ColorMapping - Color Mapping¶

Maps an input label image to 8-bits RGB using look-up tables.

Detailed description¶

This application allows one to map a label image to a 8-bits RGB image (in both ways) using different methods.

-The custom method allows one to use a custom look-up table. The look-up table is loaded from a text file where each line describes an entry. The typical use of this method is to colorise a classification map. -The continuous method allows mapping a range of values in a scalar input image to a colored image using continuous look-up table, in order to enhance image interpretation. Several look-up tables can been chosen with different color ranges.

-The optimal method computes an optimal look-up table. When processing a segmentation label image (label to color), the color difference between adjacent segmented regions is maximized. When processing an unknown color image (color to label), all the present colors are mapped to a continuous label list.

The support image method uses a color support image to associate an average color to each region.

Parameters¶

This section describes in details the parameters available for this application. Table [1] presents a summary of these parameters and the parameters keys to be used in command-line and programming languages. Application key is ColorMapping .

[1]	Table: Parameters table for Color Mapping.

Parameter Key	Parameter Name	Parameter Type
in	Input Image	Input image
out	Output Image	Output image
op	Operation	Choices
op labeltocolor	Label to color	Choice
op colortolabel	Color to label	Choice
op.colortolabel.notfound	Not Found Label	Int
method	Color mapping method	Choices
method custom	Color mapping with custom labeled look-up table	Choice
method continuous	Color mapping with continuous look-up table	Choice
method optimal	Compute an optimized look-up table	Choice
method image	Color mapping with look-up table calculated on support image	Choice
method.custom.lut	Look-up table file	Input File name
method.continuous.lut	Look-up tables	Choices
method.continuous.lut red	Red	Choice
method.continuous.lut green	Green	Choice
method.continuous.lut blue	Blue	Choice
method.continuous.lut grey	Grey	Choice
method.continuous.lut hot	Hot	Choice
method.continuous.lut cool	Cool	Choice
method.continuous.lut spring	Spring	Choice
method.continuous.lut summer	Summer	Choice
method.continuous.lut autumn	Autumn	Choice
method.continuous.lut winter	Winter	Choice
method.continuous.lut copper	Copper	Choice
method.continuous.lut jet	Jet	Choice
method.continuous.lut hsv	HSV	Choice
method.continuous.lut overunder	OverUnder	Choice
method.continuous.lut relief	Relief	Choice
method.continuous.min	Mapping range lower value	Float
method.continuous.max	Mapping range higher value	Float
method.optimal.background	Background label	Int
method.image.in	Support Image	Input image
method.image.nodatavalue	NoData value	Float
method.image.low	lower quantile	Int
method.image.up	upper quantile	Int
ram	Available RAM (Mb)	Int
inxml	Load otb application from xml file	XML input parameters file
outxml	Save otb application to xml file	XML output parameters file

Input Image: Input image filename.

Output Image: Output image filename.

Operation: Selection of the operation to execute (default is : label to color). Available choices are:

Label to color
Color to label

Not Found Label: Label to use for unknown colors.

Color mapping method: Selection of color mapping methods and their parameters. Available choices are:

Color mapping with custom labeled look-up table: Apply a user-defined look-up table to a labeled image. Look-up table is loaded from a text file.

Look-up table file: An ASCII file containing the look-up table with one color per line (for instance the line ‘1 255 0 0’ means that all pixels with label 1 will be replaced by RGB color 255 0 0) Lines beginning with a # are ignored.

Color mapping with continuous look-up table: Apply a continuous look-up table to a range of input values.

Look-up tables: Available look-up tables. Available choices are:

Red

Green

Blue

Grey

Hot

Cool

Spring

Summer

Autumn

Winter

Copper

Jet

HSV

OverUnder

Relief

Mapping range lower value: Set the lower input value of the mapping range.

Mapping range higher value: Set the higher input value of the mapping range.

Compute an optimized look-up table: [label to color] Compute an optimal look-up table such that neighboring labels in a segmentation are mapped to highly contrasted colors. [color to label] Searching all the colors present in the image to compute a continuous label list.

Background label: Value of the background label.

Color mapping with look-up table calculated on support image

Support Image: Support image filename. For each label, the LUT is calculated from the mean pixel value in the support image, over the corresponding labeled areas. First of all, the support image is normalized with extrema rejection.

NoData value: NoData value for each channel of the support image, which will not be handled in the LUT estimation. If NOT checked, ALL the pixel values of the support image will be handled in the LUT estimation.

lower quantile: lower quantile for image normalization.

upper quantile: upper quantile for image normalization.

Available RAM (Mb): Available memory for processing (in MB).

Load otb application from xml file: Load otb application from xml file.

Save otb application to xml file: Save otb application to xml file.

Example¶

To run this example in command-line, use the following:

otbcli_ColorMapping -in ROI_QB_MUL_1_SVN_CLASS_MULTI.png -method custom -method.custom.lut ROI_QB_MUL_1_SVN_CLASS_MULTI_PNG_ColorTable.txt -out Colorized_ROI_QB_MUL_1_SVN_CLASS_MULTI.tif

To run this example from Python, use the following code snippet:

#!/usr/bin/python

# Import the otb applications package
import otbApplication

# The following line creates an instance of the ColorMapping application
ColorMapping = otbApplication.Registry.CreateApplication("ColorMapping")

# The following lines set all the application parameters:
ColorMapping.SetParameterString("in", "ROI_QB_MUL_1_SVN_CLASS_MULTI.png")

ColorMapping.SetParameterString("method","custom")

ColorMapping.SetParameterString("method.custom.lut", "ROI_QB_MUL_1_SVN_CLASS_MULTI_PNG_ColorTable.txt")

ColorMapping.SetParameterString("out", "Colorized_ROI_QB_MUL_1_SVN_CLASS_MULTI.tif")

# The following line execute the application
ColorMapping.ExecuteAndWriteOutput()

Limitations¶

The segmentation optimal method does not support streaming, and thus large images. The operation color to label is not implemented for the methods continuous LUT and support image LUT.: ColorMapping using support image is not threaded.

Authors¶

This application has been written by OTB-Team.