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curving a selection


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Which app & version are you using, & what kind of 'image' are you working with (a pixel, Image, vector, etc. layer)?

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If you create a pixel selection on your image the Mesh Warp Tool will work on that selection only

But your question is still a little vague for me. Screenshots of what you want to do may help

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13 hours ago, jimh12345 said:

I want to select a region in an image (by just dragging a selection rectangle over it) and then "curve" that selected area.

Curving a selection arbitrary afterwards (via handles, like curves with nodes) is AFAIK not directly supported for a plain initial selection. - What you can try instead is ...

  1. add a rectangle shape which covers most of the area you want to cover (you can limit it's layer opacity to better view what to cover), the rect will get it's own layer
  2. now convert that rect shape to curves (Cmd-/Ctrl-Enter)
  3. Use the Node tool to add (if needed for the way you want to curve) and bend nodes as you need and had in mind for curving
  4. Use "Select -> Selection from Layer" to get a selection out of the manipulated curve
  5. Reuse that selection for your main or other layer(s)

... as you can see there are multiple steps needed in order to get something like a curved selection out of a rect.

Further and dependent on which app and tools you use, in APh one can also enhance, add/remove to selection parts, so starting with a rectangular selection and then enhancing adding sel areas to that selection, for example with the brush selection tool ... etc.

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14 hours ago, jimh12345 said:

I want to select a region in an image (by just dragging a selection rectangle over it) and then "curve" that selected area.

Use one of the quick shapes, the Rectangle. Draw it where you want it and then use Layer > Convert to Curves. Now you can use the Node tool to mess about with the shape. Finally use the Select > Selection from Layer to make your selection.

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15 hours ago, jimh12345 said:

How can I "curve" a [rectangular] selection, without creating any other distortions?

If you only distort the selected region and nothing else, you’ll get an overlap where the boundary curves into the adjacent region that you’re curving towards, and you’ll get a gap where the boundary curves away from the adjacent region on the opposite side. Is that really what you want, or have I misunderstood something?

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5 hours ago, Old Bruce said:

Use one of the quick shapes, the Rectangle. Draw it where you want it and then use Layer > Convert to Curves. Now you can use the Node tool to mess about with the shape. Finally use the Select > Selection from Layer to make your selection.

6 hours ago, v_kyr said:
  • add a rectangle shape which covers most of the area you want to cover (you can limit it's layer opacity to better view what to cover), the rect will get it's own layer
  • now convert that rect shape to curves (Cmd-/Ctrl-Enter)
  • Use the Node tool to add (if needed for the way you want to curve) and bend nodes as you need and had in mind for curving
  • Use "Select -> Selection from Layer" to get a selection out of the manipulated curve
  • Reuse that selection for your main or other layer(s)

Yawn, just a repetition of what has already been said one posting before and thus unnecessarily wasted space & energy!

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Thanks all, unfortunately these methods are beyond my expertise with AP and involve too many elements I know nothing about - like rectangle "shapes",  "node tool",  "selection from layer" etc.  I'm just a photographer, not a designer, and would have to move quite a ways up the AP learning curve.   

I tried this method, but quickly encountered things I didn't understand.  I can drag out a Rectangle, I see a Convert to Curves button on the toolbar..  then I find the Node tool and see that I can deform the Rectangle... but that only affects the rectangle itself, not my pixel layer... I don't get how they're supposed to be connected....

 

So I've put this aside for now.

 

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You'll need to make the selection, copy it and paste it. Now you have a layer with only the pixels which form the area you want to curve.

Now use the Mesh warp tool on that copied and pasted layer.

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I have never mastered color management, period, so I cannot help with that.

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2 hours ago, jimh12345 said:

I want to curve the pixel layer (the monitor in your example)

How about one of the Distort (Live) Filters, e.g. Spherical:

448052400_distortspherical.thumb.jpg.d00b331410d6af690247f6ba060b65d2.jpg

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16 hours ago, jimh12345 said:

But I want to curve the pixel layer (the monitor in your example), not delete pixels from it.

Ah, I think I misread your original post.

