More Background Manipulation with the GIMP

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Foreground Select

Deus Nefum's picture

Why not just use the foreground select tool?

Quick Mask Tip

MacAnthony's picture

When you are in quick mask mode, you don't have to change to the erase tool to remove the mask. If you look at an alpha channel mask, you see that the mask is black and the unmasked area is white. You can just keep using the pen tool but switch the foreground and background color between black and white to add/remove the mask. Black with "paint" more mask and white will erase the mask.


Mitch Frazier's picture

I noticed something "strange" happening when I was doing one of my video "takes" and I had the foreground/background colors swapped, but... I didn't take time to figure it out.

So thanks for the tip, I only hope I'll remember it the next time I need it :).

Mitch Frazier is an Associate Editor for Linux Journal.

A more appropriate way to

cbleslie's picture

A more appropriate way to accomplish the action of extracting "Chilli Dog" from his/her background would to have been to use a Layer Mask, thus making the editing "non-destructive" should you ever have to go back and fix a transparency mistake 7 hours down the road into a project.

Layer Mask

Mitch Frazier's picture

As I've stated before: I'm no gimp expert, or for that matter an expert in any sort of photo manipulation program. So tips are always welcome and if you'd like to contribute a video of your own let me know.

Mitch Frazier is an Associate Editor for Linux Journal.

I just may.... :)

cbleslie's picture

I just may.... :)

Please do

Mitch Frazier's picture

We're always looking for contributors, particularly for videos.

Mitch Frazier is an Associate Editor for Linux Journal.

feather and transparent

lefty.crupps's picture

I find it better to use some 'feathering' when selecting these types of images, to help soften the edges of the subject (chilli dog in this example). Then when removing the background, the subject has softer edges.

If you then save the image with a transparent background (png files have this, gimp files have it, but jpegs do not), you don't have any of the slightly-blue borders.

Nice tutorial, that QuickMask button is new to me!

More Info Please

Mitch Frazier's picture

I know in theory what you're referring to and I think I've accidentally stumbled across it when cutting out images, but I've never been able to figure out exactly how I got there. So a bit more info on how to do this would be nice.

Mitch Frazier is an Associate Editor for Linux Journal.

Feathered edges

lefty.crupps's picture

> So a bit more info on how to do this would be nice.

In the Gimp, once you've chosen a Selection tool (such as the Lasso/Free Select that you picked), the bottom half of the toolbox changes to that tool's options.

Click the box []Feathered Edges and then you can adjust its radius, which is basically the distance from your line that will become slowly faded from fully opaque to fully transparent. This will help the image appear to blend in better with the background. I do not know how this works in conjunction with the Quick Mask thing, that should be tested a bit.

Note, if you then paste this onto a blue background (or whatever) for later use as you suggested, your fade will have some blue in it which pretty much ruins the effect. Much better to then save it as a file format that allows transparency (such as PNG), and just keep the background empty (transparent).


Cycron's picture

Yes, you could have done color select, you just hold down shift when you're doing it so you can select more than one color. And I would have changes the lighting a bit in the photo so the dog would fit in with the rest of the photo. and I would have had the background color as transparent, not blue, because if its blue then (as you can see) there is a little blue lining around the dog when you paste him in.


Mitch Frazier's picture

That's a good point. I have a bit of a phobia about "transparency" I think. Every time I have an image with transparency something seems to not work like I think it should. But, remember I'm no gimp expert so I'm 100% sure it's just my lack of knowledge about the gimp that is causing me problems.

Mitch Frazier is an Associate Editor for Linux Journal.

Very funny!

Mauricio.Mora's picture

Thanks Mitch!
Very funny and basic for Gimp, right?

Basic Once You Know It

Mitch Frazier's picture

It's fairly basic stuff I guess but if you're new to the gimp or only use it occasionally some of these things are far from obvious. I'm an occasional gimp user and I've only recently discovered these "basic" things.

Mitch Frazier is an Associate Editor for Linux Journal.

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