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Richard

E-mail: richard.walker@st.com

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Comments and Ratings by Richard		View all 1 - 2 of 2
Updated	File	Comments	Rating
18 Nov 2009	real2rgb & colormaps Converts intensity matrices into truecolor images. Author: Oliver Woodford	Hi Oliver. I don't understand what happens when a colour map with more than 256 elements is requested. I'm trying to create a jet colour map with 1024 elements to display a 10 bit image using the image function. If I do this using either your version of jet or the Matlab one, I get the same result - all blue! 512 creates blue and green strips. 300 elements gives the normal jet colour map between 0 and 255, then it looks like it starts over again from blue. This is not what I would expect - values lower than 256 correctly fit the full colour range into the number of colour map entries requested - I don't see why this should be any different for larger colour maps. The work around I'm using is to use pcolor instead of image to plot the data, as this seems to work with a smaller (presumably 256 element) colour map and map the data onto this. While this works, I don't like the pcolor function very much. It's not intended for displaying images. The axes labels align with grid lines instead of pixels, the data cursor selects points instead of pixels, and I need to have an extra row and column of data. Is there a way of getting a 1024 element colour map that behaves as would be expected? Thanks! Richard.
02 Apr 2009	Multicore - Parallel processing on multiple cores This package realizes parallel processing on multiple cores/machines. Author: Markus Buehren	Brilliant tool! Great being able to sit back and watch a progress bar sliding along as a room full of computers gets to work doing your simulation. I have a question though - what dimensions are typically used for parameterCell? I've tried doing some large multidimensional runs (e.g. 4x150x10) and things seemed to grind to a halt - I'm still looking into it, just wondered if the dimensions I'm using are typical or too large. Cheers. Great work, Richard.

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File	Multicore - Parallel processing on multiple cores
File	real2rgb & colormaps

Files Matching Richard's Watch List				View all 1 - 2 of 2
Updated	File	Tags	Downloads (last 30 days)	Comments	Rating
25 Aug 2009	Multicore - Parallel processing on multiple cores This package realizes parallel processing on multiple cores/machines. Author: Markus Buehren	distributed computing, parallel computing, multicore processing, parallel processing, multiple core, distributed processin...	149	40	4.68571 4.7 \| 38 ratings
13 Apr 2009	real2rgb & colormaps Converts intensity matrices into truecolor images. Author: Oliver Woodford	false color, sepia, ind2rgb, colormap, intensity, truecolour	158	4	4.66667 4.7 \| 3 ratings

Comments and Ratings Matching Richard's Watch List			1-5 of 50
Date	File	Comment by	Comments	Rating
18 Nov 2009	real2rgb & colormaps Converts intensity matrices into truecolor images.	Oliver Woodford	Richard: This issue is do do with the way MATLAB deals with the colormap, rather than the colormap itself, which is as it should be. MATLAB can only handle 256 level colormaps for indexed images (on Windows). Pcolor avoids the problem. So does using truecolor (rather than indexed) images. You can use real2rgb to generate a truecolor image from your 1024 level colormap and your indexed image.	Comment only
18 Nov 2009	real2rgb & colormaps Converts intensity matrices into truecolor images.	Richard	Hi Oliver. I don't understand what happens when a colour map with more than 256 elements is requested. I'm trying to create a jet colour map with 1024 elements to display a 10 bit image using the image function. If I do this using either your version of jet or the Matlab one, I get the same result - all blue! 512 creates blue and green strips. 300 elements gives the normal jet colour map between 0 and 255, then it looks like it starts over again from blue. This is not what I would expect - values lower than 256 correctly fit the full colour range into the number of colour map entries requested - I don't see why this should be any different for larger colour maps. The work around I'm using is to use pcolor instead of image to plot the data, as this seems to work with a smaller (presumably 256 element) colour map and map the data onto this. While this works, I don't like the pcolor function very much. It's not intended for displaying images. The axes labels align with grid lines instead of pixels, the data cursor selects points instead of pixels, and I need to have an extra row and column of data. Is there a way of getting a 1024 element colour map that behaves as would be expected? Thanks! Richard.	Comment only
04 Nov 2009	Multicore - Parallel processing on multiple cores This package realizes parallel processing on multiple cores/machines.	Karl	Hi Markus, first of all -- you've developed a great tool that helps me a lot with my simulations in the field of audio signal processing. Seeing my dual quad core at 100% (instead of 13%) load warms my heart :). Well, I'm not sure whether I'm getting something wrong here, but I had some problems when the function that is executed by the multicoremaster() (and the slaves) has more than one return value. It seems that in this case all but the first return values get lost. I applied a little trick that I found out about some time ago to solve this problem: Everytime that feval() is called (in startmulticoremaster() and startmulticoreslave() ) I added something like this: N_returnValues = nargout(functionHandleCell{k}); clear('returnValue'); % this is dirty! The next call doesn't work % without clearing "returnValue" beforehand if % N_returnValues==1. If it's greater->no % problem (even without clearing % "returnValue") [returnValue{1:N_returnValues}] = feval(functionHandleCell{k}, parameterCell{k}{:}); % ha! resultCell{k} = returnValue; Doing so, the resultsCell that is returned from startmulticoremaster() is always a cell -- even if the called function has only one return value... I hope this is of any value to anybody and that I'm not causing trouble by posting this hack :). I'm always open to learn a better solution.... Cheers, and thanks again for Multicore! Karl	Comment only
04 Nov 2009	Multicore - Parallel processing on multiple cores This package realizes parallel processing on multiple cores/machines.	Karl		5
28 Oct 2009	real2rgb & colormaps Converts intensity matrices into truecolor images.	Malte	Very handy, worked right away, helped me to superimpose transparent color map on grayscale image. Thanks!	5

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