[Date Index]
[Thread Index]
[Author Index]
Re: Circular neighborhood for ImageApply
*To*: mathgroup at smc.vnet.net
*Subject*: [mg115064] Re: Circular neighborhood for ImageApply
*From*: Shadi Ashnai <shadi at wolfram.com>
*Date*: Thu, 30 Dec 2010 04:09:40 -0500 (EST)
Hi Adrian,
In ImageFilter you cannot specify a non-rectangular neighborhood yet. The following code would only count the zero pixels inside the disk and divide by the size of the disk:
disksize = Total[DiskMatrix[r], 2];
ImageFilter[Count[DiskMatrix[r] - #, 1., 2]/disksize &, ColorConvert[i, "Grayscale"], r]
Another suggestion would be to remove disks smaller than your radius by doing:
Closing[i, DiskMatrix[6]]
If you got Mathematica 8, you can simply compute the center of each foreground object (remaining disks) by either of the following:
1) MaxDetect[ DistanceTransform[ image ] ] (* computes the ultimate erosion and returns an image consisting of the centers *)
2) ComponentMeasurements[ image, "Centroid" ] (* returns the coordinate of the centers *)
Best,
Shadi Ashnai
Wolfram Research Inc.
From: "Adrian Boyko" <adrianboyko at gmail.com>
To: mathgroup at smc.vnet.net
Sent: Tuesday, December 28, 2010 5:52:36 AM
Subject: [mg115064] [mg115022] Circular neighborhood for ImageApply
Usual disclaimer: I'm a casual home user of Mathematica, so please
forgive what might seem like silly questions.
I'm using ImageFilter like this:
ImageFilter[1.0*Count[Flatten[#], 0.]/Length[Flatten[#]] &,
ColorConvert[binaryImage, "Grayscale"], r]
I.e. I'm trying to replace each pixel with the ratio of 0 pixels and 1
pixels in its square neighborhood. I'm doing this because I'm trying to
find the center of disks (of an expected radius) in a scanned image, and
this works reasonably well. But, since I'm actually looking for disks I
think it would be better to find the ratio in the pixel's _disk_ (not
square) neighborhood. It seems like there ought to be a simple way to
work DiskMatrix[3] into my expression, and extra processing time isn't
an issue.
Any ideas? Is there some operator I can apply to # and DiskMatrix[3]
which would mask out the neighborhood values outside the disk? I think
ImageMultiply ought to work like an ImageAnd if all my pixel values are
0 or 1, but I haven't had any luck with it.
On a tangent, I have another filter that ought to be looking for the
ratio in a ring neighborhood between r1 and r2. Maybe the answer to my
first question will also tell me how to combine DiskMatrix[r1] and
DiskMatrix[r2] to get RingMatrix[r1,r2].
Any help will be greatly appreciated.
Thanks,
Adrian
P.S. I'm considering the upgrade to Mathematica 8. Since I have a
CUDA-compatible graphics card, is it safe to assume that version 8 will
_automatically_ utilize it when executing these sorts of operations? Or
would I need to code differently to take advantage of it?
Prev by Date:
**Re: About TeXForm**
Next by Date:
**Re: typesetting problems or bugs? need a professional**
Previous by thread:
**Circular neighborhood for ImageApply**
Next by thread:
**Re: Wolfram does not support Mathematica 8.0 on SUN OS**
| |