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ostinelli
ostinelli
Participant
October 7, 2017
Question

Remove small selections

  • October 7, 2017
  • 2 replies
  • 2359 views

Dear all,

I have a satellite image and I'm trying to find a way to select all forest areas. I wish there was a tool such a "pattern matching" selection tool that would allow me to select a small forest area and search for all similar areas in the whole image. Kind of a reverse content-aware fill. Unless I'm mistaken, there's unfortunately not such a tool.

Therefore, I'm using the magic wand to select the non-tree areas (such as grass fields) so that I can then invert the selection and that would be my forests.

The magic wand tool works great to select these areas, however (as expected) there are small selections (a lot of them) in the trees as well.

What I'd need would be to remove from a magic wand selection all of the selections that are smaller than, say, 5 pixels, and keep only the "big" areas. This would hopefully give me a selection of fields and hence - my forests.

A manual selection would really be my last possible option, it's a really big area with a _lot_ of discontinuity between forest areas and grass areas.

Any inputs / ideas are warmly welcome.

Best,

r.

      2 replies

      Martin_Bns
      Martin_Bns
      Inspiring
      October 7, 2017

      Hi Ostinelli,

      The selection are based on a lot of factor and one of these is CONTRAST.
      There is no artificial intelligence inside Photoshop which can determine which are of the image you like to select or not.

      Said this, you can create some curves adjustments in order to add more contrast to the image and help Photoshop to "see" which areas you are interested in. For example when you are going to use the Color Range feature, you can set with a slider the overall area you'd like to select.

      As KKMack told you, I think the only possible solution is to listen to you favorite playlist and do the hard job with the lasso tool but in order to help you better, it'd be nice to see the image and understand, if there is any way to speed up the process.

      Regards,
      Martin

      ostinelli
      ostinelliAuthor
      Participant
      October 7, 2017

      Thank you Martin,

      it does look like my favourite playlist might be the way to go. As per your request, here's an excerpt of the image:

      Sat - Album on Imgur

      Dave I did try that. Selections just disappear.

      JJMAck

      JJMack
      Community Expert
      JJMackCommunity Expert
      Community Expert
      October 7, 2017

      If you use the magic wand and get the selection you want but it has a bunch  of little area you want included or exclude you can switch to the lasso tool and hold the shift key or alt key down and the lasso those areas to add or remove them from the selection you have.

      JJMack
      ostinelli
      ostinelliAuthor
      Participant
      October 7, 2017

      Thank you JJMack,

      Yes but that again would require a lot of manual work. Isn't there some way by contracting/expanding /refining borders to eliminate the small selections? I've tried quite some ideas but I have yet to be successful in my tries.

      davescm
      Community Expert
      davescmCommunity Expert
      Community Expert
      October 7, 2017

      Have you tried Select > Modify > Contract 3 pixels followed by Select >Modify > Expand 3 pixels. That should remove very small selections although would lead to some corner rounding on the main areas

      Dave

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