[Courses][gimp] Lesson 6: Erasing Unwanted Objects from Images

Julie Sloan juliesloan at mindspring.com
Sat Mar 5 14:37:49 EST 2005


I thought the plastic wading pool and the miniature windmill detracted from 
the sunflowers.  This is simply amazing.  :)

I also removed the guy wires and a big weed from my rose bushes.



On Friday 04 March 2005 03:14 pm, Akkana Peck wrote:
> One of the best uses for an image editing program is to erase
> things you wish weren't in the picture.  Maybe you have a great
> photo of your sweetie except there's a telephone pole growing out of
> his head; maybe that outhouse in the background really takes away from
> your nice scenery photo.  For whatever reason, learning to remove
> stuff from images is a fun and important gimpish skill.
> Removing objects undetectably can be very difficult.  I'll touch
> on several techniques you can use for simple removals.  For difficult
> projects involving complicated backgrounds, it will usually take a
> combination of several tools, plus lots of patience.
> Let's start with this hummingbird image:
> http://shallowsky.com/images/gimpcourse/lesson6/hummer-orig.jpg
> Isn't that branch annoying?  The one going straight through her head?
> And that other branch that's blocking our view of her?
> Let's explore some techniques for removing them.
> An easy tool to start with is the Smudge tool.  It looks like a hand
> with a pointing finger.  Smudge does exactly what the name implies: it
> behaves as though you were smudging or smearing the image with your
> finger.  Select it in the toolbox, and look at the tool options.
> Notice that the smudge tool has a Brush associated with it.  The brush
> you choose makes a big difference.  Most of the time, you'll probably
> want a fairly large brush, with a fuzzy edge, not a sharp edge.
> But for very small images, you may want to use a small brush, or
> even one with sharp edges.  I'm going to choose "Circle Fuzzy (15)",
> the third-from-largest fuzzy circle.
> Now I'm going to try to smudge out that small branch under the bird's
> bill.  The smudge tool will drag color from wherever I start, onto
> where I drag.  So I'm going to drag from the bright area, onto the
> branch.  Smudging only works over a short distance (the color "runs
> out" after a little while); so I have to smudge repeatedly, many
> times, to get rid of the branch.  I go back and forth, sometimes
> dragging from below the branch upward, sometimes from above downward.
> Remember, you can always zoom in to get a better view of the part of
> the image where you're working.  Hitting = or + a couple of times
> can help you see what you're doing.
> Digression: Zooming in is useful, but if you have a small image,
> sometimes it makes it hard to see how the image looks at its native
> size.  Here's a nifty GIMP trick: multiple views of the same image!
> Choose the first item in the View menu, New View.  This opens a new
> window showing the exact same image as the original window.  Then you
> can make one big and one small; do your painting and smudging on the
> big window, and look at the small one to see the result of your work.
> Back to smudging: you're doing lots and lots of little motions, each
> one of which is an action as far as Undo is concerned.  So you probably
> won't be able to Undo a whole smudging session, though you can always
> undo the last few bits of it.  Be sure to save your work before you
> start smudging, and if you decide smudging wasn't the right thing, you
> can use "File->Revert" to go back to the image before you started.
> Here's what it looks like partway in:
> http://shallowsky.com/images/gimpcourse/lesson6/hummer-somesmudge.jpg
> and all the way:
> http://shallowsky.com/images/gimpcourse/lesson6/hummer-smudged.jpg
> The Clone tool iss similar to smudge, but more powerful.  Clone
> "remembers" a source region which you choose; then, as you paint in
> the image, instead of painting a fixed color, Clone will copy from
> that source image.  The icon in the toolbox looks like a rubber stamp,
> and the tooltip says "Paint using Patterns or Image Regions".
> I'm going to go after that vertical branch that's blocking some of
> our view of the hummingbird.  I can't use the smudge tool for that,
> because her breast and wing have feather patterns, and smudging
> will spoil that and will end up looking artificial.  But if
> I can copy the feather patterns from her breast, I might be able to
> use them to paint over that branch.  I'll use a slightly smaller brush
> than I used with the smudge tool, Circle Fuzzy (13), because I don't
> want to slop over and get white breast-feather pattern painted over
> the bird's wing or head.
> The clone tool has to be initialized before you can paint with it.
> At first, when the clone tool is selected, when you move your mouse
> into the image, the mouse cursor will show a circle-slash, meaning
> "You can't paint anything yet!"  Select a source region with
> ctrl-click: move the mouse where you want your source region, hold
> down control, and click the left mouse button.  Do this as close as
