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Author Topic: selecting a large area of metallic grid  (Read 1220 times)
wlong
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« on: March 11, 2009, 12:40:07 AM »
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I wonder if someone could please help me ?  

I have a large area of metal with holes in it and I want to select the holes in order to remove the area (smoothly) so that I can place a different sky.  I have tried a variety of techniques which have all failed.  So I'm presently selecting each hole separately, with the magic wand tooll which I found works leaving the smoothest line.   I have tried selecting the entire metal sheet and then inverting the selection, but I end up with a very jagged edge.  As this is going to take me a very long time doing it this way, I have plenty of time to try different techniques  

Does anyone have any solution or hints please ?

Thanks in advance
« Last Edit: March 11, 2009, 12:42:22 AM by wlong » Logged

KSkewes
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« Reply #1 on: March 11, 2009, 08:34:51 AM »
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Quote from: wlong
I have a large area of metal with holes in it and I want to select the holes in order to remove the area (smoothly) so that I can place a different sky.  I have tried a variety of techniques which have all failed.  So I'm presently selecting each hole separately, with the magic wand tooll which I found works leaving the smoothest line.   I have tried selecting the entire metal sheet and then inverting the selection, but I end up with a very jagged edge.  As this is going to take me a very long time doing it this way, I have plenty of time to try different techniques  

I assume there is a least some decent difference in luminosity or colour saturation between the grid and background. If this is the case may I suggest you use a channel luminosity mask. The process for doing is is as follows:
1. Create a new empty layer and put this at the bottom of the stack
2.  Making sure your main image layer is selected bring up the channels pane and view each individual colour channel (make sure your prefs give you a monochrome representation of them)
3. Select the channel which has the greatest contrast between the metal and the sky
4. Load this channel as a selection (by press the buttom at the bottom of the pane which is a circle of lines)
5. With the selection still active create a layer mask on the main image (the selection should automatically load into the mask)
7. Alt-click on the mask to view it, then using levels or curves on the mask to make it higher contrast (making the grid white and the sky black, if the sky is brighter then the grid in the first instance simply inert (apple-i) the mask)
6. Refine the masked area using the brush and lasso tools
7. Place your new sky in the empty layer at the bottom of the stack.    

Hope this technique works for you.

     
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Eyeball
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« Reply #2 on: March 11, 2009, 09:13:31 AM »
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This is a case where posting the image, even a downsized one, would be extremely helpful in understanding your situation and offering suggestions.  There are many ways to create a mask and without seeing an example, everyone will just be guessing as to whether the method will work efficiently for you or not in this case.  There are many free hosting sites available if you want to do that.  pixentral.com is one.
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