Revision Date: 15 January 2023

Working with Layers

Paint.NET uses "layers" to form a composite image. Imagine these layers are a stack of transparent slides. Each slide can contain a separate element which forms part of the overall image.

Paint.NET displays the stack of layers as if it was viewed from above. Thus, the order of the layers as shown in the Layers Window is important. Opaque pixels on a layer higher up the stack will obscure pixels contained in layers lower in the stack.

If this image were viewed in Paint.NET the image would look like this

The Active Layer

There is always one active layer. It can be identified by the highlighting in the Layers Window (the layer named "Apple: Foreground" in the image above is the active layer).  Drawing operations are only applied to the active layer. No other layer will be affected.

It is easy to shift the active layer status from one layer to another. Simply click on any layer's name in the Layers Window to apply the active layer status to that layer.  The active layer will be shown highlighted in the Layers Window (blue highlighting in the image below).

Only one layer may have the active layer status at any time.

The Active Layer + Opacity

Layers can have their own opacity setting. Opacity is applied to every pixel in the layer, so it acts like layer-wide transparency setting.

To adjust a layer's Opacity setting, highlight the layer in the Layers Window (see above - the Active Layer) and press the F4 key.  The layer Properties dialog will open.

Opacity or Alpha values range from 0 (completely transparent) to 255 (completely opaque).  To change the value, click and drag the slider control or type a new value into the numerical value box.

A demonstration of layer opacity can be seen below (Layers and Opacity).

The Active Layer + Blend Modes

Layers can have their own blend mode. The blend mode dictates how the layer is merged with lower layers when the image is composed.

Like Opacity, Blend Modes are applied to every pixel in the layer.

To change a layer's Blend Mode, highlight the layer in the Layers Window (see above - the Active Layer) and press F4.  The layer Properties dialog will open.

A new Blend Mode can be selected from the drop-down list. Click on a new Blend Mode to apply it to the layer.

The Active Layer + Visibility

Layers can have their visibility toggled on and off. There is a checkbox beside each layer in the Layers Window which controls the layer visibility.

If the checkbox is ticked ☑, the layer is visible and will be included in the composite image when it is assembled.  If checkbox is unticked ☐, the layer will not be visible and will be excluded from the composite image.

A layer which is not visible still forms a part of the image when it is saved in the *.PDN format.

To change a layer's visibility, click the checkbox beside the layer in the Layers Window. This checkbox is also available in the Layer Properties dialog (press F4 to show the active layer's properties).

Layer Order

The order which layers appear in the Layers Window is important. Layers higher in the list or stack will obscure layers lower in the stack (unless the higher layer has some transparent regions when the lower layer(s) will show through).

Layers can be moved by highlighting them in the Layers Window and using the up or down icons at the foot of the Layers Window.  Alternatively, click and drag the layer to a new position in the Layers Window.

Pixels and Transparency

Each layer in a Paint.NET image is composed of pixels. Pixels contain both a color and an alpha, or opacity, value.  Paint.NET uses a technique called alpha compositing to display a layered image on a standard computer monitor.

In Paint.NET, Alpha values range from 0 (completely transparent) to 255 (completely opaque). Other software may refer to this range using 0% through to 100% but the idea is the same.

If a pixel is transparent or partially transparent, then pixels from layers lower in the stack will show through to some degree.

As transparent pixels cannot be displayed on a computer monitor, Paint.NET uses a gray and white checkerboard pattern to give a visual clue to transparency.

When this pattern is seen, it indicates that this part of the image is transparent.

For the following discussion, these two images will be used.

Layers and Opacity

In addition to the transparency information (Alpha value) associated with each pixel, each layer also has an associated opacity value.  Consider a layer's opacity setting as an additional Alpha amount applied to all the pixels in the layer.