> possible to the piece you want to remove, so that the color and
> pattern will be right.  But you can't get too close, or else, when you
> paint with the clone tool, part of the source pattern you're painting
> will be exactly the part you want to remove!
> Once you've ctrl-clicked, the mouse cursor should no longer show that
> circle-slash.  You're ready to paint!  Do so, in very small strokes,
> just like you did with the smudge tool earlier.  You may find that
> you have to paint a small area, then select a new source image
> (ctrl-click again) because the color changes.  For instance, my
> hummingbird is light colored where the sun is hitting her, but has a
> shadowed portion down near the branch she's sitting on.  I'll need
> to paint those two areas separately, with different source regions.
> Here she is with the parts in front of her removed with the clone tool:
> http://shallowsky.com/images/gimpcourse/lesson6/hummer-clone.jpg
> I could go on using Clone and Smudge to paint out the rest of the
> branch, but I have a shortcut for the next step: I'm going to select
> a region next to the branch that's the same shape as the branch, then
> paste it on top of the branch.  If that doesn't make sense, bear with
> me while I follow the steps:
> First, I'll use a selection tool to select the part of the branch
> still above the bird.  Regardless of which tool I use, I want the
> selection "feathered", which means that the edges of the selection
> will be fuzzy, not sharp.  Sharp lines in selections tend to stand out
> when you paste them somewhere else.  All of the selection tools have a
> "feather" option in the Tool Options dialog, where you can set how
> fuzzy you want the edges to be.
> I'm going to use the lasso ("free select") tool, which lets me
> hand-draw the outline of the branch.  It's not critical that the
> outline exactly follow the branch; the important thing is that my
> selection is entirely outside the branch, and that it's in the right
> place in places where the branch touches the bird or the branch above
> it.  Here's a screenshot of my selection:
> http://shallowsky.com/images/gimpcourse/lesson6/hummer-branchselect.jpg
> Now I have the branch (and a little padding around it) selected.
> But what I actually want is to copy something right next to the
> branch, not the branch itself.  I can get that by moving the selection
> over by approximately the width of the branch.
> It would be nice if I could just click in the selection and drag it,
> but that moves the contents of the selection, leaving a blank white
> area behind it.  (Try it!  It's undoable.)
> In gimp, alt-drag moves a selection.  That sounds straightforward --
> except that in most Linux window managers, alt-drag is already claimed
> as "move window".  So when you alt-drag the selection, most likely,
> the whole gimp image window moves.  Not what you want!
> (Try it.  If it moves the selection, then be happy! and ignore
> the next paragraph.)
> There are two ways around this.  First, you can configure your window
> manager not to use alt-drag to move windows.  This is supposedly the
> recommended approach, but I don't recommend it; it means you'll have
> to do this on every window manager you ever use, and if you ever try
> to show a friend how to do something, it won't work for them.
> Fortunately, there's another way: alt-shift-drag also moves the
> selection.  Here's where I've moved the selection:
> http://shallowsky.com/images/gimpcourse/lesson6/hummer-selectmoved.jpg
> Now I Copy, then Paste, as in Lesson 4.  The pasted piece shows up as
> a new layer in the layers dialog, and I can Move it using the move
> tool (while it's a floating selection, I can also move it just by
> dragging it).  It's a bit hard to see the how well the edges match
> while I'm doing this, so I temporarily turn the marching ants off with
> View->Show Selection, or ctrl-T.  (Don't forget to turn them back on
> again afterward.)
> When I'm happy with the placement of the new layer, I need to merge it
> with the base layer.  Why?  Because I have some extra cruft at the
> edge of the pasted layer, plus some extra stuff next to the
> hummingbird's head, which I'll need to clean up with Clone or Smudge.
> Tools only work on one layer at a time, and I'm going to want to be
> able to smudge or clone right across the boundary of the layer I just
> pasted.
> To merge the selection layer into the background layer, I go
> to the Layers dialog, and instead of clicking the New Layer button
> as we've done in past lessons, I click the Anchor button.
> http://shallowsky.com/images/gimpcourse/lesson6/hummer-pasted.jpg
> Now I Smudge to clean up the area above the hummer's head.  I'll also
> use the Clone tool to get rid of the bottom part of the branch.
> Here's the result!
> http://shallowsky.com/images/gimpcourse/lesson6/hummer-final.jpg
> I'm done!  No more annoying branches in the way.
> Homework: Erase something out of an image, using whatever tools seem
> most appropriate.
> Next Lesson: Advanced selection, with paths; and enhancing just the
> selected part of an image.
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