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Layers and Blend Modes

Paint.NET allows you to use layers and blending modes as the foundation for composing images.

Layers

For this discussion the following two images will be used for the background layer and for the 1st layer that is placed on top of the background layer:

Background Layer - Picture of a Classic Camaro
("Bottom Layer")

Layer 1 - Picture of Seattle
("Top Layer")

You may think of "layers" as a stack of transparency slides that, when viewed together, form a complete image. Paint.NET displays this stack as if you were viewing it from the top and with no perspective (layers do not get "smaller" when they are closer to the bottom of the stack, which would place them "farther away"). To better visualize how layers work, it may help if we view the layer stack from the side instead of from the top:

Pixels and Transparency

Every layer in Paint.NET is composed of pixels which are stored in the RGBA format. The RGB part stands for red-green-blue, and is used to store traditional color intensity. The "A" is for alpha and is used to store information about the transparency of a pixel. This alpha value may range from 0 (completely transparent) to 255 (completely opaque). (Other software may refer to this as ranging from 0% to 100%.) If a pixel is transparent, then pixels from the layers below will show through. Paint.NET uses a technique called alpha compositing to be able to display a layered image on a standard computer monitor.

However, transparent pixels cannot be displayed on a computer monitor. In order to simulate this Paint.NET uses a checkerboard pattern, which looks like this:

If you see this then it means that part of your image is transparent -- the checkerboard pattern is not actually part of the image. You may think of the checkerboard pattern as a virtual background layer, or "layer zero," which is always below all layers that are shown in the Layers window. However, as previously mentioned, it is not actually part of the image. If you save the image and then view or load it with other software then the checkerboard pattern will not be there (unless, of course, if that other software also uses a checkerboard pattern to simulate transparency).

Layers and Opacity

While every pixel has transparency information associated with it, every layer also has an associated opacity value. The two terms are similar and in most cases can be treated as the same. You may think of a layer's opacity value as a "dimmer" for the alpha values of every pixel in the layer.

For example, if we take the top layer and adjust its opacity from 255 gradually down to 0, we will get the following images, shown as both conceptual stacks and as it would be shown on the computer monitor:

Layer 1 at 255 opacity (100%)
Completely opaque: The car is not visible.

Layer 1 at 128 opacity (about 50%)
Partially transparent: The picture of Seattle is partially visible.

Layer 1 at 0 opacity (0%)
Completely transparent: The picture of Seattle is not visible.

Blend Modes

A layer's blend mode specifies how it is blended with the layers below it. To change a layer's blend mode, click on the respective layer and then open its Properties (via the Layers menu, the Properties button, or by double clicking the layer). The following dialog will be shown:

Not all blend modes are easy to understand in classic or intuitive terms, and because of this we recommend that you experiment and make use of the forum for asking questions and getting tips. Each blend mode is described below along with an image composed of the two layers discussed previously, but with the respective blend mode selected and the opacity set to 255.

In the discussions below, the term composition will be used. This refers to the result of blending all of the layers below the current layer which is being discussed. The "final" composition is what you see on the screen while working with the image. However, for this discussion we need to refer to the composition as it is being composed, layer by layer.



Copyright © 2007 Rick Brewster, Tom Jackson, and past contributors. Portions Copyright © 2007 Microsoft Corporation. All Rights Reserved.