[Image-SIG] Locate The Center of WhiteDot from a Image

[Narendra Sisodiya]

On Sat, Jan 8, 2011 at 1:44 AM, Christopher Barker <Chris.Barker at noaa.gov>wrote:

> On 1/7/11 10:14 AM, Narendra Sisodiya wrote:
>
>> This Code Look for bounding box which I am calculating by scanning each
>> row and column one by one. If I am finding any white pixel, I am
>> including it into my bounding box.
>>
>
>  1) there may a change that 2 or more WhiteDOT may present. One is Big
>> whiedot and other are very smaller whitedot(just 2-3 pixel) near to this
>> Big whitedot.
>>
>
> Not sure about this one off the top of myhead, but I"d suspect some
> smoothing may take care of it.
>
>
>  I am applying this
>> algorithm on every frame taken from camera at 2fps. So I want a high
>> speed algorithm. PIL must be having some function or trick to do it.
>>
>
> The Image..getbbox() method should do it.
>
>
Thanks, I tried getbbox on wrong image. Now I am using getbbox and I am
getting proper result that too very fast.


> If you need more math, numpy can help. Somethign like:
>
> a = np.asarray(PIL_image)
> background_color = 0
> rows, cols = np.where(a <> background_color) # background color a uint32
> BB = (rows.min(), rows.max(), cols.min(), cols.max())
>


I am unable to get what that code means ?
May you explain how I can use above code with getbbox ? Or the above code
using NumPy is alternate of getbbox method ?
IF yes, then which will be the faster ?

PS: I have looked at centroid algorithm, It is again going at pixel level
and that will be slow. My application will become better with faster
centroid algorithm.


Also I have another question !
I am grabbing image from camera using opencv-python. How we can compare
python PIL with OpenCV ? My guess that PIL will is faster then opencv
library ?
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