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Adjusting an overall image color?

Discussion in 'General GIMP help' started by Whirler, Dec 28, 2012.

  1. Whirler

    Whirler Member

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    Haha. Don't know why I didn't think of selecting the white and inverting selection, as I've been doing that very thing while building the rivers layers for each area. But thanks for pointing it out. 4% cutting it a little close, no? LOL Thanks for hanging in there and answering first. :)
     
  2. Whirler

    Whirler Member

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    I just discovered something interesting. When I have a river, which is typically a lot of thready winding segments that vary in shades of a color, on a layer by themselves, and I have already taken the white background of this River layer to Alpha in a previous session, it can get tricky to re-select all the pixels of the river to edit the color when desired. But, if I zoom in far enough in GIMP on this River layer, the Alpha background switches to being all white. THEN, I can select by color on the white background, invert the selection, and have all the pixels of the river coloration selected to brush over them with whatever color I choose. :)
     
  3. ofnuts

    ofnuts Member

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    It is much better to do an "alpha to selection" on that layer. The problem of the color selection and fuzzy selection is that the selected pixels are always fully selected. There is no partial selection, so all effects/painting are fully applied to the pixels and there is no blending to the rest on the border of the selection, so things end up blocky/jagged/pixellated.
     
  4. Whirler

    Whirler Member

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    I just experimented with a river I have on an alpha layer and read the tool tip description that opened for selecting "alpha to selection" which says "replace the selection with the layer's alpha channel". Please correct me if I am wrong, but it appears that function would be meant to REMOVE the "selected" river from the layer? That's not what I was wanting to do. What I just posted had allowed me to select all of the river pixels, which would be nigh impossible any other way as they are different shades of color.
     
  5. ofnuts

    ofnuts Member

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    No, it just creates a selection mask from your alpha channel, so that partly transparent pixels are partly selected, and typically you'll use this selection on some other layer. In this image:

    [​IMG]

    • The top line is a text entered with the Text tool
    • For the middle one: Alpha-to-selection on text layer, add layer, bucket-fill selection
    • For the bottom one: Color-to-selection on text layer, add layer, bucket-fill selection

    The blockiness of the bottom one is due to partially transparent pixels (anti-aliasing pixels) that become fully selected in the color-selection while they are partially selected in the alpha selection. So in one case they are fully painted, and in the other they are made only partially opaque, by the selection amount, so the bucket-fill reproduces exactly the original layer.
     
  6. Whirler

    Whirler Member

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    Interesting. I'll keep this in mind. Thanks! This seems to touch on something I noticed today but was not quite sure about. When I have, say, 3 layers in an image, and I have something selected from one of the layers, does the selection remain usable on ALL the layers at the same time? Like I can select an area on the bottom layer, move to the top layer, and fill the same selection?
     
  7. ofnuts

    ofnuts Member

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    Yes... the selection is a mask which is the size of the image, not of specific layer, and has the scope of the image (it's not specific to some layer). When you paint/transform the affected pixels are those of the active layer intersected with the selection (there are cases where the selection has no intersection with a given layer, in which case nothing happens...).

    And yes, very many Gimp techniques use one layer to obtain a selection, then use that selection on another layer.
     
  8. Whirler

    Whirler Member

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    Thanks. I'm going to try to research the Fuzzy Selection tool to see if I can set constraints on just how 'fuzzy' it can get, and whether I can tell it not to select beyond a defined size perimeter away from where I clicked. It's definitely a handy tool, but as mentioned earlier, has some caveats.
     
  9. ofnuts

    ofnuts Member

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    You can intersect selections, for instance: define a rough area with freehand selection, save it to a channel ("Select/Save to channel") then use the Fuzzy Select, then go to the Channel list, right click on the channel with the saved freehand selection and "Intersect with selection" so that the fuzzy selection is now restricted to the pixels that were also in the freehand selection.

    You can also intersect "on the fly" by using the Ctrl-Shift combo on the second selection, but in case of mishap you have to redo both selections.

    Fuzzy-select and Color-select are evil... they don't do what beginners expect them to do. They should have been made unlockable by sufficient Gimp XP.
     
  10. Arzoroc

    Arzoroc Moderator Staff Member

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    What ofnuts said, or you change the threshold in the tool settings. This doesn't give you a "border" but it's still customizing the tool a bit.
     
