Rank: 53 based on 1005 downloads (last 30 days) and 19 files submitted
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David Young

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University of Sussex and University of Southampton
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50.86579, -0.086335

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Files Posted by David Young View all
Updated   File Tags Downloads
(last 30 days)
Comments Rating
02 Dec 2014 Screenshot Rotate images with automatic cropping The blank triangles that appear in the corners of rotated images are cropped away. Author: David Young image processing, rotate image, crop image 35 0
04 Nov 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 29 3
  • 3.0
3.0 | 2 ratings
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 239 41
  • 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 14 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 58 5
  • 5.0
5.0 | 5 ratings
Comments and Ratings by David Young View all
Updated File Comments Rating
19 Nov 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 Murari, please see my response to Önder below.

04 Nov 2014 Gradients with Gaussian smoothing Grey-level gradients are estimated using Gaussian smoothing followed by symmetric differencing. Author: David Young

Thank you Jess. I had left checkattributes() out of the zip file. Now updated.

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

Hi YIBO, If you change the radius range in the data to start from 16 rather than 15 (so you have "radii = 16:1:40;") then it finds all the coins again.

The demo must have worked with the original radius range when I submitted it. I do not know what has changed to produce the new behaviour. At some point I will update the demo. This does illustrate that the process is verysensitive to the values of the parameters, but this is a property of the algorithm rather than of my particular implementation.

I tried using the image at http://imgur.com/ls65Kwi and my circle detection code works perfectly, detecting all 14 circles without any changes to the parameters in the demo, except of course for the number of circles to find. Is the problem just that you need to increase the number of circles to find from 10 to 14?

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.

Comments and Ratings on David Young's Files View all
Updated File Comment by Comments Rating
19 Nov 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 David Young

Hi Murari, please see my response to Önder below.

19 Nov 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 Murari Mandal

Hi David, i am using matlab13a and getting this error-

No appropriate method, property, or field addParameter for class inputParser.

Error in canny (line 207)
inp.addParameter('Region', 'same');

19 Nov 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 Murari Mandal

Hi David, i am using matlab13a and getting this error-

No appropriate method, property, or field addParameter for class inputParser.

Error in canny (line 207)
inp.addParameter('Region', 'same');

04 Nov 2014 Gradients with Gaussian smoothing Grey-level gradients are estimated using Gaussian smoothing followed by symmetric differencing. Author: David Young David Young

Thank you Jess. I had left checkattributes() out of the zip file. Now updated.

04 Nov 2014 Gradients with Gaussian smoothing Grey-level gradients are estimated using Gaussian smoothing followed by symmetric differencing. Author: David Young Jess

I'll definitely boost my rating if you fix the bugs and let me know! Thanks for posting!

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