convolution with fft for image in image search/similarity

Started by Andreas in comp.dsp14 years ago 3 replies

Hello! I have been trying to implement an image in image search algorithm using fft, as described in the dspguide, chapter 24...

Hello! I have been trying to implement an image in image search algorithm using fft, as described in the dspguide, chapter 24 (http://www.dspguide.com/), using FFT Convolution. As far as I have understood it, the search image is used as some kind of a filter (like sharpen, etc.) on the original image (in which I search) in order to give the resulting image a distribution of similarity of...


Image Types in Matlab

Started by Nina in comp.dsp11 years ago

Hi, I have no experinece in either image processing or matlab. I am a little confused about image types and image processing toolbox...

Hi, I have no experinece in either image processing or matlab. I am a little confused about image types and image processing toolbox in matlab, and i appreciate if anyone could please clarify these confusions. So here is my problem: According to image processing tool box users's guide, an intensity image is stored in a single 'intensity matrix' that contains double precision values rang...


Noise characterization of wavelet coefficients

Started by g in comp.dsp13 years ago 1 reply

Hi, I hope this question about wavelets is not too far off topic in this forum... I have some image data with noise for which the noise...

Hi, I hope this question about wavelets is not too far off topic in this forum... I have some image data with noise for which the noise statistics (mean, variance) are known : noisy image = true image + noise in image domain In my case, the mean and variance is not constant over the image (correlated noise). When I perform a wavelet transform on this noisy image, I presume I can ...


Wavelets and Reflection image question

Started by Anonymous in comp.dsp9 years ago

Hi all, I've recently begun trying to understand the fundamentals of lossy image compression via transforms such as DCT and...

Hi all, I've recently begun trying to understand the fundamentals of lossy image compression via transforms such as DCT and Wavelets (CDF9/7). In a paper I was reading it suggested that prior to applying a forward transform that a "reflection image" of the original image be created. This involves flipping the image vertically and horizontally and copy those flipped variants above, be...


image in image search

Started by Andreas in comp.dsp14 years ago 4 replies

Hello! I am trying to implement an algorithm which is supposed to find the best match of a given (small) image in a larger image. I have...

Hello! I am trying to implement an algorithm which is supposed to find the best match of a given (small) image in a larger image. I have thought about a few (naive) ways of implementation, and recently have been pointed at FT and wavelets, which - if applicable - sound rather interesting for my problem. So I was wondering whether you can give me any tips on whether using those transfo...


Image compression DSP

Started by amerdsp in comp.dsp11 years ago

Greetings, I am looking for a low power image compression for a mobile application. It is meant to compress image data from an image...

Greetings, I am looking for a low power image compression for a mobile application. It is meant to compress image data from an image sensor so it can be transmitted over GPRS. Does anyone have any recommendations? Currently I am still looking for a microcontroller, probably a PIC to do the control functions. I am not sure if any microcontroller will be fast enough to be able to perfo...


SDRAM is too fast??

Started by Laplace in comp.dsp10 years ago 1 reply

Hi! I'm developing an image processing algorithm for the ADSP21369 and trying it into de EZ-KIT 21369... I load the image (640*480 bmp image)...

Hi! I'm developing an image processing algorithm for the ADSP21369 and trying it into de EZ-KIT 21369... I load the image (640*480 bmp image) with the Image Viewer into SDRAM and process it directly from SDRAM. Trying to do it with the DMA I found that there are no significatively difference betwen them. That's possible?? Or I'm doing somethimg wrong?? I measure times like this: STA...


Need some help for FFT2 of an Image

Started by Mechmatlab in comp.dsp9 years ago

Hi all, I am a beginner in matlab and i seriously need your help. MY PROBLEM: I have a grayscale image(1024 X 1280) of a pyrovalve(a...

Hi all, I am a beginner in matlab and i seriously need your help. MY PROBLEM: I have a grayscale image(1024 X 1280) of a pyrovalve(a valve used in rocket engines, looks like a small piston cylinder arrangement). I was asked to do fourier analysis(2D) on this image. For that i took FFT2 of the image. I can get the absolute frequency values. I have to make a 3D plot of the frequency mag...


when should I pad image before filtering?

Started by lucy in comp.dsp12 years ago 2 replies

I am always confused by the padding for image filtering. I have an 270x230 "image" and is to be filtered with a 250x250 "filter". I have...

I am always confused by the padding for image filtering. I have an 270x230 "image" and is to be filtered with a 250x250 "filter". I have made sure that the sum of all filter coefficients sum to be 1. In Matlab, sum(sum(filter)) =1.0000, then I do image filtering: result=imfilter(image, filter, 'same'); so the result is the also a 270x230 image... since I've used 'same' option,...


2D FFTW Inverse FFT does not give original image when /n

Started by adam3914 in comp.dsp8 years ago 4 replies

I have what I have to assume is a stupid mistake on my part. I am able to take the fft of an image and get back the half of the transformed image...

I have what I have to assume is a stupid mistake on my part. I am able to take the fft of an image and get back the half of the transformed image as I should. When I try to do a inverse fft on the data from the fft I get really big numbers like 10^71 size numbers. When I would expect to get my original image times 640*480, the size of my image. My first question is do I have to create the othe...


