Utility Functions

Visualizers

Visualizers are JavaScript classes with a method process which evaluates the representation value for a pixel from pixel’s band values.

ColorMapVisualizer

Sets the color from a discrete color map.

Parameters

valColPairs Array<[number, number]>

Examples

const map = [
  [200, 0xff0000],
  [300, 0x0000ff ],
];

const visualizer = new ColorMapVisualizer(map);
visualizer.process(199); // returns [ 1, 0, 0 ]
visualizer.process(200); // returns [ 1, 0, 0 ]
visualizer.process(250); // returns [ 1, 0, 0 ]
visualizer.process(299); // returns [ 1, 0, 0 ]
visualizer.process(300); // returns [ 0, 0, 1 ]

process

Returns interpolated color for value.

Parameters

val number

Returns [number, number, number] normalized RGB triplet.

createDefaultColorMap

Creates ColorMapVisualizer with following valColPairs

[
  [-1.0, 0x000000],
  [-0.2, 0xff0000],
  [-0.1, 0x9a0000],
  [0.0, 0x660000],
  [0.1, 0xffff33],
  [0.2, 0xcccc33],
  [0.3, 0x666600],
  [0.4, 0x33ffff],
  [0.5, 0x33cccc],
  [0.6, 0x006666],
  [0.7, 0x33ff33],
  [0.8, 0x33cc33],
  [0.9, 0x006600]
]

ColorRampVisualizer

Interpolates a color based on the given color ramps.

Parameters

ramps Array<[number, number]> Array of color ramps, which are defined as a pair of numbers - the ramp start and the ramp starting color.

Examples

const ramps = [
  [200, 0xff0000],
  [300, 0x0000ff ],
];

const visualizer = new ColorRampVisualizer(ramps);
visualizer.process(199); // [ 1, 0, 0 ]
visualizer.process(200); // [ 1, 0, 0 ]
visualizer.process(250); // [ 0.5019607843137255, 0, 0.5019607843137255 ]
visualizer.process(299); // [ 0.011764705882352941, 0, 0.9882352941176471 ]
visualizer.process(300); // [ 0, 1, 0 ]

process

Returns interpolated color for value.

Parameters

value number

Returns [number, number, number] normalized RGB triplet.

This is a piecewise linear function which compresses highlights. The minValue and maxValue will be mapped inside the interval [ 0, 1 ]. However, if maxValue lies in (0, 1) a second function which increases much more slowly will be used to further map the values which are mapped to 0.92 and above (see the figure below). This increases the visualized dynamic range while keeping most of the interval of interest linear. Useful, for example, for true color, with a maxValue of 0.4 to still keep some detail in clouds.

Parameters

minValue number the value which will be mapped to 0. All values smaller than minValue will also be mapped to 0. (optional, default 0.0)
maxValue number the value which controls the position of the boundary point between both linear functions. It will be mapped to approx. 0.9259, while values greater than or equal to (2*maxValue - minValue) will be mapped to 1 (see the figure above). (optional, default 1.0)
gain (optional, default 1.0)
offset (optional, default 0.0)
gamma (optional, default 1.0)

Examples

const visualizer = new HighlightCompressVisualizer(0.1, 0.4)

visualizer.process(0); // will return 0
visualizer.process(0.1); // will return 0
visualizer.process(0.25); // will return 0.5
visualizer.process(0.376); // will return 0.92. Note: 0.376 = minValue + 0.92*(maxValue - minValue)
visualizer.process(0.4); // will return 0.9259
visualizer.process(0.7); // will return 1 Note: 0.7 is the smallest value mapped to 1.
visualizer.process(1.1); // will return 1

process

Returns mapped value.

Parameters

val number the input value to be mapped.
i number the index of val. This is EO Browser specific.

Returns [number] mapped value.

Helper functions

Helper functions that can be used in custom scripts.

int2rgb

Transforms a color as integer into RGB triplet.

Parameters

color number as integer

Examples

int2rgb(255);    // returns [ 0, 0, 255 ]
int2rgb(256);    // returns [ 0, 1, 0 ]
int2rgb(65537);  // returns [ 1, 0, 1 ]

Returns [number, number, number]

rgb2int

Inverse of the int2rgb function. Transforms a RGB triplet into integer.

Parameters

color [number, number, number] as RGB triplet

Examples

rgb2int([0, 0, 255]);  // returns 255
rgb2int([0, 1, 0]);    // returns 256
rgb2int([1, 0, 1]);    // returns 65537

Returns number

combine

Combines two colors.

Parameters

color1 number The first color defined as an array of values.
color2 number The second color defined as an array of values.
alpha number A share of the first color defined as a floating point between 0 and 1.

Examples

combine([100, 0, 0], [0, 100, 0], 1);   // returns [ 100, 0, 0 ]
combine([100, 0, 0], [0, 100, 0], 0);   // returns [ 0, 100, 0 ]
combine([100, 0, 0], [0, 100, 0], 0.5); // returns [ 50, 50, 0 ]

Returns number The combined color defined as an array of values.

index

Calculate difference divided by sum

Parameters

x number first value
y number second value

Examples

index(0.6, 0.4); // returns 0.2
index(0.5, -0.5); //returns 0.0

Returns number (x - y) / (x + y), if sum is 0 returns 0

inverse

Calculate inverse value

Parameters

x number value

Examples

inverse(2.0); // returns 0.5
inverse(5.0); // returns 0.2
inverse(0); // returns 1.7976931348623157E308

Returns number inverse of value of x (1 / x), if x is 0 returns JAVA_DOUBLE_MAX_VAL

valueMap

Maps a value to another value bound by an interval (from,to].

