Obviously there is no answer for this "Given this standard deviation how many filter samples are needed?" for all images. For example given a SD of 15, you'll never achieve that in a uniform image no matter how many samples you take. Even for images WITH an SD of 15 you'll never achieve that. So you're going to have to restate your question.

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5/13/2010 10:25:54 AM

On May 13, 12:25=A0pm, ImageAnalyst <imageanal...@mailinator.com> wrote: > Obviously there is no answer for this "Given this standard deviation > how many filter samples are needed?" for all images. =A0For example > given a SD of 15, you'll never achieve that in a uniform image no > matter how many samples you take. =A0Even for images WITH an SD of 15 > you'll never achieve that. =A0So you're going to have to restate your > question. Thanks for the quick reply. I don't exactly follow. To make it clearer for me could you please explain what a filter sample is and how it relates to standard deviation? The image is the standard "cameraman" image (512x512 grayscale), which I am smoothing using a Gaussian filter with SDx=3D3,SDy=3D3. I don't know if this changes the question.

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5/13/2010 10:47:49 AM

> > Secondly, what is the relationship between standard deviation and > filter samples? The question I need to answer is as follows: "Given > this standard deviation how many filter samples are needed?" If > someone could point me in the right direction, that would be great. I like to select the window size that is about 3*sigma in each side: n = ceil(6*sigma+1) And to enforce minimum of 3, n = max(ceil(6*sigma+1), 3) Bruno

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5/13/2010 11:14:07 AM

On May 13, 6:47=A0am, J B <trifinit...@googlemail.com> wrote: > On May 13, 12:25=A0pm, ImageAnalyst <imageanal...@mailinator.com> wrote: > > > Obviously there is no answer for this "Given this standard deviation > > how many filter samples are needed?" for all images. =A0For example > > given a SD of 15, you'll never achieve that in a uniform image no > > matter how many samples you take. =A0Even for images WITH an SD of 15 > > you'll never achieve that. =A0So you're going to have to restate your > > question. > > Thanks for the quick reply. > > I don't exactly follow. To make it clearer for me could you please > explain what a filter sample is and how it relates to standard > deviation? > > The image is the standard "cameraman" image (512x512 grayscale), which > I am smoothing using a Gaussian filter with SDx=3D3,SDy=3D3. I don't know > if this changes the question. ---------------------------------------------------------------------------= --------------------------- Never mind - I got the standard deviations confused. I thought you were trying to get a certain specified SD in the image after you filtered it, but you were actually talking about the width of the Gaussian kernel. Did you see the additional option in the help for fspecial?? "h =3D fspecial('gaussian', hsize, sigma) returns a rotationally symmetric Gaussian lowpass filter of size hsize with standard deviation sigma (positive). hsize can be a vector specifying the number of rows and columns in h, or it can be a scalar, in which case h is a square matrix. The default value for hsize is [3 3]; the default value for sigma is 0.5." hsize is basically the window width of the kernel you're going to scan with, for example 21 pixels by 21 pixels, or 100 by 100. sigma is the width of the Gaussian shape that falls inside that window, for example 3 pixels. Understand now? Obviously you don't need the window width to be much wider than about 6 or 7 sigmas because the Guassian will flatten out by the time it gets to the edge.

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5/13/2010 2:47:44 PM

Hi all, I am using an isotropic Gaussian filter with standard deviation sigmaX=3, sigmaY=3. Firstly, I would like to ensure that my matlab code is correct in achieving this: % Isotropic Gaussian filter with standard deviation sigmaX=3, sigmaY=3 filter = fspecial('gaussian', [3 3], 3); If not, what is wrong with it, and how do I fix it? Secondly, what is the relationship between standard deviation and filter samples? The question I need to answer is as follows: "Given this standard deviation how many filter samples are needed?" If someone could point me in th...

Dear members, I would like to inform you that we have released our last version of the open source library "Filters". We will appreciate your feedback. link : http://filters.sourceforge.net/ Regards In short, no source code = crap. Come back when you've got something real to download, a few demos and some API's don't equate to much these days... edurand wrote: > Dear members, > I would like to inform you that we have released our last version of > the open source library "Filters". We will appreciate your feedback. > link : http://filters.so...

I want to smooth an image using an isotropic Gaussian filter with standard deviation of =F3x, =F3y =3D 3. To achieve this, can I use the fspecial function to create the smoothing filter as follows: gauss_filter =3D fspecial('gaussian', [x y], 3); With [x y] being the size of the filter to apply to the image. If not, what should I be using instead? Also, what is the relationship between the number of filter samples required and the standard deviation used? Thanks. ...

I must do a Gaussian Filter on image, I have matrix data image in a 100x100 matrix. I generate a 7x7 gaussian matrix for filtering, how do I padding the gaussian matrix for obtain a 100x100 matrix ? with zeros value around gaussian value ? thank you so much. anyone can help me ? ...

