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cut, floating selection, align

Oct 21, 2012, 20:07
Post: #1
cut, floating selection, align

I have simple problem which is making me mad.
I have 2-colour image (white background and green GreenObject in ObjectImage).
I want to paste green object into another gimp file (MainImage) as a layer, additionally I want to use Alignment Tool to align it.

1) I'm changing white to transparent in ObjectImage.
2) Selection->All
3) Selection->Float
4) Copy from ObjectImage
5) Paste into MainImage
Here is my first frustration -> why Floating Selection has size of ObjectImage not my GreenObject ?? (I don't want unnecessary border). Anyway, I can work-around it doing Alpha to Selection and Layer->Crop to Selection.
And now is second one - how to use Alignment Tool ?? Until I have Floating Selection layer the tool is unavailable (everything greyed-out). After anchoring I can't easily select my GreenObject. I can do again Crop to Selection and Select All and then the tool will work. Anyway - what is the easiest way of using Alignment Tool with object cut by Floating Selection ?? What actually Layer->Crop to Selection does ?? (does it change layer size, or maybe just selecting some subarea of layer ?? Is it at all possible to have layers of different sizes ?? How to set relative offsets between them then ??)

I have as well third frustration - I have 2-colour image (255, 255, 255) and (151, 202, 77). Why when I use Colours/Colour to Alpha with white colour the green one is becoming semi-tranparent (106, 107, 0) ?? (I want it to be solid)

I use GIMP 2.8 on Linux

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Nov 3, 2012, 12:30
Post: #2
RE: cut, floating selection, align

Thank you for your reply. Finally I finished graphic I was working on using Inkscape purely in vector graphic. However I like GIMP and I like to understand how things work.

(Oct 21, 2012 23:49)ofnuts Wrote:  What else do you expect after "Select/All"? (btw "Select/Float" is unecessary).

I was expecting that new layer size will be clipped to the floating selection, which is happening eg. when I will do 1) eclipse selection 2) shrink selection 3) copy 4) paste as new layer.
If I understand correctly now floating selection is more like pixel mask rather then selection (which is subpart of image), is that correct ??

(Oct 21, 2012 23:49)ofnuts Wrote:  The alignment tool aligns layers (actually, layer borders or layer centers)... Buttons are grayed as long as you haven't selected at least one layer (by clicking on it, which adds 4 small squares in its corners). This tools is not often used because very often instead of aligning layers with regards to each other one aligns them all along a "guide". It's a bit more useful in "distribute" mode.

Of course for all practical purposes this assumes that these layers are smaller than the canvas. "Layer/Crop to selection" indeed reduces the layer to whatever is in the selection and this usually makes it smaller than the canvas. Its opposite is "Layer/Layer to canvas size". You can easily reduce a layer to the minimum size required by its non-transparent pixels using "Layer/Autocrop layer". To set relative offsets between layers you just move them around using the Move tool (quirk: by default it moves the topmost layer which isn't transparent where you click to start the drag).

That is good one, I understand layers now better. Before was using few layers each size of the whole picture. Now I use much more small layers and align them to each other.

(Oct 21, 2012 23:49)ofnuts Wrote:  The goal of "Color-to-alpha" is to produce a layer, which, when put above a layer filled with the removed color, gives exactly the same image. Unfortunately, there is not a unique solution to this: on white, a light green could be a completely opaque light green or a partially transparent dark green, and C2A choses the transparent version, which is the right thing to do... because you can prevent this to happen. C2A works on the pixels in the selection, so you can select the background (Wand tool), "Select/Grow" to make it include your border pixels (those must become semi-transparent), and then apply C2A (which won't apply to the inside of your object) See the "background removal" link in my sig for the full story.

This is not very intuitive, but it's good to understand it.

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