# GSLayer Background

*API Collection*

Background content and reference images associated with a layer.

## Overview

A layer background is a secondary layer used for editable outlines and related content.

A background image is independent of the background layer. It is attached directly to the layer and can be positioned and transformed as a reference image.

## Topics

### Background Layer

- [`GSBackgroundLayer`](/Core/GlyphsCore/GSBackgroundLayer) — Editable background content associated with a foreground layer.
- [`GSLayer.background`](/Core/GlyphsCore/GSLayer/background) — Editable background content associated with the layer.
- [`GSLayer hasBackground`](/Core/GlyphsCore/GSLayer/hasBackground) — Whether a background layer has been created.
- [`GSLayer contentToBackgroundCheckSelection:keepOldBackground:`](/Core/GlyphsCore/GSLayer/contentToBackgroundCheckSelection:keepOldBackground:) — Copies shapes and anchors to the corresponding foreground or background layer.
- [`GSLayer swapForegroundWithBackground`](/Core/GlyphsCore/GSLayer/swapForegroundWithBackground) — Exchanges shapes, anchors, and hints between the foreground and background layers.

### Background Image

- [`GSBackgroundImage`](/Core/GlyphsCore/GSBackgroundImage) — A reference image attached directly to a layer.
- [`GSLayer.backgroundImage`](/Core/GlyphsCore/GSLayer/backgroundImage) — A reference image attached directly to the layer.
- [`GSLayer.hasBackgroundImage`](/Core/GlyphsCore/GSLayer/hasBackgroundImage) — Whether a background image is attached directly to the layer.
- [`GSLayer addBackgroundImageWithURL:`](/Core/GlyphsCore/GSLayer/addBackgroundImageWithURL:) — Adds an image from a file URL.

## See Also

- [GSLayer Kind](/Core/GlyphsCore/GSLayer-Kind) — The different roles that a layer can serve.
- [GSLayer Shapes](/Core/GlyphsCore/GSLayer-Shapes) — The paths and components that form the outline of a layer.
- [GSLayer Bounds](/Core/GlyphsCore/GSLayer-Bounds) — Bounding rectangles of outlines, selections, and metrics.
- [GSLayer Metrics](/Core/GlyphsCore/GSLayer-Metrics) — Side bearings, baseline offsets, layer box, and metrics keys.
- [GSLayer Grid](/Core/GlyphsCore/GSLayer-Grid) — Setting for rounding coordinates on a layer.
- [GSLayer Anchors](/Core/GlyphsCore/GSLayer-Anchors) — Named attachment points on a layer.
- [GSLayer Hints](/Core/GlyphsCore/GSLayer-Hints) — Manual and generated hint data on a layer.
- [GSLayer Guides](/Core/GlyphsCore/GSLayer-Guides) — Layer-local guides used while editing outlines.
- [GSLayer Kerning](/Core/GlyphsCore/GSLayer-Kerning) — Spacing adjustment between specific layers.
- [GSLayer Annotations](/Core/GlyphsCore/GSLayer-Annotations) — Layer-local notes displayed with a glyph.
- [GSLayer Interpolation](/Core/GlyphsCore/GSLayer-Interpolation) — Axis coordinates and rules that place layers in a design space.
- [GSLayer Color](/Core/GlyphsCore/GSLayer-Color) — Colors used to draw a layer.
- [GSLayer Attributes](/Core/GlyphsCore/GSLayer-Attributes) — Additional values stored for a layer.
- [GSLayer Inspection](/Core/GlyphsCore/GSLayer-Inspection) — Intersections between layer outlines and line segments.
- [GSLayer Editing](/Core/GlyphsCore/GSLayer-Editing) — Operations for modifying outlines and other layer content.