Hi all, This is a continuum of the question I post one moment ago. I've obtained a 11x11 impulse response for that 2D low pass Butterworth filter of 7th order and 0.2 cutoff frequency(normalized frequency range [-0.5, 0.5])... My friend claimed that the following 11x11 h impulse response have negative values in it so it is no good for image filtering... (btw, why are there negative values? ) He suggests that I forget these fancy filters and use a plain Gaussian filter for low pass filtering... however I looked into the "fspecial" command in Matlab image toolbox... and I ...

dear all, I am facing the following problem that I need your help: We have in our experiments some special images need to be processed. My task is to look at these images and see how to improve/enhance them. In fact we/I have no idea on how much enhancement we can get. So what I've done in the past month is to play with different kind of filters to try on the images. We use PSNR as judgement. It turns out I found a Gaussian 3x3 filter has particularly high enhancement to the images, comparing with other filters provided by Matlab, such as "laplacian", "averaging"... ...

Hi, My program is to read some images and then high pass filter to filter the image and plot out the rms values. I’m able to read and display the image. But the filter got problem. The error message: ??? Undefined function or variable 'filterarray'. Error in ==> D:\MATLAB6p5p1 \work\signalimage\FocusImages\new.m On line 47 ==> lengthoffilter=length(filterarray); I can’t continue. Anybody know how to troubleshoot? Below is the program. Thank you. Regards, Sem -------------------------------------------------- clc; close all; clear all; for picture=1:...

Hi,I have a problem with my GUI.. In my GUI there are two axes and two buttons.. User ,will click in the first button ,he will load a image and the image will be shown in the wirst window of my GUI. Then the user will click on the "segmention" button and the segmented image will be shown in the second window. My problem is ,that the Segment_Callback can't read the file name. I posted you my code and the errors. Thanks a lot in advance!! function OpenImage_Callback(hObject, eventdata, handles) [filename, user_canceled] = imgetfile axes(handles.SimpleImage) title(...

Hello, I have a question regarding how to populate the Irradiation Event UID in the following scenario: Image A is acquired on a DR or CR system. Image A is given an Irradiation Event UID. Image B is created by processing Image A using different image processing parameters. Should Image B have the same Irradiation Event UID as Image A since they both come from the same irradiation event? It seems that they should. If both Image A and Image B are given the same Irradiation Event UID and a Radiation Dose Report is created, is there any problem with having more than one imag...

Hi,I have a problem with my GUI.. In my GUI there are two axes and two buttons.. User ,will click in the first button ,he will load a image and the image will be shown in the wirst window of my GUI. Then the user will click on the "segmention" button and the segmented image will be shown in the second window. My problem is ,that the Segment_Callback can't read the file name. I posted you my code and the errors. Thanks a lot in advance!! function OpenImage_Callback(hObject, eventdata, handles) [filename, user_canceled] = imgetfile axes(handles.SimpleImage) title(...

Hi all, I am facing a headache question in image filtering... I want to apply a low pass filter to an RGB image... I used Gaussian filter, using Matlab "fspecial" command h=fspecial('gaussian', [31, 31], 5); .... and I am setting the cutoff frequency quite low because I really want to blur the images quite heavily... I applied the filter to each of the RGB planes, using the Matlab "imfilter" command. My input image was made sure to be within [0, 1] for each plane. So for each RGB plane, the range is [0, 1], [0, 1], [0, 1]. The mean of each channel are: R:...

why Gaussian smoothing is commonly used with edge detection? what is the most suitable smoothing method for __edge detection algorithm? Is it Gaussian smoothing? If so, why? ...

Hi, If I am using scipy.ndimage.gaussian_filter() for filtering an image, how to do the inverse filtering? In general how to do this using scipy.ndimage? Thanks suresh In article <5bfefbb6-89a8-49f6-9f02-7d36dfbc0f16@c29g2000yqd.googlegroups.com>, suresh.amritapuri <suresh.amritapuri@gmail.com> wrote: > >If I am using scipy.ndimage.gaussian_filter() for filtering an image, >how to do the inverse filtering? In general how to do this using >scipy.ndimage? http://projects.scipy.org/mailman/listinfo/scipy-user -- Aahz (aahz@pythoncraft.com) &...

i have to filter my images by Gabor filters. I write my Gabor function. It takes the parameters of "Size", "Standard Deviation", "Period" and the "Orientation of gabor shell". My purpose is to find rectangles in the images. After filtering, i will binarize my images, and i will approximately find the places of rectangles in my images. That seems ok. but every images have different backgrounds and illumination level. Although i have done preprocessing, the output of filtering is not good. I have chose the parameters of filters by trial and err...

Hi, Have anyone done any image processing function called matched filtering. I have two input images (same size). The output should be the correlation value between two image. I tried corr2 function but it doesn't work well when the image is shifted to left or right (not shifting invariant). I hope that matched filtering will solve this problem. thanks xcorr2 or conv2 should do the job, if you design your matched filter accordingly. /Johan yo wrote: > Hi, > Have anyone done any image processing function called matched > filtering. I have two input images (same size). T...

