Edge detection

[Doug B.]

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

[mglush]

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

[Doug B.]

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

Doug

[mglush]

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

[Conrad_C]

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.

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.

[Semaphoric]

Filter > Stylize > Find Edges.

[jenhintz]

Can anyone tell me if theres a function like this for the ipad or web versions of photoshop? Currently those are my only options, old desktop can't support photoshop. 

[Conrad_C]

Not currently. The web and mobile Photoshop apps offer only a small fraction of the full desktop Photoshop feature set. Adobe is adding desktop features to the mobile versions over time, but it is not clear when specific features, such as certain filters, will be available on the web/mobile versions.

Some feature require a total redesign to work within web/mobile constraints, such as a touch interface.

[Stephen Marsh]

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)

[JJMack]

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

.

[Doug B.]

Thanks a bunch guys, will give it a go.

Cheers,

Doug