OpenLIME

Class: LayerCombiner

LayerCombiner

LayerCombiner provides functionality to combine multiple layers using framebuffer operations and custom shaders. It enables complex visual effects by compositing layers in real-time using GPU-accelerated rendering.

Features:

  • Real-time layer composition
  • Custom shader-based effects
  • Framebuffer management
  • Dynamic texture allocation
  • Resolution-independent rendering
  • GPU-accelerated compositing

Use Cases:

  • Layer blending and mixing
  • Image comparison tools
  • Lens effects (see LayerLens)
  • Custom visual effects
  • Multi-layer compositing

Technical Details:

  • Creates framebuffers for each input layer
  • Manages WebGL textures and resources
  • Supports dynamic viewport resizing
  • Handles shader-based composition
  • Maintains proper resource cleanup

new LayerCombiner(options)

Creates a new LayerCombiner instance

Parameters:
Name Type Description
options LayerCombinerOptions

Configuration options
Source:
Throws:

If rasters option is not empty (rasters should be defined in source layers)

Type
Error
Example
```javascript
// Create two base layers
const baseLayer = new OpenLIME.Layer({
  type: 'image',
  url: 'base.jpg'
});

const overlayLayer = new OpenLIME.Layer({
  type: 'image',
  url: 'overlay.jpg'
});

// Create combiner with custom shader
const combiner = new OpenLIME.Layer({
  type: 'combiner',
  layers: [baseLayer, overlayLayer],
  visible: true
});

// Set up blend shader
const shader = new OpenLIME.ShaderCombiner();
shader.mode = 'blend';
combiner.shaders = { 'standard': shader };
combiner.setShader('standard');

// Add to viewer
viewer.addLayer('combined', combiner);
```

Extends

Methods

addControl(name, value)

Adds a shader parameter control

Parameters:
Name Type Description
name string

Control identifier
value *

Initial value
Inherited From:
Overrides:
Source:
Throws:

If control already exists

Type
Error

addShader(id, shader)

Adds a shader to the layer's available shaders

Parameters:
Name Type Description
id string

Unique identifier for the shader
shader Shader

Shader instance to add
Inherited From:
Overrides:
Source:
Throws:

If shader with the same id already exists

Type
Error
Returns:

This layer instance for method chaining

Type
Layer
Example
```javascript
const customShader = new OpenLIME.Shader({...});
layer.addShader('custom', customShader);
layer.setShader('custom');
```

addShaderFilter(filter)

Adds a filter to the current shader

Parameters:
Name Type Description
filter Object

Filter specification
Inherited From:
Overrides:
Source:
Throws:

If no shader is set

Type
Error

clearShaderFilters(name)

Removes all filters from the current shader

Parameters:
Name Type Description
name Object

Filter name
Inherited From:
Overrides:
Source:
Throws:

If no shader is set

Type
Error

derive( [options])

Creates a new Layer that shares tiles with this layer but uses a different shader. This method allows efficient creation of derivative layers that share the same source textures, which is useful for applying different visual effects to the same image data without duplicating resources.

Parameters:
Name Type Argument Default Description
options Object <optional>
 {}

Options for the new layer

Properties
Name Type Argument Description
shaders Object <optional>

Map of shaders for the new layer
defaultShader string <optional>

ID of shader to set as active
label string <optional>

Label for the new layer (defaults to original label)
zindex number <optional>

Z-index for the new layer (defaults to original + 1)
visible boolean <optional>

Layer visibility (defaults to same as original)
transform Transform <optional>

Custom transform (defaults to copy of original)
mipmapBias number <optional>

Custom mipmap bias (defaults to original value)
pixelSize number <optional>

Custom pixel size (defaults to original value)
debug boolean <optional>

Debug mode flag (defaults to original value)
Inherited From:
Overrides:
Source:
Returns:

A new layer sharing textures with this one

Type
Layer
Example
```javascript
// Create a derived layer with edge detection shader
const enhancedShader = new OpenLIME.ShaderEdgeDetection();
const derivedLayer = originalLayer.derive({
    label: 'Edge Detection',
    shaders: { 'edge': enhancedShader },
    defaultShader: 'edge',
    zindex: 10
});
viewer.addLayer('edges', derivedLayer);
```
or
```javascript
const enhancedShader = new OpenLIME.ShaderEdgeDetection();
const derivedLayer = layer.derive({
    label: 'Enhanced Image'
});
derivedLayer.addShader('enhanced', enhancedShader);
derivedLayer.setShader('enhanced');
viewer.addLayer('Enhanced Image', derivedLayer);
```

getControl(name)

