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Edge detection

New Here ,
Jul 30, 2020 Jul 30, 2020

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Does anyone know if PS has an edge detection capability.  I have an image of an old barn in a field and would like to detect its edges then reduce the opacity and print it as a shadow and then ink sketch the edges on the print.

 

Much appreciated, 

 

Doug

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Community Expert ,
Jul 30, 2020 Jul 30, 2020

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Hi Doug,

 

Yes! It does, but the tool you would use depends on the photo. Can you post a screenshot of the image? What version of Photoshop are you using? 

Michelle

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New Here ,
Jul 30, 2020 Jul 30, 2020

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Michelle - not on my computer that has the image, but using the latest PS

 

Doug

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Community Expert ,
Jul 30, 2020 Jul 30, 2020

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Thanks Doug! I think Conrad's post has exactly what you are looking for. 

 

Let us know if that works or if you have any other questions!

Michelle

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Community Expert ,
Jul 30, 2020 Jul 30, 2020

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Photoshop has many tools along those lines, it depends a lot on how distinct the edge of the barn is. Some of the tools look for edges by contrast, some them by content, and the newest ones detect edges by content, aided by machine learning. Sometimes you have to try more than one of the tools to see which one works best in a specific case.

 

The new Select > Subject command can often recognize a dominant subject and draw a selection for it in one step. Or at least, a selection that’s close enough that it’s easy to clean up. In the current version of Photoshop, Select > Subject is the best place to start.

 

The next best tool to try is the Object Selection tool, which is like a more directed form of Select Subject. Draw the Object Selection tool roughly around the barn, and it will figure out that just the barn outline needs to be selected. If the default rectangular mode of the Object Selection tool does not produce an accurate enough selection, the Lasso mode of the Object Selection tool is more precise because you can draw it more closely around irregular edges. The Object Selection tool in Lasso mode is shown below.

 

Object-Selection-barn-shadow.gif

 

The Quick Selection tool and Magnetic Lasso tool are “semi-automatic,” If you drag the Quick Selection tool inside the edge you want, it can often figure out what the rest of the edge should be. If you drag the Magnetic Lasso along the edge you want, it can often follow that edge. Both have override modes so if they get it wrong, you can teach them where the real edge is.

 

The Lasso tool and Pen tools can also be used, but they are the most manual methods that take the most time.

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Community Expert ,
Jul 30, 2020 Jul 30, 2020

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Filter > Stylize > Find Edges.

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Community Expert ,
Jul 30, 2020 Jul 30, 2020

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Not to mention Filter > Filter Gallery > Stylize > Glowing Edges

 

Or the various edge detection algorithms such as Laplacian, Roberts, Prewitt, Robinson, Sobel, Kirsch, Scharr – which can be generated using Filter > Other > Custom

 

https://www.dropbox.com/s/yvzlr1fuznyf8iw/Custom%20Convolution%20Kernels.atn?dl=0

 

(I created this Custom Convolution Kernels.atn file back in 2008, however it should still work... it was more for a learning exercise than anything)

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Community Expert ,
Jul 30, 2020 Jul 30, 2020

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For sketcking edges there is a filter find edges you mat find handy.

image.png

image.png.

JJMack

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New Here ,
Jul 31, 2020 Jul 31, 2020

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Thanks a bunch guys, will give it a go.

 

Cheers,

 

Doug

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