Layers & Compositing

OxieDraw composites your artwork from a stack of layers, on the GPU.

The layer stack

• Layers - raster layers you paint on, plus text layers.
• Folders / groups - organise layers; a folder is a real composite scope, so effects can be clipped to it.
• Blend mode and opacity - set per layer to control how it combines with the layers below.

Masks

A layer mask hides or reveals parts of a layer without erasing pixels. Paint the mask with black to hide and white to reveal. A selection can be turned into a mask.

Clipping masks

A clipped layer renders only where the layer directly beneath it has pixels. Flat your colours once, then stack shading, highlights and texture on top as clipped layers and paint freely - nothing escapes the silhouette.

• Toggle with Ctrl+Alt+G, or Clip to Layer Below in the layer's right-click menu. Clicking the elbow in a clipped row's left gutter releases it.
• Several layers in a row can clip to the same base; they draw as one bracket pointing at the base, whose name is underlined.
• The base is whichever layer is currently below, so reordering just works. Hiding the base hides everything clipped to it.
• Adjustment layers can be clipped too, which is how you apply a hue shift or a blur to one layer instead of a whole folder.

Alpha lock

Alpha lock confines paint to the pixels a layer already has: colour can change, transparency cannot. It is the single-layer version of a clipping mask - recolour a shape in place without leaving its edges.

• Toggle with /, the padlock at the right of the layers panel header, or Lock Alpha in the right-click menu.
• Applies to the brush, fill, gradient, shape and liquify tools. The eraser is refused, since erasing only removes transparency.
• A locked layer shows a padlock badge on its thumbnail and lights an "Alpha locked" chip under the canvas, because the lock is otherwise invisible.

Adjustment layers

Adjustment layers change the look of everything beneath them, non-destructively:

• Hue / Saturation / Brightness
• Blur
• Stroke

Each has its own painted mask, so the adjustment can be brushed in where you want it. Placed inside a folder, an adjustment clips to that folder.

Filters

Filters (blur, HSV, stroke and more) apply directly to a layer with a live preview, clipped to the current selection.