent to the final length as shown:-. The processing include blurring an image, sharpening an image e. This section of MATLAB source code covers convolution matlab code. It is the single most important technique in Digital Signal Processing. I know how to create the filter using [b,a]=butter(order, cutoff), but then what? What I would normally do is convolve my filter with my data but I cant convolve [b,a] with the image data. is a Toeplitz matrix. m on your Matlab , i'm using Matlab 2015b; Run it, input your image and Kernel; Done. A perfect example of 2D signal is image. Title: Convolution in Matlab 1 Convolution in Matlab. I'm trying to erode an image in MATLAB without using the "imerode" function. sara: Naz suggested that you'd want to convolve the signal with itself. txt) or read online for free. gpuArrayA — Image to be filtered gpuArray object. Convolution will assist us in solving integral equations. Instructions. Although MATLAB contains a pre-built convolution function, it is possible to calculate the discrete convolution integral yourself. Sharpening Image in matlab using Convolution Matrix. An example H1 for 100x100 image is with a cutoff of 20 is a variable H1 inside a data. Theorem 12. Convolution is a mathematical operation that blends two functions relative to the overlap of one function as it is shifted over another. One way is to just convolve with a kernel that has all positive weights, like a box filter: boxKernel = ones(21,21); % Or whatever size window you want. Hello, Sir, I would like to develop a matlab code for edge enhancement of an image without using any matlab pre defined functions for edge enhancement like 'canny','sobel' etc. Shen, and W. University of Washington Applications of Convolution in Image Processing with MATLAB Author: Instructor: Sung Kim Riley Casper August 20, 2013 1 Abstract The article presents a short introduction to image processing and image filtering techniques. Convolution definition is - a form or shape that is folded in curved or tortuous windings. Algorithm: Load an RGB image Get the size(mxn) of the image Create a new matrix of zeros of size mxn Read the values of R,G,B in each pixel while traversing through every pixels of the image Restore pixels with required color to 1 and rest to 0 to the newly created matrix Display the newly created matrix and the resultant image would be the. There is no explicit index referrence in the algorithm. So to avoid this problem adjust the length of x and h to be equivalent to the final length as shown:-. Summary This article aims at explaining the graphical method of 2-D convolution and the concept of zero padding with respect to digital image processing. Not the solution you were looking for? IT issues often require a personalized solution. Convolution in time domain corresponds to multiplication in frequency. If your shorther pulse signal is really a rectengular waveform then please look for the other answer, but otherwise for a general waveform pulse the following code snipped (excerpted from Maximillian's previous post) shows the actual results (on my laptop with MATLAB R2015) of timings for a frequency domain vs time domain implementation of the convolution operation in simplest terms. 2 or higher. 2 Convolving Images Now it's your turn to play with image convolution. Just plain for, this is because im trying to use a code that can also be implemented on C. Computing the inverse of the convolution operation is known as deconvolution. Yes Sir i have to convolve with greyscale image of F and image Aplease tell me how to do this. So far I have this. Instructions. sara: Naz suggested that you'd want to convolve the signal with itself. When used with a gpuArray, imfilter computes gpuarrayB , using either single- or double-precision floating point, depending on the data type of gpuArrayA. Subtract from the original. For more pretrained networks in MATLAB ® , see Pretrained Deep Neural Networks. The computational advantage of separable convolution versus nonseparable convolution is therefore: For a 9-by-9 filter kernel, that's a theoretical speed-up of 4. i don't want to do any auto-correlation. How do I plot this convolution correctly???. In convolution, before elements of two vectors are multiplied one is flipped and then shifted. Learn more about signal processing. In this tutorial the simplest 1D convolution is to be explained, but of course this operation works for higher dimensions as well. Allocate space for output image. , Someday I might be able to memorise the whole Matlab documentation. Basic; Tutorial Contents. That is, it will be the same as circular convolution, modulo the length of the vectors. Discover what MATLAB. It has applications that include probability, statistics, computer vision, natural language processing, image and signal processing, engineering, and differential equations. Basic image processing with matlab code. Choose a web site to get translated content where available and see local events and offers. MATLAB version 9 or above. MATLAB is a data analysis and visualisation tool designed to make matrix manipulation as simple as possible. That means there are multiple 2D planes which makes the convolution operation complex. Specifically, we can take the learned 8x8 features and ”‘convolve”’ them with the larger image, thus obtaining a different feature activation value at each location in the image. Since the input image is represented as a set of discrete pixels, we have to find a discrete convolution kernel that can approximate the second derivatives in the definition of the Laplacian. %CONVOLUTION IN MATLAB. 