Rank: 59 based on 832 downloads (last 30 days) and 18 files submitted
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David Young

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Company/University
University of Sussex and University of Southampton
Lat/Long
50.86579, -0.086335

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Professional Interests:
Image Processing

 

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Files Posted by David View all
Updated   File Tags Downloads
(last 30 days)
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04 Sep 2014 Screenshot Hough transform for circles A Hough transform function for detecting circles, optimised to allow search over radii. Author: David Young hough transform, circle, image analysis 194 39
  • 4.52632
4.5 | 20 ratings
30 Jun 2014 A multidimensional map class MapN provides a map class similar to containers.Map, but with multidimensional keys. Author: David Young map, container, containers, memoize, containersmap, oop 25 7
  • 4.66667
4.7 | 4 ratings
20 Mar 2014 Fast 2-D convolution Speeds up many 2-D convolutions using the SVD; also finds a fast approximation in other cases. Author: David Young 2d, convolution, filtering, svd, image processing 61 5
  • 5.0
5.0 | 5 ratings
20 Mar 2014 Gradients with Gaussian smoothing Grey-level gradients are estimated using Gaussian smoothing followed by symmetric differencing. Author: David Young image processing, image smoothing, gaussian smoothing, gradients, first derivative, noise reduction 38 0
  • 5.0
5.0 | 1 rating
20 Mar 2014 TerraSAR-X and TanDEM-X tools Read and convert TerraSAR-X and TanDEM-X COSAR files Author: David Young sar, insar, synthetic aperture ra..., interferometric synth..., terrasarx, tandemx 25 0
Comments and Ratings by David View all
Updated File Comments Rating
23 Sep 2014 Canny edge detection in 2-D and 3-D A Canny edge detector for two-dimensional image and three-dimensional volume data. Author: David Young

Hi Siddharth, It looks as if checkattributes is not on your path. Please make sure that you downloaded the complete submission and all the files are in a folder on your MATLAB path. It's best to download the zip file and unpack it rather than downloading individual functions.

11 Sep 2014 Log-polar image sampling Resamples an image from a conventional grid to a log-polar grid, and back. Author: David Young

Hi Daniel, The differences from the original are almost inevitable, because the log-polar transform is usually lossy. Unless you use a huge output array, the pixels in the outer rings will be further apart than the original image pixels. When you transform back, there's no way to recover the lost information, and so the resolution suffers. Antialiasing won't be able to help fundamentally.

Both functions use *imtransform* with default interpolation. (I ought to update to *imwarp* sometime.) It might be possible to get some improvements in quality by changing the interpolation rule - you'd need to learn about *makeresampler* to generate a resampler to give to imtransform. It still will not restore the original image though.

09 Sep 2014 Canny edge detection in 2-D and 3-D A Canny edge detector for two-dimensional image and three-dimensional volume data. Author: David Young

Hi tong luo, This looks like a version problem also. Please try replacing this line in the definition of checkthresh:

{'nonnan' 'real' 'finite' 'nonnegative' 'nondecreasing'}) && ...

with this:

{}) && ...

This removes some checking, but that probably will not matter, and I hope will avoid the warning.

I am concerned, though, that the warning does not account for the result you observe. Please let me know if that continues to be a problem.

04 Sep 2014 Hough transform for circles A Hough transform function for detecting circles, optimised to allow search over radii. Author: David Young

Thank you, zhan kunhe - you are absolutely right. Now fixed.

09 Jul 2014 Canny edge detection in 2-D and 3-D A Canny edge detector for two-dimensional image and three-dimensional volume data. Author: David Young

Hi ├ľnder, I think the only change you need to make is to replace inp.addParameter with inp.addParamValue wherever it occurs. If there are other problems, please let me know what goes wrong.

Comments and Ratings on David's Files View all
Updated File Comment by Comments Rating
23 Sep 2014 Canny edge detection in 2-D and 3-D A Canny edge detector for two-dimensional image and three-dimensional volume data. Author: David Young Young, David

Hi Siddharth, It looks as if checkattributes is not on your path. Please make sure that you downloaded the complete submission and all the files are in a folder on your MATLAB path. It's best to download the zip file and unpack it rather than downloading individual functions.

22 Sep 2014 Canny edge detection in 2-D and 3-D A Canny edge detector for two-dimensional image and three-dimensional volume data. Author: David Young Siddharth

Hi,

I got an error while using this program. Do you know what am i doing wrong?

Error using gsmoothn>checkinputs (line 128)
The value of 'Region' is invalid. Undefined function 'checkattributes' for input
arguments of type 'cell'.

Thanks

17 Sep 2014 Log-polar image sampling Resamples an image from a conventional grid to a log-polar grid, and back. Author: David Young Phillip

Works as advertised, good job. Am using this to recover rotation/scale for image registration.

11 Sep 2014 Log-polar image sampling Resamples an image from a conventional grid to a log-polar grid, and back. Author: David Young Young, David

Hi Daniel, The differences from the original are almost inevitable, because the log-polar transform is usually lossy. Unless you use a huge output array, the pixels in the outer rings will be further apart than the original image pixels. When you transform back, there's no way to recover the lost information, and so the resolution suffers. Antialiasing won't be able to help fundamentally.

Both functions use *imtransform* with default interpolation. (I ought to update to *imwarp* sometime.) It might be possible to get some improvements in quality by changing the interpolation rule - you'd need to learn about *makeresampler* to generate a resampler to give to imtransform. It still will not restore the original image though.

11 Sep 2014 Log-polar image sampling Resamples an image from a conventional grid to a log-polar grid, and back. Author: David Young Daniel

This is a great start for me. I'm trying to model foveal vision, but when I use the logsampback function the output image will have significant variations from the original that look like aliasing. Do you know of a way to add anti-aliasing into the logsample function?

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