## Forums Search for: Image

## convolution with fft for image in image search/similarity

inHello! 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

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

inHi, 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

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...

## Entropy of image

inHi, 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

## image in image search

inHello! 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...

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

inI 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...

## when should I pad image before filtering?

inI 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,...

## Regarding DCT

inHi All, I am performing Integer DCT on Lena image. I am using " C "& i am not able to reconstruct the image correctly. Before applying DCT I...

Hi All, I am performing Integer DCT on Lena image. I am using " C "& i am not able to reconstruct the image correctly. Before applying DCT I am subtracting 128 from all pixels of input image. After IDCT i am adding 128 to the result image. I want to compare my results with MATLAB . Is anybody know how to use dct i.e. dct2 function of MATLAB? if anyone has the related code in MATLAB please...

## SDRAM is too fast??

inHi! 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...

## Image compression DSP

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...

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

inHello, 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...

## Need some help for FFT2 of an Image

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...

## Fourier Transform

inI 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).

## Image Compression Using Fourier Transforms

inI 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...

## Newbie question

inI have a 2d signal (an image, actually) of which I want to calculate ACF. I tried to use the IFFT/FFT approach, but when I rotate the image...

I have a 2d signal (an image, actually) of which I want to calculate ACF. I tried to use the IFFT/FFT approach, but when I rotate the image I notice some strange effects (something aliasing-like). So I tried to pad my image both vertically and horizontally with zeros, doubling its dimension before calculating the FFT. Am I doing right? Someone can help me? Thank you Lorenzo

## Image Processing Algorithm Development Software Engineer

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/...

## different resolution on photographic correlation

inHi, 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

## how to compensate for low dynamic range monitors?

inHi all, I have a bright image which is taken using good camera, and I upsampled it to a higher resolution(say NxN larger size)... and then...

Hi all, I have a bright image which is taken using good camera, and I upsampled it to a higher resolution(say NxN larger size)... and then applied some image processing, color space conversion, gamma transformation, inverse gamma, filtering, etc... and the new image look dark...(or equavalent, the LCD monitor does not support the new image due to its limited dynamic range... what can ...

## image subsampling problem???

inDear 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