2D convolutions are used as image filters, and when you would like to find a specific patch on an image. Although there are a lot of image processing applications out there, developing your own can be very worthwhile to have custom functionality. pptx - Free download as Powerpoint Presentation (. Without padding the result will be equivalent to circular convolution as you point out. Here is the code and the image I used. On the image there are three objects: a jumping man, the blue sky and the white snow. You don't need to turn anything in, just read through this document and run the code that is provided. Implementing convolution. And it would work for color images, for instance by working on different color places. conv2() for gray images. Matlab and Image Detection. Option valid returns those elements only which were fully covered, so there was no sliding off during the windowing. I am using image filtering for an image processing algorithm I'm developing. For instance, regardless of image size, tiling regions of size 5 x 5, each with the same shared weights, requires only 25 learnable parameters. How do you watermark an image in MATLAB? A sigital Watermarking example in Matlab is in related links. Scribd is the world's largest social reading and publishing site. In simple terms the convolution layer, will apply the convolution operator on all images on the input tensor, and also transform the input depth to match the number of filters. Computing the inverse of the convolution operation is known as deconvolution. Here is a simple example of convolution of 3x3 input signal and impulse response (kernel) in 2D spatial. This can be useful for filtering, or smoothing, noisy data. First, that means that the first element of an image is indicated by 1 (not 0, as in Java, say). The convolution extracts the horizontal edges of the pedestal. Demonstrate the necessary components of the code used to perform convolution in Matlab in a simplified manner. The operator moves over the image to affect all the pixels in the image. Presently I want to implement in Matlab gabor filters and image covolution with Image. 2 or higher. (the Matlab script, Convolution. but i fft2 the mask with the dimensions of the image and then convolve with the fft2 of the image. Learn more about signal system. For more pretrained networks in MATLAB ® , see Pretrained Deep Neural Networks. Compute the full convolution of A and B, which is a 6-by-6 matrix. results in an image where edges are accentuated; this is known as a sharpening operation, which is kind of like the opposite of blurring. To avoid edge effects, you may skip a strip of width r around the edge of the image. Lathi, Linear Systems and Signals. This and many other kernels are built into image editing software such as Photoshop. http://mariamghazaly. ConvMtxSV: MATLAB implementation for constructing spatially variant convolution matrices This software is a MATLAB implementation of the following paper: S. When gpuArrayA contains double-precision or uint32 values,. Procedure: Blur the image. I'm currently attempting to convolve two exponential(one gaussian) functions in order to create a convolved equation in Matlab that I can then use in the custom equation section of the Curve Fitting application to fit to a distribution in order to extract certain parameter values for multiple datasets. One class of image digital filters is described by a rectangular matrix of real coefficients called kernel convoluted in a sliding window of image pixels. Create a 3-by-3 random matrix A and a 4-by-4 random matrix B. Learn more about signal system. Aliasing and image resizing - part 3 4 Posted by Steve Eddins , January 16, 2017 Today I'll try to wrap up my discussion about how aliasing affects image resizing and about how the imresize function tries to prevent it. Convolution in time domain corresponds to multiplication in frequency. The function supports both 2D and 3D images. I have to do some other filters as well, on different images, but I imagine it will be similar for each type. Convolution. If u is a vector with length n and v is a vector with length m, then their convolution will be of length nm-1 ; Convolution is a commutative operation. Because color image has multiple channels. You create a function that keeps calling itself until a condition is satisfied, and then the function delivers an answer based on the results of all those calls. Students can often evaluate the convolution integral (continuous time case), convolution sum (discrete-time case), or perform graphical convolution but may not have a good grasp of what is happening. Not the solution you were looking for? IT issues often require a personalized solution. Convolution will enlarge an