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Creating borders?

Jul 14, 2011, 08:34
Post: #1
Creating borders?
Hey everyone, just downloaded Gimp a few days ago and I'm feeling pretty overwhelmed. I'm basically the definition of technologically inept; most the stuff people are talking about in these forums might as well be in a foreign language. Confused

Anywaaay... I'm currently trying to "cut out" pieces of an image. Take this image, for example:
[Image: i-am-rainbow-dash.jpg?w=481&h=276]
All I want is the pony, so that the borders of the image end where the pony's body ends.

Here's something that may be more difficult, but I'm still curious if it's possible. See this image?
[Image: 830px-RainbowDashRainbow.png]
Could I cut out the Pony AND the rainbow with the little sparkles above her? And would it be possible to fuzzy out the lines of the curtain behind the rainbow? If so, then how?

Thanks a bunch for any help! Big Grin
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Jul 14, 2011, 11:20
Post: #2
RE: Creating borders?
In the image has a uniform background, there is a fairly simple and efficient technique expounded here:

This is in case you find other images, because your images above do not lend themselves to it.

Your first image is a JPEG and is full of compression artifacts. You'll have a very hard time getting something out of it. Your best hope is:
- Layer/Transparency/Add alpha channel
- Use the Eraser tool to remove the background. use a very wide brush to remove most of the background, and progressively small brushes as you get close to you subject.
- Take your time. Lots of time. Save the picture in XCF format as your make progress.

Your 2nd image is a lot cleaner since it's a PNG, but forget the stars and rainbow, they are much easier to recreate than to extract (especially since the rainbow is half-transparent)

Method for the Overwhelmed:

- Layer/Transparency/Add alpha channel
- Remove most of the background as above
- Use the magic wand: click on some uniform color area you want to remove, and delete.
- Repeat until happy with result, you can finish up with some eraser.

Much smarter method for the "Moderately Skilled", that takes advantage of the quite uniform pale blue stroke that delineates the character:

- Use Color selection tool (with a rather low threshold, says 5), and Click (and then shift click to fill the gaps) on the contour.
- Save selection to channel (this is a backup, in case you hose it in next steps)
- Grow the selection 1px, then shrink it 1px (this smooths the selection).
- If some stuff gets joined where it shouldn't (for instance the gaps between the hind legs), Ctrl-Click ith the Color selection tool to remove it.
- Save this selection to channel again (you can jettison the previous saved selection)
- Create a new layer, filled with transparency
- Using the bucket-fill tool, in "Fill selection" mode, fill the selection with black. This will create a black contour of the character.
- Change the bucket-fill tool to "fill similar colors", and use it to fill the inside of the contour, until you have a uniformly black silhouette. If you have a spill outside the silhouette, it means there is a gap in your contour. You can close it with a touch up of the paint brush.
- Use eraser/brush to removed small imperfections from the silhouette.
- Check the background for low-intensity selections (appear as gray areas). Erase them (they are easier to spot if you add a temporary white layer below the one you are working on).
- Layer/Transparency/Alpha to selection: this create a selection from the silhouette.
- Feather the selection 1px
- Invert the selection
- Hide the silhouette layer, go back to original
- Delete

Near perfect method for "Those In The Know": use the Paths editor tool and approximate the character with Bezier splines. Then use "Path to selection" and Bob's your uncle.

Absolutely perfect method for "Those Who Have Way Too Much Time On Their Hands And Should Really Be Outside Enjoying The Sun": use the Paths editor tool to recreate the whole character with Bezier splines. It can then be enlarged to any size without loss of quality.

- Layers and Selections for the "Moderately Skilled" method
- Layer and Path for Head extraction for "Those In The Now"

Now answering your questions on
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Jul 15, 2011, 01:55
Post: #3
RE: Creating borders?
Wow thanks! Lots of good info there, think I'll give the "Moderately Skilled" method a try (though don't be surprised if I come running back for extra help!). Also, I've been hearing a lot about "vector art." What is it exactly? Is it possible to do with Gimp? I ask because there are galleries of vector art that feature basically exactly what I'm trying to do.

[Image: young_rainbow_dash_by_atomicgreymon-d3d1u8w.png]
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Jul 15, 2011, 08:13
Post: #4
RE: Creating borders?
Roughly in the computer word there are two kinds of graphics: bitmaps and vector.

In bitmap graphics, you define every pixel of the image. In vector graphics you define "instructions" to draw the image. Computer displays and digital cameras (photo and video) are bitmap devices (which explains the popularity of bitmap-oriented file formats). Flatbed plotters (and very ancient computer graphics displays) are vector devices.

Popular bitmap file formats: JPG, PNG, GIF, BMP, ICO, TIFF

Popular vector file formats: SVG, PS, EPS

Bitmap graphics are difficult to resize properly (especially if the size increases) but are easy to modify locally and can represent very complex images (at the cost of file size) where almost every pixel has a different color.

Vector graphics are easy to scale, and can be quite small even for moderately complex images (computer fonts are vector graphics, for instance). But what limits their use is that in the end they have to be converted to bitmaps for display.

Gimp is designed to handle bitmap graphics, but has some support for vectors (called "Paths" in Gimp). Gimp can also load vector graphics format, either as paths, or as an image (in which case it will ask you how big an image you want the vectors to produce, and at that point you have to take some careful decisions because you can't scale later without losing some sharpness).

Gimp's equivalent for vector graphics is a software called Inkscape.

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