Entropy of image

Started by Sylvia in comp.dsp8 years ago 1 reply

Hi, For a 2D image with intensity values I(x_i) where x_i is the location of ith pixel within the image, is there any relationship (correlation...

Hi, For a 2D image with intensity values I(x_i) where x_i is the location of ith pixel within the image, is there any relationship (correlation etc.) of following expression sum_i I(x_i) log (I(x_i)) with the entropy of an image? Sylvia


Fourier Transform

Started by Anonymous in comp.dsp9 years ago 4 replies

I have a problem with one of my assignments and I hope any of you could help me out. Take the phase of the clown image(file clown.tif) and the...

I have a problem with one of my assignments and I hope any of you could help me out. Take the phase of the clown image(file clown.tif) and the magnitude of the Mandrill image (Mandrill.tiff) and combine them into a new synthetic image. Show the magnitude plot for the clown image,the phase plot for the mandrill image and inverse transformation of the result using(ifft2).


different resolution on photographic correlation

Started by sangthong in comp.dsp9 years ago 6 replies

Hi, guys I've got a question on photographic correlation for doing inspection by cross correlation. I can find sub-image inside the original...

Hi, guys I've got a question on photographic correlation for doing inspection by cross correlation. I can find sub-image inside the original image, however, I don't have an idea if the images have been taken at far different distances, so the resolution of the big image and sub-image are different. Can anybody tell me theoratically on this? thank you very much. Sangthong


Image correlation via FFT. Why doesn't this work?

Started by typewriter in comp.dsp10 years ago 14 replies

Hello, I have a program that performs FFT convolution to search for occurrences of a small image inside another image. I feel like I...

Hello, I have a program that performs FFT convolution to search for occurrences of a small image inside another image. I feel like I understand the concept, but my program doesn't do what it should. The small search image is simply cut out from the larger image, so I should see a bright spike in the resultant FFT convolution. But I am seeing a very ambiguous result. I created a web...


Image Compression Using Fourier Transforms

Started by Anonymous in comp.dsp8 years ago 24 replies

I was wondering if there was a relatively straightforward algorithm for compressing image using Fourier transforms. I was thinking that I could...

I was wondering if there was a relatively straightforward algorithm for compressing image using Fourier transforms. I was thinking that I could transform an image into frequency space and then perform a lowpass filter on the image to set all the lesser frequencies to zero, then perform a run-length-encoding on the data to pack the zeroes. However, I have been running into trouble with this me...


Image Processing Algorithm Development Software Engineer

Started by sduhl in comp.dsp11 years ago

Looking for an experienced image processing algorithm development software engineer. Familiarity with TI 642 DSP processors, C++, and Code...

Looking for an experienced image processing algorithm development software engineer. Familiarity with TI 642 DSP processors, C++, and Code Composer is required. The candidate will be required to integrate and develop image compression and image stabilization algorithms. Experience in other image processing functions is beneficial. Location: Albuquerque NM Duration: 6 month Rate: $50 - $90/...


Image/video processing/enhancement tool

Started by Image in comp.dsp9 years ago 5 replies

Is there a free tool for Matlab based (or other) for doing image/video enhancement: 1. Zooming in using various interpolation (bi-cubic...

Is there a free tool for Matlab based (or other) for doing image/video enhancement: 1. Zooming in using various interpolation (bi-cubic etc.), 2. image enhancement using spatial correlation, 3. image enhancement using succeeding images series. Thanks, IM


image subsampling problem???

Started by walala in comp.dsp13 years ago 32 replies

Dear all, I want to ask how to downsample an image and avoid aliasing? How to make sure that an downsampled image can be reconstructed...

Dear all, I want to ask how to downsample an image and avoid aliasing? How to make sure that an downsampled image can be reconstructed perfectly? I guess I am too acquainted with time as my x-axis, now when it comes to 2D spatial domain, I get perplexed... Can anybody give me some enlightenment? Thanks a lot, -Walala


Fast Normalized Cross-Correlation

Started by Anonymous in comp.dsp10 years ago

Hi. All, I'm working on Image processing and using Fast Normalized Cross- Correlatino method to compare the template image with the...

Hi. All, I'm working on Image processing and using Fast Normalized Cross- Correlatino method to compare the template image with the Sample image. Fot the theory I use, I need to undestand two terms. 1) Weighted sum and 2) Rectangulare basis function. How should I apply this two the template image ? If anyone knows, reply asap. Thanks & Regards, Chauhan P.D


Re: ANNOUNCEMENT: New image format

Started by Thomas Richter in comp.dsp10 years ago

John Costella schrieb: > Thanks, mate; I've tried to break it but my resources are limited. > (Would be much easier if my name was Bill...

John Costella schrieb: > Thanks, mate; I've tried to break it but my resources are limited. > (Would be much easier if my name was Bill Gates, but then > everyone would be throwing things at me.) Could you send me > the image that killed it? (Or are you telling me that it dies for all > images with that build?) Pretty any image does that, see below for what I believe the problem is. >