image but it filters the image and you haven't said that you want to blur or sharpen the image. Learn more about convolution I am still pretty new to MatLab and am still learning the ropes. Below is how your function could be used. While I understand that the OTF (optical transfer function) is represented by the image I am getting, how am I superposed to deconvolve the image I have using the very same image? Here is an example of the image I am trying to deconvolve: I have a program which automatically singles in on the bead and crops the rest of the image. Template Matching by Convolution. I am trying to load 2 different images and convolve them together into 1 image in matlab. ECE 352, Lab 1 – MATLAB, usb_cam, Convolution are the Red, Green and Blue separated out into individual images, Figure2. 2D convolutions are used as image filters, and when you would like to find a specific patch on an image. Common image processing include image enhancement, restoration, encoding, and compression. Make the routine as efficient as possible: Restrict usage of for loops which are expensive (use matrix multiplications and matlab routines such as dot etc). Since many. The MATLAB function imfilter performs convolution on the input image. Syntax of this builtin convolution command is v=conv(x,h) where x and h are the input functions while v is our output. MATLAB image processing codes with examples, explanations and flow charts. Image to be filtered, specified as a gpuArray object. The video explains how 2D convolution works on MATLAB and how it can be used to edit and play with images. As you have already seen, based on the property that multiplying the FFT of two functions from the spatial domain produces the convolution of those functions, you can use Fourier transforms as a fast convolution on large images. Follow the steps to generate signal y(t). Create a 3-by-3 random matrix A and a 4-by-4 random matrix B. Due to use of SSE (SIMD Vectorization) the image number of columns. Convolution in time domain corresponds to multiplication in frequency. Hello Matlab Experts, I'm currently delving into the world of image processing and convolution. Previously, I showed how to whiten a matrix in Matlab. It can be used for several tasks, for example signal or image processing. but what you are doing is correlation not convolution. I'm not very familiar with Matlab or similar programs so bear with me. When filtering an image, each pixel is affected by its neighbors, and the net effect of filtering is moving information around the image. I have four columns of data with x and y values of two signals. in both process (space domain and frequency doamin) the output should be same. We have explained about how to change size of image. Create a 3-by-3 random matrix A and a 4-by-4 random matrix B. Choose a web site to get translated content where available and see local events and offers. What is the Image Processing Toolbox? • The Image Processing Toolbox is a collection of functions that extend the capabilities of the MATLAB's numeric computing environment. Syntax of this builtin convolution command is v=conv(x,h) where x and h are the input functions while v is our output. Since many. How to convolve a sphere with a shere in 3D and Learn more about shapes, geometry, spheres, 3d, convolution, challenge MATLAB, Image Processing Toolbox, Computer Vision Toolbox. The Iterative Deconvolution 3D plugin uses a PSF image z-stack to correct the image contrast vs. I am trying to load 2 different images and convolve them together into 1 image in matlab. Convolution Filter. You create a function that keeps calling itself until a condition is satisfied, and then the function delivers an answer based on the results of all those calls. txt) or view presentation slides online. Convolve the rows of A with the vector u, and then convolve the rows of the result with the vector v. Download MATLAB code: optics5. This is just a list of. sara: Naz suggested that you'd want to convolve the signal with itself. How to convolve two equations. Is a matrix applied to an image and a mathematical operation comprised of integers It works by determining the value of a central pixel by adding the. Convolution • g*h is a function of time, and g*h = h*g – The convolution is one member of a transform pair • The Fourier transform of the convolution is the product of the two Fourier transforms! – This is the Convolution Theorem g∗h↔G(f)H(f). when applied to images, known collectively as image processing, and will introduce the concepts of convolution as a means to apply DSP techniques and simplify cal-culations. In fact they work in almost the exactly the same way, matching up a neighbourhood 'kernel' at each location, making them a just another special 'method' of morphology. Image to be filtered, specified as a gpuArray object. The video explains how 2D convolution works on MATLAB and how it can be used to edit and play with images. Valeska Pearson (view profile) % Read in a standard MATLAB color demo image. This Matlab code package implements the image interpolation algorithm based on the directional cubic convolution interpolation which has been described in the