IdentityCLUTImageGenerator

A lookup table is a cube of color values: the red, green, and blue components of an input color map to the x, y, and z coordinates of a location in that cube, and at that location in the cube is a corresponding output color.

The 2D representation of a 3D color cube is an arrangement of slices.

For example, a 16 x 16 x 16 color cube becomes a horizontal strip of 16 squares, each 16 x 16 pixels (that is, a 256 x 16 image). Each square contains a gradation of red and green components, and together the 16 squares form a gradation for the blue component.

IdentityCLUTImageGenerator.playground generates 2D identity color lookup table images that can be use with image processing frameworks like MetalPetal, GPUImage, SceneKit, etc.

Types

CLUTImageDescriptor

dimension: Dimension of the color lookup table. [0~256]

layout: Layout of the color lookup table image.

CLUTImageLayout

horizontalTileCount: Horizontal blocks of the color lookup table image.

verticalTileCount: Vertical blocks of the color lookup table image.

horizontalTileCount * verticalTileCount should be equal to the CLUTImageDescriptor’s dimension.

Examples

• The identity 16x16x16 horizontal-strip-layout color lookup table image used by SCNCamera.colorGrading can be generated using:

  CLUTImageDescriptor(dimension: 16, layout: CLUTImageLayout(horizontalTileCount: 16, verticalTileCount: 1))
  

• The identity 64x64x64 square-layout color lookup table image used by GPUImage can be generated using:

  CLUTImageDescriptor(dimension: 64, layout: CLUTImageLayout(horizontalTileCount: 8, verticalTileCount: 8))