  11. Whirler

    Whirler Member

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    Thanks! What is currently working for me is the ability to expand or reduce the fuzzy selected area by moving the mouse immediately (and I do mean immediately!) the instant the mouse button is clicked on the target color, although the interface is backwards from an intuitive point of view. Drag UP to decrease????

    Is there any way to increase the amount of time this operation looks at mouse movement after the click? It works well, but I often have to repeat the attempt 2 or 3 times to actually get it to respond, because it seems to only look for movement within the first few fractions of a second, after which it ignores movement, no matter how long I hold the mouse button. My motor reflexes aren't what they used to be. :) In addition to that, if I do hold the mouse button "too long" (I very much hate any and all time-sensitive control interfaces!!!) which is to say more than 0.68 seconds, GIMP will start the blue spinning windows cursor of death which almost certainly leads to it having "stopped responding" and requiring forced closure (often losing work done just prior).

    Last night's session was very unstable. GIMP pretty much stopped responding every time I closed the current project window, and then attempted to close the blank image window that always remains at the end, over a period of 4 hours. It seems to need some polishing, stability-wise.
     
  12. Whirler

    Whirler Member

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    Thanks! What is currently working for me is the ability to expand or reduce the fuzzy selected area by moving the mouse immediately (and I do mean immediately!) the instant the mouse button is clicked on the target color, although the interface is backwards from an intuitive point of view. Drag UP to decrease????

    Is there any way to increase the amount of time this operation looks at mouse movement after the click? It works well, but I often have to repeat the attempt 2 or 3 times to actually get it to respond, because it seems to only look for movement within the first few fractions of a second, after which it ignores movement, no matter how long I hold the mouse button. My motor reflexes aren't what they used to be. :) In addition to that, if I do hold the mouse button "too long" (I very much hate any and all time-sensitive control interfaces!!!) which is to say more than 0.68 seconds, GIMP will start the blue spinning windows cursor of death which almost certainly leads to it having "stopped responding" and requiring forced closure (often losing work done just prior).

    Last night's session was very unstable. GIMP pretty much stopped responding every time I closed the current project window, and then attempted to close the blank image window that always remains at the end, over a period of 4 hours. It seems to need some polishing, stability-wise.
     
  13. ofnuts

    ofnuts Member

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    Just do Ctrl-Z and your last added selection is removed.

    If you work with complex selections, learn to use "Select/Save to channel", for simple-minded backup/restore or for more complex operations. This will make your life a lot easier and a lot less stressful.
     
  14. Whirler

    Whirler Member

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    Yes, CTRL+Z has been my friend in all of this, together with upping the default number of undo levels from 4 to 12. ;) But a bit larger window of mouse movement response time would lessen my need for using it while employing the fuzzy tool. :)

    I've yet to learn the first thing about channels. With a program this complex, I find it best to learn the tools as I need them. Trying to read the manual for this program before first use would be literally impossible, and nothing would be retained. I'll research channels next and see how they can help. Thanks!
     
  15. Whirler

    Whirler Member

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    I'm not sure what you meant by the last sentence, but any time a programmer gives a user FULL control over turning options and default settings on and off I am most adamantly in favor of it! :)

    So I just tried your suggestion here, about intersecting a fuzzy selection with a channel-saved freehand selection, and it works great! In fact, I can see this as a major help in trying to constrain the fuzzy tool just to areas I want. In this case, I wanted to select the water, but not the boats and structure, of a harbor along the shore of a bay. It would be maddeningly detailed work to try to do so by tracing, and without the channel constraint of loosely tracing the harbor, the fuzzy tool wanted to select the whole bay area, because coloring here is very common throughout. I could not get moving the mouse with the fuzzy tool to help. But it was child's play with the technique you described. Thanks very much!

    One of the trade-offs in my undertaking is to decide just how detailed I want to get. When it comes down to thousands of tiny little docks and piers jammed together in a postage stamp sized harbor of a city, I have typically passed them by when doing the water masking for FSX scenery and just left the static bitmap image coloration in them provided by the satellite image. But with this technique, it would be pretty easy to actually include all these marinas during the water masking stage, where I would be tracing the shoreline. So in the end, FSX would render water there, complete with its transparency, wave effects from blowing wind, etc. making them look far more realistic. -=
     

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