following paper: D. Explaining Convolution Using MATLAB Thomas Murphy1 Abstract Students often have a difficult time understanding what convolution is. But looking at the big picture, you should not use conv2 at all, and use imfilter instead, which does take 'uint8' images. m file that is 140x140 with 20 pixels zero padded on each side. To use "imread", you must have the directory where the image is located in your list of directories. I have Matlab code for convolution in Fourier Transform but I don't know how to implement that in OpenCV. Thank you for pointing the typing errors out. sara: Naz suggested that you'd want to convolve the signal with itself. Using the strategy of impulse decomposition, systems are described by a signal called the impulse response. And it would work for color images, for instance by working on different color places. Example of 2D Convolution. How to convolve an image of a*b*c with a filter of d*e*f?. First, a kernel matrix (or blurring filter) is created. Common image processing include image enhancement, restoration, encoding, and compression. Exposed on Internet March 1, 2011. Do NOT use matlab convolution routines (conv,conv2,filter2 etc). I would like to dedicate today's post to a not-well-known performance trick from my book, that could significantly improve the speed when computing the convolution of two data arrays. MATLAB for Absolute Beginners MATLAB is much easier to learn when you can try everything for yourself in this course for beginners! With more than a million users, MATLAB is a must know programming language for science, engineering, and economics professionals. Convolution Filter. Moving average by convolution. convolution basics including matlab function is covered. Convolution is used in the mathematics of many fields, such as probability and statistics. Convolution in MATLAB(without conv function) | MATRIX Method. Convolution is a neighborhood operation in which each output pixel is the weighted sum of neighboring input pixels. Many elegant programming techniques exist in MATLAB, but none are quite so elegant as the recursive function. Convolving two signals is equivalent to multiplying the frequency spectrum of the two signals. This sample image consist of three phases in three different colors, I am interested in the triple phase points(as shown in pattern image or may be different combinations like this, two whites instead of two gray pixels, but all three should be there-drawn by hand) in this sample image. In Matlab, 2D convolution can be done with the. Convolution in Matlab Without Using Conv(x h) - File Exchange - Free download as PDF File (. The convolution in matlab is accomplished by using conv command. I've been tasked with trying to create a smoothing filter function that smoothes an image without using Conv2. Convolution is similar to cross-correlation. Is a matrix applied to an image and a mathematical operation comprised of integers It works by determining the value of a central pixel by adding the. Note that the centre of the kernel as we sweep across the image is the location where we need to output in the image, denoted by the  symbols. Do NOT use matlab convolution routines (conv,conv2,filter2 etc). The following Matlab project contains the source code and Matlab examples used for beating matlab's convolution function conv for long real sequences!. in both process (space domain and frequency doamin) the output should be same. Learn more about signal system. ) Double loop over all interior pixels. Matlab has extensive help files available online. I am currently working on a project where I need to convolve two images grayscale images (0-255 range). Basic; Tutorial Contents. We have explained about how to change size of image. gpuArrayA — Image to be filtered gpuArray object. Do NOT use matlab convolution routines (conv,conv2,filter2 etc). High-pass filtering works in the same way as low-pass filtering; it just uses a different convolution kernel. Thanks, Spandan! This example shows how you can use imfindcircles to automatically detect circles or circular objects in an image. A perfect example of 2D signal is image. Abstractly, a convolution is defined as a product of functions and that are objects in the algebra of Schwartz functions in. Convolution Remember cross-correlation: A convolution operation is a cross-correlation where the filter is flipped both horizontally and vertically before being applied to the image: It is written: Suppose H is a Gaussian or mean kernel. Because of this, you will have to convolve each filter separately for each image, using the row and column of the image as the 2 dimensions you convolve over. Convolution is implemented in the Wolfram Language as Convolve[f, g, x, y] and DiscreteConvolve[f, g, n, m]. I've been tasked with trying to create a smoothing filter function that smoothes an image without using Conv2. I am using image filtering for an image processing algorithm I'm developing. To simplify and reduce ifs, you should pad the image with zeros before starting your convolution loop. If u is a vector with length n and v is a vector with length m, then their convolution will be of length nm-1 ; Convolution is a commutative operation. I have an imbalanced data set (~1800 images minority class, ~5000 images majority class). Convolution definition is - a form or shape that is folded in curved or tortuous windings. Convolution is a formal mathematical operation, just as multiplication, addition, and integration. Subtract from the original. Note that the centre of the kernel as we sweep across the image is the location where we need to output in the image, denoted by the  symbols. So to avoid this problem adjust the length of x and h to be equivalent to the final length as shown:-. The toolbox supports a wide range of image processing operations, including: - Geometric operations - Neighborhood and block operations. Consider two sequences x1(n) of length L and x2(n) of length M. About Edge Detection: Edge detection is an image processing technique for finding the boundaries of objects within images. MATLAB image processing codes with examples, explanations and flow charts. Bayesian Regression Approach Matlab code The following package and source code is based on A Bayesian Regression Approach to the Inference of Regulatory Networks from Gene Expression Data. This and many other kernels are built into image editing software such as Photoshop. For example, you can filter an image to emphasize certain features or remove other features. I have four columns of data with x and y values of two signals. As I understand it, the splitEachLabel function will split the data into a train set and a test set. Plus, the linearity of convolution entails that if you prove the associativity for the dirac image, then the result extends to other images. but the second one is start plotting from A6-A16 that part I am not able to do it. Do NOT use matlab convolution routines (conv,conv2,filter2 etc). Addition takes two numbers and produces a third number, while convolution takes two signals and produces a third signal. e; copy the first few samples of the signal and append them to the signal. 2D Convolution Matrix in Matlab. mp02: Discrete Convolution GUI This mini project concentrates on the use of dconvdemo a GUI for discrete-time convolution. Second, for 2D images we give first the row, then the column. Convolution filters are a great way to process images for certain features. Learn more about image processing, fourier filtering MATLAB, Image Processing Toolbox. Open Mobile Search. Convolution Mask. While this can be done in terms of a cross correlation, care has to be taken to normalize both input and template, as cross correlation by itself is not invariant to mean shifts. How to plot FFT using Matlab - FFT of basic signals : Sine and Cosine waves June 27, 2019 July 16, 2014 by Mathuranathan ( 101 votes, average: 4. Image convolution You are encouraged to solve this task according to the task description, using any language you may know. Note that this relation only lives for real values on the interval [-0. You would have to write your own code for a modulation (Matlab has a convolution function not in the tools), otherwise you can use its built in function in the signal processing toolbox. convolve (a, v, mode='full') [source] ¶ Returns the discrete, linear convolution of two one-dimensional sequences. Make the routine as efficient as possible: Restrict usage of for loops which are expensive (use matrix multiplications and matlab routines such as dot etc). Here, for classification purposes, I. i don't want to do any auto-correlation. Learn more about digital image processing Image Processing Toolbox imshow expects that that intensity of a double image is in the. e; copy the first few samples of the signal and append them to the signal. This MATLAB code implements the multi exposed image fusion using CNN. The pixels of an image is distributed in 2D spatial domain. There are a lot of convolution functions in matlab, mostly in the signal processing toolbox, so it depends on what you want to do. Convolution. convolution of images Alexandre Damião Introduction to Digital Image Processing by Ms CETL at ABES Engineering College 79,107 views. Yes we can find linear convolution using circular convolution using a MATLAB code. Reference: B. Convolution is used in the mathematics of many fields, such as probability and statistics. In mathematics, the convolution theorem states that under suitable conditions the Fourier transform of a convolution is the pointwise product of Fourier transforms. Convolution Filtering: Unsharp Masking Unsharp masking is a technique for high-boost filtering. Hi John, I did download the Signal Processing Toolbox. As this example demonstrates, you can visually analyse the image quality after each iteration by plotting it. Example 4: I got a penny image from MATLAB (load penny) and use C^1 qunitic spline to fit thepenny data (128x128) based on domain decomposition method (a joint work with L. I'm currently attempting to convolve two exponential(one gaussian) functions in order to create a convolved equation in Matlab that I can then use in the custom equation section of the Curve Fitting application to fit to a distribution in order to extract certain parameter values for multiple datasets.