Paint.NET allows you to use layers and blending modes as the foundation for composing images.
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").
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.
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.
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).
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.
This is the default and standard blend mode. Each pixel in the layer is blended with the composition depending on its alpha value.
Each pixel component's intensity is multiplied with the pixel value in the composition. The result of using this blend mode is always pixels that are darker than the original. White pixels have no effect and are thus effectively transparent.
Each pixel's color intensity is added to the intensity of the pixel values in the composition. This will always brighten pixels in the composition, except for pixels that are completely black which will be effectively transparent.
- Color Burn
- This blend mode has the effect such that dark pixels are made darker. Lighter pixels must be blended with other lighter pixels in order to remain bright.
- Color Dodge
- This can be thought of as the opposite of Color Burn. Lighter pixels are kept light, whereas darker pixels must be blended with other dark pixels in order to remain dark.
- This blend mode can be used for adding shiny objects or areas of light.
This is the reverse of the Reflect mode: it works the same as swapping the layer positions and using Reflect.
This is a combination of Screen and Multiply depending on the intensity of the layer pixel. For darker colors, this acts like Multiply. For lighter colors, this acts like Screen.
The counterpart to Additive. The layer pixel's intensity is subtracted from the composition pixel's intensity resulting in darker colors. Since this can produce a negative intensity, which is not possible to display, the absolute value is used. Thus, both "white minus black" and "black minus white" will both produce white. This is quite often useful when using the Clouds effect.
- At first glance this seems similar to Difference, but it actually produces the opposite effect. Instead of making colors darker, it will make them brighter.
- The lighter pixel of either the layer or the composition is used.
- The darker pixel of either the layer or the composition is used.
"This can be thought of as the opposite of the Multiply blend mode. It is used to make pixels brighter, with black being effectively transparent.
- This is short for "exclusive OR", which is an advanced blending mode that is primarily used for image analysis and not for drawing or image composition.