| Re: finding boundary in image having multiple region of interest [message #93590 is a reply to message #93589] |
Wed, 31 August 2016 02:37   |
Helder Marchetto
Messages: 520
Registered: November 2011
|
Senior Member |
|
|
Hi,
I can't tell if what you did is correct or not, but if you want to convert one-dimensional subscript to two dimensional, then array_indices is the way to go.
For some examples, to learn how to use it, have a look at the help pages:
http://www.harrisgeospatial.com/docs/ARRAY_INDICES.html
I also think that the label_region page has an example on how to use the reverse_indices of the histogram function to retrieve one-dimensional subscripts:
http://www.harrisgeospatial.com/docs/LABEL_REGION.html
I think the last line of the example is the most important one:
img[r[r[i]:r[i+1]-1]]
The histogram function help page also has some more info on how to use the reverse indices:
http://www.harrisgeospatial.com/docs/histogram.html
Good luck,
Helder
On Wednesday, August 31, 2016 at 8:21:46 AM UTC+2, sin wrote:
> On Tuesday, August 30, 2016 at 2:22:18 PM UTC+5:30, Helder wrote:
>> On Tuesday, August 30, 2016 at 8:07:48 AM UTC+2, sin wrote:
>>> Hi all,
>>> I need to select roi having combined pixel area above 3493pixels and intensity above 1.25.
>>>
>>> I tried using find_boundary which gives the pixel area for pixels above the threshold for one roi that we give as input. But in one image I have multiple rois to be selected. so find_boundary will not work.
>>>
>>> I have several images like this.
>>>
>>> So do anyone have any idea to do this.
>>>
>>> The threshold should be the intensity should be more than 1.25 and the combined pixel area should be greater than 3493 pixels.
>>>
>>> thanks
>>
>> Hi,
>> I don't understand why you tried find boundary. But I think what you're looking for is a combination of "greater then" and label_region.
>>
>> subImage = myImage gt 1.25
>> lr = label_region(subImage)
>>
>> then use histogram to identify the regions and look for the one's with more than 3493 pixels. In case of doubt, follow the example given for label_region:
>> http://www.harrisgeospatial.com/docs/LABEL_REGION.html
>>
>> Here is what is of interest for you:
>>
>> h = histogram(lr, REVERSE_INDICES=r)
>>
>> ; Print the mean and standard deviation of each region
>> FOR i=0, N_ELEMENTS(h)-1 DO if h[i] gt 3493 then $
>> PRINT, 'This region ', i, ', has a population greater than 3493 and has = ', h[i], $
>> ', elements. The indices of this region are between ', r[i],' and ', r[i+1]-1
>>
>> I hope this helps.
>>
>> Cheers,
>> Helder
>
> Thanks a lot helder, it is very helpful.
> But I couldnt understand how to get array x,y coordinates from the indices r(i).
> can i use array_indices for this purpose.
> I tried but i am not sure whether it is correct or not.
>
> thanks
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
