Colorizer

A colorizer specifies a mapping between values and pixels/objects of an output image. Different variants of colorizers perform different kinds of mapping.

Usually, there are two miscellaneous fields in each colorizer, namely noDataColor and defaultColor. The field noDataColor is used for all missing, NaN or no data values. The defaultColor is used for all overflowing values, for instance, if there are breakpoints defined from 0 to 10, but a value of -5 or 11 is mapped to a color.

Colors are defined as RGBA arrays, where the first three values refer to red, green and blue and the fourth one to alpha, which means transparency. The values range from 0 to 255. For instance, [255, 255, 255, 255] is opaque white and [0, 0, 0, 127] is semi-transparent black.

Linear Gradient

A linear gradient linearly interpolates values within breakpoints of a color table.

Example JSON

{
  "type": "linearGradient",
  "breakpoints": [
    {
      "value": 1.0,
      "color": [255, 255, 255, 255]
    },
    {
      "value": 2.0,
      "color": [0, 0, 0, 255]
    }
  ],
  "noDataColor": [0, 0, 0, 0],
  "defaultColor": [0, 0, 0, 0]
}

Logarithmic Gradient

A logarithmic gradient logarithmically interpolates values within breakpoints of a color table and allows only positive values.

Errors

Services report errors that try to use a logarithmic gradient specification with values where value <= 0.

Example JSON

{
  "type": "logarithmicGradient",
  "breakpoints": [
    {
      "value": 1.0,
      "color": [255, 255, 255, 255]
    },
    {
      "value": 2.0,
      "color": [0, 0, 0, 255]
    }
  ],
  "noDataColor": [0, 0, 0, 0],
  "defaultColor": [0, 0, 0, 0]
}

Palette

A palette maps values as classes to a certain color. Unmapped values result in the NO DATA color.

Example JSON

{
  "type": "palette",
  "colors": {
    "1": [255, 255, 255, 255],
    "2": [0, 0, 0, 255]
  },
  "noDataColor": [0, 0, 0, 0],
  "defaultColor": [0, 0, 0, 0]
}