| ## Layers Layers is a concept that allows for a lot of flexibility in image creation and manipulation. In short: layers allow the image to consist of multiple individual layers that can be painted and manipulated independently of each other. A layer can be thought of as a transparent slide that shows through what is underneath it except for the parts that are fully covered with paint. Only one layer can be active at a time. This means that painting operations affect only one layer. Some image-processing operations affect all layers no matter what layer is actually active. The layers in ArtPaint have the following features: Layers can be added or deleted Layers can be reordered Layers can be merged Support for unlimited number of layers Layers can be hidden Layers can be duplicated Currently most of the painting that can be done to a layer is replacement painting. This means that whatever color was in the layer gets replaced by the new color when it is being painted. This means that in order to get a semi-transparent part in the image multiple layers must be used. ### The Layer-window The place where the layers can be controlled is the layer-window, which is pictured in figure 1.
Figure 1: The layer-window.
The layer window displays layers for the currently active paint-window (or the window that was last active). At the top of the window is a thumbnail of the image. Below that is area for layers. Each layer has its own rectangle-shaped entry in that area. The active layer is marked with darker grey background and a blue rectangle around the thumbnail-image. On the left side of the layer's area is the thumbnail-image of that layer's contents. You can drag this image to a paint-window to copy the layer there. On the right side is a checkbox for controlling whether the layer should be visible or not. By pressing primary mouse-button in the grey area and dragging up or down the layers can be reordered. By pressing secondary mouse-button over the grey area you can bring up a pop-up-menu for controlling the layer operations (it can be brought up also by pressing the primary mouse-button while holding down a modifier-key on the keyboard). Figure 2 shows this menu.
Figure 2: Layer pop-up-menu.
The menu-items "Merge With Front Layer" and "Merge With Back Layer" merge the layer with its neighbor. Merging means that the two layers are removed from the image and replaced with just one layer. Front layer means the layer that is upper in the list and back layer means the layer that is lower in the list. "Add Layer In Front" and "Add Layer Behind" add a new layer behind or in front of the layer where the button was pressed in. "Duplicate Layer" duplicates the layer where the mouse-button was pressed in. "Delete Layer" removes the layer from the image.