Hi, I have an RGB image and without converting it to grayscale I want to do median filtering. Is it possible , if so how ? I tried to create the median filter but it give me following error Function ORDFILT2 expected its first input, A, to be two-dimensional. Error in ==> ordfilt2>ParseInputs at 135 iptcheckinput(A, {'numeric','logical'}, {'2d','real'}, mfilename, 'A', 1); Error in ==> ordfilt2 at 51 [A,order,domain,s,padopt,msg] = ParseInputs(varargin{:}); Error in ==> medfilt2 at 57 b = ordfilt2(a, order1, domain, padopt); Erro...

Hi, I am quite new to Matlab. Is there a built-in function to apply a gaussian filter over a color image? If not, any hints on how to do it? Also, if there is a built-in function, can I tell it to handle edges differently (like, using kernel renormalization?) Thanks a lot in advance. Did you try this? filterMask = gausswin(dy) * gausswin(dx)'; imageOut = filter2(filterMask, imageIn); Where dx and dy is the size of the rectangular filter mask. I would do the edge handling manually by padding, but maybe there is a better way to do that. Regards Markus [url=http://zvxcxw.googlepages...

i can any process with matlab to image spot5 satellite. You have any practice with this? tank regards ...

hi to all Im new to image processing and also to matlab. I have a project which needs to extract blood vessels from retinal image by using matched filtering and It looks like I have to desgin one but I have no idea what is a matched filter. Can some please explain me image processing with matched filtering thank you ANIL Why do you need to use a matched filter? Why not use any method that you can think of that will work? If it's your homework problem, then review your notes from the class lectures or ask your professor. If you have a MATLAB question, such as how to use im...

Hi, I have a basic question on image processing, after FT, I got the casted image on different colors, or different freq. Next is to pass through a filter to get the freq that I want. I am wondering, I can just pick up any freq I want, and the band of freq I want. Why do I have to construct a filter? Is it really needed? Or how a filter is being used in image processing? thanks PZ PZ wrote: > Hi, > > I have a basic question on image processing, after FT, I got the casted > image on different colors, or different freq. Next is to pass through a > filter to get the freq tha...

Hi my name is Alam, and now i'm working for my final project in my university. My task is to set up a vision based tracking system. It use a single firewire camera to detect the presence of an object using some image processing algorithm that give an information about object coordinate position. I use this information as the input for Kalman Filter so that i can predict the object position for the next state of my system. I just want to know if I can do that job using LabView and CVS 1454 ( because my supervisor order me to use it ). If it is possible I also want to know how can i send ...

Hey guys. I kinda need some help here. I'm doing some image processing and I'm programming some filters. Here's the case of a high pass filter, for instance with a 5x5 kernel which has this form (I stole it from the IPP): 0 -1 -1 -1 0 -1 -1 -1 -1 -1 -1 -1 21 -1 -1 -1 -1 -1 -1 -1 0 -1 -1 -1 0 So, the negative coefficients here may turn the result of applying the kernel to be negative for a particualr pixel, or maybe bigger than 255. Is there any normalization technique? I tried uint8 but the results are far worse than what I get when applying the filter in IPP Than...

Hi, I want to use sinc filter for image processing. As I understand for its theory this can be suitable for edge detection operation.How can I do this in Matlab? Could you help me about this operation? Thanks. On Sep 22, 4:28=A0am, "elysion87 " <saki...@gmail.com> wrote: > Hi, > > I want to use sinc filter for image processing. As I understand for its t= heory this can be suitable for edge detection operation.How can I do this i= n Matlab? Could you help me about this operation? > Thanks. ----------------------------------------------------------- Yes. Set u...

Hi, i am new to matlab. I am currently processing sets of data, which the data is in 520x688 pixels. Now, for example in the matrix 520x688, there are some values that more than the threshold value, say my threshold value is 3000, and say we take only 7x4 array like below 2330 2689 2072 2864 2763 2865 2695 2450 4210 2550 2543 2560 2654 2986 2564 2564 2564 2564 3514 2014 2045 2465 2555 2987 2106 2541 2644 2304 so, in that matrix, i have got 2 values that is more than 3000, which are 4210 and 3514. So what i wanted to do is the matlab to find the value that is more than 3000, an...

Is there some way to adjust the horizontal pixel line in an image so that a shift is removed introduced during collection of the image of the object? I believe this is a registration problem similar to correcting for movement during image aquisition, but I have not found any m files that can do this. Blur removal is not adequate since the 'blur' is nonuniform. Short of adjusting each line manually, I believe this line adjustment can be accomplished via an m file that lets one use the cursor to move the line or introduce a function that is anti-phase related to the shift. Thanks for an...