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Topic: Converting a magnified image of a line to a single pixel smoothed
Replies: 11   Last Post: Apr 26, 2013 4:24 AM

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 Dave Waddell Posts: 4 Registered: 4/17/13
Re: Converting a magnified image of a line to a single pixel smoothed
Posted: Apr 25, 2013 2:51 AM

On 4/20/13 4:41 AM, Dave Waddell wrote:
> I tried converting the result image to a graph so that I could apply a
> moving average and then fit a B-spline through it. As you can tell I'm
> new to Mathematica:
> data = ArrayRules@SparseArray@ImageData[result]
> It was all downhill after that. Another nudge would be appreciated.
> Thanks, Dave.
>
> Dave,
>
> On 4/17/13 1:30 AM, Dave Waddell wrote:

>> I have a magnified image of a 0.1mm line here:
>> http://www.d-a-v-e.org/images/Trace.jpg
>> ... this converts with Binarize very well:
>> http://www.d-a-v-e.org/images/Trace%20binary.jpg
>> ... but what I would like to do is convert it to a single pixel wide

> smoothed line running right up the middle. Any suggestions or pointers
> on how to do this in Mathematica would be appreciated.

>> Dave
>>

>
> The sequence below seems like a good start.
> The documentation for the functions should help you understand what is
> going on in more details:
>
> trace = Import["http://www.d-a-v-e.org/images/Trace.jpg"]
>
> b = ColorNegate@Binarize[trace];
> b2 = SelectComponents[b, "Area", -1];
> b3 = FillingTransform@b2;
> dt = ImageAdjust@DistanceTransform@b3; result =
> ColorNegate@Image[WatershedComponents[dt], "Bit"];
> HighlightImage[trace, result]
>
>
> Matthias Odisio
> Wolfram Research

ImageValuePositions will give you the coordinates of the white pixels:

In[21]:= ImageValuePositions[Image[IdentityMatrix[3], "Bit"], 1]

Out[21]= {{0.5, 2.5}, {1.5, 1.5}, {2.5, 0.5}}

Please note that ImageValuePositions does not sort the returned positions in
any specific order.

Matthias

So I think I'm really close:
resultOut = ImageValuePositions[Image[WatershedComponents[dt], "Bit"], 0]
BSplineFunction[MovingAverage[resultOut, 5]]
ParametricPlot[%170[x], {x, -8, 8}]

... but I feel I could do much better and make it smoother. All suggestions
are much appreciated.
Dave

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