Gets the shader parameter control corresponding to name

Parameters:
Name Type Description
name *

The name of the control. return {*} The control
Inherited From:
Overrides:
Source:

getMode()

Gets the current shader visualization mode

Inherited From:
Overrides:
Source:
Returns:

Current mode or null if no shader

Type
string | null

getModes()

Gets available shader modes

Inherited From:
Overrides:
Source:
Returns:

Array of available modes

Type
Array.<string>

getPixelValues(x, y)

Gets pixel values for a specific pixel location Works with both single images and tiled formats

Parameters:
Name Type Description
x number

X coordinate in image space (0,0 at top-left)
y number

Y coordinate in image space (0,0 at top-left)
Inherited From:
Overrides:
Source:
Returns:

Array containing RGBA values for each raster at the specified pixel

Type
Array.<Uint8Array>

getState( [stateMask])

Gets the current layer state

Parameters:
Name Type Argument Default Description
stateMask Object <optional>
 null

Optional mask to filter returned state properties
Inherited From:
Overrides:
Source:
Returns:

Current state object

Type
Object

interpolateControls()

Updates control interpolation

Inherited From:
Overrides:
Source:
Returns:

Whether all interpolations are complete

Type
boolean

<async> loadTile(tile, callback)

Loads and processes a single image tile with optimized resource management. Implements request batching, concurrent loading, and proper error handling.

Parameters:
Name Type Description
tile Object

Tile specification object

Properties
Name Type Argument Description
index string

Unique tile identifier
url string

Base URL for tile resource
start number <optional>

Start byte for partial content (for tarzoom)
end number <optional>

End byte for partial content (for tarzoom)
offsets Array.<Object> <optional>

Byte offsets for interleaved formats
callback function

Completion callback(error, size)
Inherited From:
Overrides:
Source:
Throws:

If tile is already in processing queue

Type
Error
Returns:
Type
Promise.<void>

pixelSizePerMM()

Gets pixel size in millimeters

Inherited From:
Overrides:
Source:
Returns:

Size of one pixel in mm

Type
number

removeShader(id)

Removes a shader from the layer's available shaders

Parameters:
Name Type Description
id string

Identifier of the shader to remove
Inherited From:
Overrides:
Source:
Throws:

If shader with the specified id doesn't exist

Type
Error
Returns:

This layer instance for method chaining

Type
Layer
Example
```javascript
// Remove a shader that's no longer needed
layer.removeShader('oldEffect');
```

removeShaderFilter(name)

Removes a filter from the current shader

Parameters:
Name Type Description
name Object

Filter name
Inherited From:
Overrides:
Source:
Throws:

If no shader is set

Type
Error

setControl(name, value [, dt] [, easing])

Sets a shader control value with optional animation

Parameters:
Name Type Argument Default Description
name string

Control identifier
value *

New value
dt number <optional>

Animation duration in ms
easing string <optional>
 'linear'

Easing function
Inherited From:
Overrides:
Source:
Fires:

setMode(mode)

Sets shader visualization mode

Parameters:
Name Type Description
mode string

Mode to set
Inherited From:
Overrides:
Source:
Fires:

setShader(id)

Sets the active shader

Parameters:
Name Type Description
id string

Shader identifier from registered shaders
Inherited From:
Overrides:
Source:
Fires:
Throws:

If shader ID is not found

Type
Error

setState(state [, dt] [, easing])

Sets the layer state with optional animation

Parameters:
Name Type Argument Default Description
state Object

State object with controls and mode
dt number <optional>

Animation duration in ms
easing string <optional>
 'linear'

Easing function ('linear'|'ease-out'|'ease-in-out')
Inherited From:
Overrides:
Source:

setTransform(tx)

Sets the layer's transform

Parameters:
Name Type Description
tx Transform

New transform
Inherited From:
Overrides:
Source:
Fires:
  • Layer#event:updateSize

setViewport(view)

Sets the layer's viewport

Parameters:
Name Type Description
view Object

Viewport specification

Properties
Name Type Description
x number

X position
y number

Y position
dx number

Width
dy number

Height
Inherited From:
Overrides:
Source:
Fires:

setVisible(visible)

Sets layer visibility

Parameters:
Name Type Description
visible boolean

Whether layer should be visible
Inherited From:
Overrides:
Source:
Fires:

setZindex(zindex)

Sets layer rendering order

Parameters:
Name Type Description
zindex number

Stack order value
Inherited From:
Overrides:
Source:
Fires:

Events

ready

The event is fired when a layer is initialized.

Inherited From:
Overrides:
Source:

update

The event is fired if a redraw is needed.

Inherited From:
Overrides:
Source: