Using layers in GIMP for postwork.
I'm trying to get my head around this. I have two layers in GIMP, the bottom layer is JPG, the top layer is PNG (which enables it to have transparency I think). I want to make the top layer semi tranparant. Apparently the way to do this is to go to Layer>transparancy>Add alpha channel and then alter the opacity. At least that's what several google searches have led me to be believe. However when I go to the transparancy part, the Add alpha channel option is greyed out I can't select it. Can anyone help me as I know quite a few people on here use GIMP for postwork?
I am reallty losing my patience with ****ing GIMP!
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Do you actually have the layer as a layer or is it still just pasted in/temporary?
If you use 'Paste as' > New Layer it will paste it in as an actual layer.
What layout are you using and version of GIMP? (it would be easier if I could see some screenshots, too...) Because the way GIMP is there's a million ways to get to, see and use the various tools/panes/etc...and it would be nice to know if you and I are on the same page.
A jpg doesn't have an alpha layer by default, so if you drop it into Gimp, and then erase an area, it will fill that erased part with your background colour. On the other hand a PNG already has an alpha layer attached by default, which is why it is grayed out. You can't add it because it is already there. So unlike your JPG layer, when you erase some of the PNG, you will then see the layer that is underneath it.
Now when you say you want to make it semi-transparent, do you want to make the entire layer semi transparent, or just parts of it. If you want to make the entire layer semi transparent, then all you need to do is lower the opacity slider in the layers panel. (you don't need an alpha channel to perform this step) If you just want an area to be transparent, then you need to add a mask. Right click on the layer and select add layer mask. Make sure that the mask is selected. You can switch between the layer and the mask by selecting each of their icons in the layers panel. (the mask should be selected by default) If the mask is selected. Everything that you paint black in the mask will be fully transparent in the layer, white is not transparent at all, and greys are in-between.
I didn't paste a layer in, I just went on Open As Layer and selected my PNG image, so that puts it on top of my JPG image as far as I know. Ok, I understand "A jpg doesn't have an alpha layer by default, so if you drop it into Gimp, and then erase an area, it will fill that erased part with your background colour. On the other hand a PNG already has an alpha layer attached by default, which is why it is grayed out. You can't add it because it is already there. So unlike your JPG layer, when you erase some of the PNG, you will then see the layer that is underneath it. " that. Cool. At the moment I want to make the entire PNG layer transparent (no point making things more tricky for myself just yet!). So I click on Layer>Transparency? On that it gives me a bunch of options about alpha channels, but nowhere can I see the word Opacity. apart from in the Tools box, which doesn't seem to do anything to the layer itself.
You set it in the layers panel: (In the image, Opacity is highlighted in orange.) Just click the up down arrows, or drag the slider to adjust. Just a side note, Gimp usually has all the panels and layers floating around your screen everywhere. If so, you may find it helpful to set it to single window mode: windows > Single window mode. This keeps all the panels neatly organised in one window. I find it much easier to use that way.
Ah, there it is! Thanks! It works! I would have thought it would have been logical to find it going to layers>tranparency and so on, but GIMP had other ideas! Another quick question. I have some PNGs I want to add as a semi-transparent layer which I now know how to do (thanks again). But is there a way to alter the PNG layer's colour (for example, a black splash of paint changed to red to simulate blood)?
Just another side note- above opacity slider there is a drop down box for mode: I don't know how much you know about blending modes, but you should definitely get to know these. you will use them so much for post work. This determines how the layer interacts with the layers beneath it. So, for example, if you have a character with two lights attached- A rim light and a side light.
You can render them out as two separate images:
(Image 1) Just the rim light
(Image 2) Just the side light.
Drop them into gimp and select "screen" blending mode for the top layer. This combines the lighting from both images: (Image 3) This is pretty much what it would look like if you rendered the image with both lights on in the first place. The difference is now, because they are two separate layers, I can fine tune each ot them.
Eg In (image 4) I kept the side light at the same intensity, but made the rim light a little brighter. You see how powerful this can be?
I think it's because you use it so often, they decided to put it somewhere that is easy to see and get to.
It depends on what your image looks like. Is it just a pure black splotch on a transparent background? If so, there are many ways you can do this.
1) Change your foreground colour to red.
In the layers panel, right click on the layer itself (In the above image that would be the white square next to the word background) and select Alpha to selection. This will select everything that isn't transparent.
go into edit > fill with FG colour
or
2) Go into colour > Hue Sautration.
drag up the lightness slider, so that the image isn't pure black.
move the hue slider until you get the colour you want
play with the saturation until you have the right intensity.
EDIT*
Once you have your blood, change the blending mode to overlay. That will make the blood blend in nicely with the skin
Yes, it's a simple black splotch. Method 1 worked fine. Here is a quick example. Another question (yes, I know I'm a pest!), is it possible to move the splotch layer, so the blood goes on a different part of the face? Or alter the size of the splotch?
Thanks for your help. You've proved that GIMP can work well, but only if someone who knows what they're doing walks you through how to do stuff.
No problem at all. Glad to help out. I know how frustrating it can be trying to find your way around these programs.
To move the layer, Select the move tool- see the image below. In the tool options select "Move the active layer" then you just left click the image and move it.
To alter the size- select the resize tool. click on the image and it draws a cage around the image. just click the corners of the cage and drag. There is an option to constrain proportions if you need it
Thanks for that. You should write a manual for GIMP, as your instructions have been the clearest I've come across! Although that would probably take you a very long time!