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Thread: Selection without alpha

  1. #1
    Join Date
    Feb 2012
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    Selection without alpha

    Hi there

    I would like to have selection without alpha.

    In this case you would select around the painted area discarding alpha information.


    Thanks Mic

  2. #2
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    I'm not quite sure what you mean when you say 'discarding alpha information' - Selection sets themselves ignore alpha but if you're talking about copying the contents of a selection set do you mean that you want the contents copied to include all visible layers (including the canvas), or that you want the copy to only include the contents of the layer itself? If you could explain the intended effect of what you're asking for I should be able to understand a bit better.

  3. #3
    Join Date
    Feb 2012
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    Hi Matt

    Let say I have a watercolor blob (of any size) on a layer. Since it is watercolor there will be alpha information in the blob.

    Here is the equivalent of what I want with to many operations:

    1. Select layer content

    2. Invert the selection

    3. Make a new layer

    4. Fill selection on new layer with paint bucket (This layer only)

    5. Make stencil from layer content

    6. Invert the stencil


    I now have a mask around the blob with no alpha information inside the hole.


    It would be much faster to have "Select layer content without alpha" (featherd)

    Hope it is clearer

    Thanks

    Mic
    Last edited by Micmac; 03-18-2016 at 10:57 PM.

  4. #4
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    Not sure I follow your steps: When you create a selection from the layer contents, the alpha of those contents is included. So if your watercolour blob is less than 100% opaque in its center (which is likely) then your selection has alpha in it. The selection outline may not display this because the outline is generated where the edge hits at least 50% opacity (I think it's 50%, anyway) but there is alpha in there.

    Try this:

    1. Paint a watercolour blob.
    2. Select layer contents.
    3. Add a new layer and hide your watercolour layer.
    4. On the new layer, paint using the oil brush. Note that the colour fades towards the center of the blob.

    In step 4, the colour fades because your selection is not 100% opaque.

    The problem with the request is that there is no technical difference between the empty space outside the area of your blob and the partially empty space inside it other than the fact that outside, it's 0 alpha, and inside it's above 0. Select Layer Contents selects all pixels that are above 0 alpha, but the selection reflects their internal alpha to maintain antialiasing and feathering. There's no way to turn than in to a selection that ignores the alpha inside the blob while maintaining the antialiasing on the outside of the blob as there's no actual difference between those pixels.

    If you could explain what you're trying to achieve by doing this I might be able to help.

  5. #5
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    Feb 2012
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    Quote Originally Posted by MattRage View Post
    If you could explain what you're trying to achieve by doing this I might be able to help.
    I wat to be able to paint inside selections (disregarding the alpha) with the full color that I have selected.

    Mic

  6. #6
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    Magic Wand selector does this, spread and feather set to 0, antialiasing off and current layer only selected (just in case you have stuff on other layers that overlap it).

    Make Blob
    Click Blob with Magic Wand Selector setup
    Make New Layer
    Hide Previous layer
    Paint selection in with whatever you like

    No invert selections, masking, or anything needed. Hope that I am understanding what you are looking for properly.

  7. #7
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    Sorry, no it doesn't

    Mic

  8. #8
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    Yeah that's odd as it seemed to do exactly what you were describing. Is there another program with a similar effect that I could reference so I could understand what you are looking for.

  9. #9
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    Alright, I think I understand now what you are looking to do. It is to make a selection of everything on a layer that has any alpha information and then remove the transparency information of those pixels. It works with the magic wand, but not for really complex subjects or many disconnected objects.

    This would be an excellent addition for selections, but may be much better to allow this to be coupled with a selection by range tool attached to the magic wand. That would allow for more than just alphas then, you could have it check for specific hue, luminance, saturation, or paint depth ranges to allow for selections that are extremely versatile and could be used in conjunction with the additive, subtractive, difference, intersect, replace options to create incredibly complex selections for applying changes to only very specific areas of an image. Those would allow for things we simply cannot do at all in the current version of the software.

  10. #10
    Join Date
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    Quote Originally Posted by Micmac View Post
    I wat to be able to paint inside selections (disregarding the alpha) with the full color that I have selected.

    Mic
    Ah, so basically, the reverse of transparency lock?

    You should be able to do something like this by using the Magic Wand to select the *empty* spaces, or by creating your selection on the layer beneath the current paint, and painting under the existing paint.

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