As I read it now, it now sounds like you know how to make the selection but you want to be able to “curve” the selected area (presumably copying the selected area and then creating a new layer from that, which is then modified).

Is that correct?

If so, there are various ways to “curve” something so we need to know what you mean by “curve” before we can give you better answers than earlier – Mesh Warp as already mentioned, various Filters, Liquify functionalities, etc.

Any visual examples you can give would probably be useful.

P.S. It would be good if you can also explain what you mean by “without creating any other distortions”.

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Attached is the thing I'm trying to 'curve'.  It's a section of a beaded chain (for a jewelry ad).   I've already cut it out from the background and isolated it on a layer.   

The Mesh Tool is a good suggestion, I didn't realize I could use that on the specific pixel region in a layer.  And with it, I can 'sort of' get what I want: a smoothly curved chain.  I say "sort of" because the Mesh tool is working on the entire rectangular region bounding the chain, and when I try to curve the chain it wants to distort the size and shape of the round beads, in non-linear ways.   By fiddling with all the grab handles I can get "close" to a nice result.

What I'd really like to be able to do is draw some sort of a line right down the middle of that chain,  curve the line, and have all the pixel contents follow it.   Hope that makes sense.

The Mesh tool might be "good enough" for what I need to do.  In the second image you can see that I'm close, after a lot of fiddling, but some of the beads are weird.

 

chain.jpg

warped beads.jpg

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8 minutes ago, jimh12345 said:

What I'd really like to be able to do is draw some sort of a line right down the middle of that chain,  curve the line, and have all the pixel contents follow it.

It sounds as though you want to create an Image Brush.

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jimh12345: Because you are manipulating pixels – tiny squares of colour – and not a real-world item, you are bound to get “distortions” where the software has to ‘guess’ what to do with those pixels where they are ‘squashed’, ‘stretched’ or ‘missing’.

(Also the beads in your original chain are not in a perfect line so that’s not going to help matters when you are trying to add a curve to it.)

Alfred’s suggestion of using a brush is probably the nearest you will get to what you want but you may find that the result isn’t realistic as the lighting on each bead will be rotated with the path of the brush, rather than it being applied to the chain as a whole.

You could try creating a bead without much lighting on it, creating and using a brush from that, and then applying some kind of lighting effect afterwards but, since the chain will be ‘flat’ – it’s just 2D with no depth information – I don’t think that will produce very good results unless you are prepared to add lighting to every bead manually, and very carefully.

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It doesn't have to be perfect, just good enough.   I decided the difficulty came in because the Mesh tool is working on a bounding rectangle, and the 'handles' aren't in the best places.

So I came up with a clever workaround.  I isolated the chain on a layer, rotated it to be vertical, and cropped around it,  assuming the Mesh tool would then work on a bounding rectangle closely matching the object.

But the Mesh tool "remembers" the original orientation and persists in using it.  I even tried saving the layer as a new file and reopening it - no luck.   Useless, and IMHO weird, behavior - see attached image:
 

straight chain.jpg

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17 minutes ago, jimh12345 said:

But the Mesh tool "remembers" the original orientation and persists in using it.

Try Rasterise & Trim before you use the mesh warp

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18 hours ago, jimh12345 said:

What I'd really like to be able to do is draw some sort of a line right down the middle of that chain,  curve the line, and have all the pixel contents follow it.   Hope that makes sense.

What lets you avoid creating an image texture brush, as recommend before by @Alfred?

1001551809_chain3asbrush.thumb.jpg.bdaac796ba1b1ee363d40fd3e783c3de.jpg

18 hours ago, jimh12345 said:

The Mesh tool might be "good enough" for what I need to do.  In the second image you can see that I'm close, after a lot of fiddling, but some of the beads are weird.

Just in case: you can add nodes to the mesh and thus prevent sections from being modified and drag others separately.

789264299_chain2.thumb.jpg.58a191aa66dfadfefb177bbfaff1b7da.jpg

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  • 2 weeks later...

I think the mesh tool will do what I want, although the need has passed - couldn't figure this out in time so a simpler image was used.

My takeaway from this is a familiar one:  get it right - the way you want- in the camera, instead of fiddling endlessly in post-processing. 

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