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Need help with an effect, not sure what to call it

Apr 21, 2014, 19:42
Post: #1
Need help with an effect, not sure what to call it
Hi all, first post here. I've been quite successful over the last couple years using gimp and haven't needed any help but now I'm stuck. The best way I can describe it is I want to take a RGB photo and convert it to black and alpha. Not so much the grey scale where it has several shades of grey but rather where the image is made up of just black and clear. I'm making a project where I will be applying this over a background color. Here's a couple examples of work I've found online. I don't want these images just the same effect.
[Image: 300722_234436270034846_1212631623_n_zps2252e8f1.jpg]
[Image: RC-Custom-Lab-Workz-Transmitter-Hydro-Di...4685c3.jpg]
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Apr 22, 2014, 08:08
Post: #2
RE: Need help with an effect, not sure what to call it
Assuming that your example no.2 is referring to the skulls pattern and not just advertising Wink

Several ways and all depends on the image. As Ofnuts post it might be just separating the foreground from the background.

This is another way and I am sure there will be more ways to come.

screenshot http://i.imgur.com/PQVwRBX.jpg

The steps in this one
A bit of pre-processing to remove a shadow and then some scaling.
reduced the number of colours to 6
applied the threshold tool to make a black/white image.
color-to-alpha to remove the white.


screenshot http://i.imgur.com/pHzWiFc.jpg
Then the result copied to the clipboard and used as a pattern.
For something like the skulls, use it as a brush (stamp) with maybe a dynamics applies if you want random.
Export as a brush or a pattern to use in the future.

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Apr 22, 2014, 13:33
Post: #3
RE: Need help with an effect, not sure what to call it
haha yes no advertising just a picture I found. I was doing the threshold adjustment but it only worked on perfectly contrasted and lighted objects. If the top were slightly darker in the original it didnt work at all.
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Apr 22, 2014, 14:06
Post: #4
RE: Need help with an effect, not sure what to call it
(Apr 22, 2014 13:33)jcarver1112 Wrote:  haha yes no advertising just a picture I found. I was doing the threshold adjustment but it only worked on perfectly contrasted and lighted objects. If the top were slightly darker in the original it didnt work at all.

Yes, you have to consider each image on its own. That is why image specific tutorials tend to disappoint.

Maybe you could post an example somewhere for others to try-out.

I did reduce the colours for the purpose of separation in the threshold tool. If you look at the screenshot each 'colour' is one of the spikes. Threshold slider - one side black, the other side white.
Reducing the colours, I find mode -> indexed then back mode -> rgb gives a better separation than using the posterize filter.

but

lots of ways to get a result.

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Apr 23, 2014, 06:30
Post: #5
RE: Need help with an effect, not sure what to call it
Another way ,
1
First right-click on the image layer in the layers window,
click "add alpha channel"
2.
use Foregroundselect Forground select tool.
http://docs.gimp.org/2.8/en/gimp-tool-fo...elect.html

It's like a smart select tool!
Works great once you learn how it works.
3.
Now, with the tool, mark/click or drag the selection points around your object first. (loosely, like roughly cutting out an object with a pair of scissors, but don't make it too loose)
4.
Then the next step is painting the inside of the selection to refine it more (You're in this tool the whole time.)
- You can adjust the size of the foreground select brush size under it's "Tool Options"
- Paint around the inside of the object, except for any holes, don't worry to much about edges, see "Hold crtl" below...
- Hold ctrl , plus the left-click to erase outside of the selection mask any parts of the background that You don't want on your object. Like the holes & outside edges. It will automatically refine the edges as you paint & (ctrl) erase Smile

Push enter to finalize/create selection, you should now see marching ant/lines around your object.

(for a silhouette,
create a new "transparent" layer,
buckfill with black inside the selection,
turn down the opacity of the layer some to see the holes,
Last, use Ellipseselect to select & delete those holes
*If painting the mask with foreground select selected around the holes, you can maybe skip this step.)

...(If not making a silhouette, continue below)
Then "Select > Invert" to select the background.
Then push delete.

For holes (like the speedometer/meter readouts) simply erase with the Eraser eraser tool or Ellipseselect select with ellipse select & press delete.
*Again, if the foreground select tool selected around the holes, you might be able to skip this step.

------------
I have a similar tutorial with visuals & steps for more complex selections,
consider combining the above posted methods (threshold, etc.) with my fly away hair tutorial (may take a little practice):
http://gimpforums.com/thread-selecting-f...7#pid21197


*if you can provide us with the image, sketch of image/object, or a similar object if not like the ones you first posted
we can test out or offer better suggestions on how to get the effect.

"In order to succeed, your desire for success should be greater than fear of failure." BC
[Image: 29uocaf.png]
iFS007 tut vids on YT ~ auto color B&W landscape tut
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