Every layer has a name. This is assigned automatically when the layer is created, but you can change it. You can change the name of a layer either by double-clicking on it in the Layers dialog, or by right-clicking there, and then selecting the top entry in the menu that appears, Edit Layer Attributes.

An alpha channel encodes information about how transparent a layer is at each pixel. It is visible in the Channels dialog: white is complete opacity, black is complete transparency and gray levels are partial transparencies.

The background layer is special. If you have just created a new image, it only has one layer, which is the background layer. If the image has been created with an opaque Fill type, this one layer has no Alpha channel. To get a background layer with transparency, either create your new image with a transparent Fill type, or you use the Add an Alpha Channel command.

If you add a new layer, even with an opaque Fill type, an Alpha channel is automatically added to the layer.

Every layer other than the bottom layer of an image automatically has an Alpha channel, but you can't see a grayscale representation of the alpha values. See Alpha in Glossary for more information.

Alfa kanalo pavyzdys. 

Pav. 8.2. Alfa kanalo pavyzdys: elementarus paveikslėlis

The image on the left has three layers painted with pure 100% opaque Red, Green, and Blue. In the Channels dialog, you can see that an Alpha channel has been added. It is white because the image is not transparent since there is at least one 100% opaque layer. The current layer is the red one: since it is painted with pure red, there is no green and no blue and the corresponding channels are black.

Pav. 8.3. Alfa kanalo pavyzdys: vienas permatomas sluoksnis

The left part of the first layer has been made transparent (via Skyrius 2.2, „Rectangle Selection“, then Edit → Clear). The second layer, green, is visible. The Alpha channel is still white, since there is an opaque layer in this part of the image.

Pav. 8.4. Alfa kanalo pavyzdys: du permatomi sluoksniai

Kairioji antrojo sluoksnio dalis buvo padaryta permatoma. Trečiasis sluoksnis, mėlynasis, yra matomas pro pirmąjį ir antrąjį sluoksnius. Alfa kanalas vis dar yra baltas, kadangi šioje paveikslėlio dalyje yra nepermatomas sluoksnis.

Pav. 8.5. Alfa kanalo pavyzdys: trys permatomi sluoksniai

The left part of the third layer has been cleared. The Alpha channel is still white and the left part of the layer is opaque, because the background layer has no Alpha channel. In this case, the Clear command works like the Eraser and uses the Background color of Toolbox.

Pav. 8.6. Alfa kanalo pavyzdys: alfa kanalas pridėtas sluoksniui

We used the Layer → Transparency → Add Alpha Channel command, on the Background layer. Now, the left part of the image is fully transparent and has the color of the page where the image is shown. The left part of the Alpha Channel thumbnail is black (transparent) in the Channels dialog.

The layer type is determined by the image type (see previous section), and the presence or absence of an alpha channel. These are the possible layer types:

The main reason this matters is that some filters (in the Filters menu) only accept a subset of layer types, and appear disabled in the menu if the active layer does not have a supported type. Often you can rectify this either by changing the mode of the image, or by adding or removing an alpha channel.

It is possible to remove a layer from an image, without destroying it, by clicking on the symbol in the Layers dialog. This is called „toggling the visibility“ of the layer. Most operations on an image treat toggled-off layers as if they did not exist. When you work with images containing many layers, with varying opacity, you often can get a better picture of the contents of the layer you want to work on by hiding some of the other layers.

	Patarimas
	Jeigu laikydami paspaudę klavišą Shift spustelėsite akies simbolį, visi sluoksniai išskyrus spustelėtąjį bus paslėpti.

Usually, you activate a layer, to work on it, clicking it in the layer list. When you have a lot of layers, finding which layer an element of the image belongs to is not easy: then, press Alt and click with Mouse wheel on this element to activate its layer. The available layers will be looped through (starting from the upper one) while the Alt is held and the picked layer will be temporarily displayed in the status bar.

If you click to the right of the eye icon, you can select the lock settings for the layer.

Directly to the left of the image thumbnail, you will see the Layer Effects icon if that layer has effects added to it.

In GIMP, the boundaries of a layer do not necessarily match the boundaries of the image that contains it. When you create text, for example, each text item belongs to its own separate layer, and the layer size is automatically adjusted to contain the text and nothing more. Also, when you create a new layer using cut-and-paste, the new layer is sized just large enough to contain the pasted item. In the image window, the boundaries of the currently active layer are shown outlined with a black-and-yellow dashed line.

The main reason why this matters is that you cannot do anything to a layer outside of its boundaries, unless you enabled Expand Layers in the Paint Tool Options. If this causes you problems, you can alter the dimensions of the layer using any of several commands that you can find near the bottom of the Layer menu.

	Pastaba
	Sluoksnio naudojamos atminties dydis priklauso nuo jo matmenų, ne nuo jo turinio. Taigi, jeigu dirbate su dideliais paveikslėliais arba paveikslėliais, kuriuose yra daug sluoksnių, gali būti naudinga apkirpti sluoksnius iki mažiausio galimo dydžio.

Sluoksnio nepermatomumas nurodo kiek yra matomos žemiau esančių sluoksnių spalvos. Nepermatomumas gali būti nuo 0 iki 100, 0 – visiškas permatomumas, o 100 – visiškas nepermatomumas.

Sluoksnio veiksena nurodo kiek sluoksnio spalvų yra kombinuojama su žemiau esančių sluoksnių spalvomis, norint gauti matomą rezultatą. Tai yra gana sudėtinga, ir pakankamai svarbu, kad šiam principui būtų skirta atskira sekcija, žr. Skyrius 2, „Sluoksnių veiksenos“.

Be alfa kanalo yra dar ir kitas būdas valdyti sluoksnio permatomumą: pridedant sluoksnio kaukę, kuri yra papildoma pilkų atspalvių piešimo sritis, susieta su sluoksniu. Pagal numatytuosius parametrus sluoksnis neturi sluoksnio kaukės: ją reikia pridėti atskirai. Kas yra sluoksnių kaukės ir kaip jas naudoti yra aprašyta sekcijoje Sluoksnio kaukė.