intervals = [-10, -5, 0, 5, 10], values = [-100,-50, 0, 50, 100]
defines the following mapping:
(-inf, -10]  => -100
(-10, -5] => -50
(-5,0] => 0
(0, 5] => 50
(5, +inf) => 100

Parameters

value number input value
intervals [number] array of numbers in ascending order defining intervals
values [number] output value for the given interval

Examples

valueMap(5, [1, 3, 5, 7, 10], [100, 300, 500, 700, 900]); // returns 500
valueMap(1, [1, 3, 5, 7, 10], [100, 300, 500, 700, 900]); // returns 100
valueMap(2, [1, 3, 5, 7, 10], [100, 300, 500, 700, 900]); // returns 300
valueMap(12, [1, 3, 5, 7, 10], [100, 300, 500, 700, 900]); // returns 900
valueMap(50); // returns 50

Returns number

valueInterpolate

Interpolates a value to another value bound by an interval (from,to]. Values at far ends of defined intervals are clamped to min/max value. This function is a replacement for the deprecated colorBlend function.

intervals = [-10, -5, 0, 5, 10], values = [-1000,-50, 0, 50, 1000]
defines the following mapping:
(-inf, -10]  => -1000
(-10, -5] => (-1000, -50]
(-5,0] => (-50,0]
(0, 5] => (0,50]
(5, 10] => (50,1000]
(10, +inf) => 1000

Parameters

value number input value
intervals Array<number> array of numbers in ascending order defining intervals
values (Array<number> | Array<Array<number>>) output interval for the given value/interval of the intervals array

Examples

valueInterpolate(0, [-10, -5, 0, 5, 10], [-1000,-50, 0, 50, 1000]); // returns 0
valueInterpolate(-10, [-10, -5, 0, 5, 10], [-1000,-50, 0, 50, 1000]); // returns -1000
valueInterpolate(9, [-10, -5, 0, 5, 10], [-1000,-50, 0, 50, 1000]); // returns 810
valueInterpolate(50); // returns 50
valueInterpolate(0.1, [0, 0.2, 0.4, 0.6, 0.8, 1], [
  [0, 0, 0],
  [0.1, 0.2, 0.5],
  [0.25, 0.4, 0.5],
  [0.4, 0.6, 0.5],
  [0.75, 0.8, 0.5],
  [1, 1, 0.5]
]); // return [0.05, 0.1, 0.25]

Returns (number | Array<number>)

Constants

JAVA_DOUBLE_MAX_VAL

 const JAVA_DOUBLE_MAX_VAL = 1.7976931348623157E308;

Type: number

blueRed

const blueRed = [
  [1.000, 0x000080],
  [0.875, 0x0000FF],
  [0.625, 0x00FFFF],
  [0.375, 0xFFFF00],
  [0.125, 0xFF0000],
  [0.000, 0x800000]
]

Type: Array<[number, number]>

redTemperature

const redTemperature = [
  [1.000, 0x000000],
  [0.525, 0xAE0000],
  [0.300, 0xFF6E00],
  [0.250, 0xFF8600],
  [0.000, 0xFFFFFF]
]

Type: Array<[number, number]>

greenWhite

const greenWhite = [
  [1.000, 0x000000],
  [0.600, 0x006600],
  [0.300, 0x80B300],
  [0.000, 0xFFFFFF]
]

Type: Array<[number, number]>

colorBlend

Parameters

value number input value
limits Array<number> array of numbers in ascending order defining intervals
colors (Array<number> | Array<Array<number>>) output interval for the given value/interval of the intervals array

Returns (number | Array<number>)

Meta

deprecated: See valueInterpolate

Landsat8C2QaBandConditions

Cloud confidence, cloud shadow confidence, snow ice confidence and cirrus confidence represent levels of confidence that a condition exists:

0 = “Not Determined”
1 = “Low” = Low confidence.
2 = “Medium / Reserved” = Medium only for cloud confidence.
3 = “High” = High confidence.

Type: Object

Properties

fill number 0 for image data, 1 for fill data
dilatedCloud number 0 for cloud is not dilated or no cloud, 1 for cloud dilation
cirrus number 0 for no confidence level or low confidence, 1 for high confidence cirrus
cloud number 0 for cloud confidence is not high, 1 for high confidence cloud
cloudShadow number 0 for cloud shadow confidence is not high, 1 for high confidence cloud shadow
snow number 0 for snow/ice confidence is not high, 1 for high confidence snow cover
clear number 0 if cloud or dilated cloud, or else 1
water number 0 for land or cloud, 1 for water
cloudConfidence number
cloudShadowConfidence number
snowIceConfidence number
cirrusConfidence number

decodeL8C2Qa

Decodes Landsat 8 Collection 2 Quality Assessment band conditions.

Parameters

value integer band pixel (16-bit value)

Examples

decodeL8C2Qa(55052);
// returns {
//   cirrus: 1, cirrusConfidence: 3,
//   clear: 0,
//   cloud: 1,
//   cloudConfidence: 3,
//   cloudShadow: 0,
//   cloudShadowConfidence: 1,
//   dilatedCloud: 0,
//   fill: 0,
//   snow: 0,
//   snowIceConfidence: 1,
//   water: 0
// }

Returns Landsat8C2QaBandConditions

decodeS3OLCIQualityFlags

Unpacks bit-packed Sentinel 3 OLCI Quality Flags values.

Parameters

value integer QUALITY_FLAGS band DN value (32-bit value)

Returns object An object containing the following keys with either 0 or 1 values: land, coastline, fresh_inland_water, tidal_region, bright, straylight_risk, invalid, cosmetic, duplicated, sun_glint_risk, dubious, saturatedBxy (where xy is the band number, e.g. saturatedB01).