Gamma LAT: Reference Manual

ras_to_hsi

NAME
ras_to_hsi - Combine 3 raster (SUN or BMP) raster images into hue/saturation/intensity (HSI) 24-bit composite raster image.

SYNOPSIS
ras_to_hsi <HUE> <SATURATION> <INTENSITY> <ras_out> [LR] [color_table_flag]

<HUE>	input (8-bit) SUN or BMP format raster image to be used for the HUE channel
<SATURATION>	input (8-bit) SUN or BMP format raster image to be used for the SATURATION channel
<INTENSITY>	input (8-bit) SUN or BMP format raster image to be used forthe INTENSITY channel
<ras_out>	output 24-bit SUN or BMP format raster image
[LR]	image mirror flag: 1: normal (default) -1: mirror image
[color_table_flag]	color table flag 0: use (red+green+blue)/3 as value (default) 1: scale input values linearly to 255

EXAMPLE
ras_to_hsi 19990421_19990422.unw.ras 19990421_19990422.cc.ras 19990421_19990422.pwr1.ras 19990421_19990422.unw_hsi.ras 1 0

Combines the 3 input 8-bit SUN raster images into an HSI 24-bit Sun format raster image. It is assumed that the 3 input images are all 8-bit greyscale coded images.

ras_to_hsi 19990421_19990422.soil_moisture.bmp unity.bmp 19990421.mli.bmp 19990421_19990422.soil_moisture.bmp 1 1

Combines the soil moisture map (which may contain for example just 5 levels of soil moisture) with the backscatter image. The soil moisture information is color coded (i.e. used as hue channel), the backscatter intensity is used as image brightness (i.e. intensity channel). As saturation channel a file containing just 1.0 values was used.

DESCRIPTION
ras_to_hsi supports the visualization of data by combination of 3 8-bit images in SUN raster or BMP format into a single hue/saturation/intensity (HSI) image.This visualization tool was mainly designed for images containing a grey scale coding of one parameter. Images with both the coherence (as color) and intensity (as brightness), or phase (as color) and the intensity (as brightness) are not useful as inputs.The data numbers (DN) values in the images are mapped through the color table to RGB triplets. As an example, a black and white image contains only the values 0 and 1. The color table values associated are (0,0,0) and (255,255,255). With a selection of the color_table_flag = 0 the two values are interpreted as 0 and 255, resulting in almost the same color in the HSI image. With a selection of the color_table_flag = 1 the two values are interpreted as 0 and 1. The entity of occurring values, in this case 2, is then homogeneously spread over the entire color wheel values (0,255) resulting in the values 0 and 128 resulting in complementary colors in the HSI image. Images appropriate as input for ras_to_hsi may be generated using the programs such as ras_linear and ras_dB.

The display of multiple channels is very important for the interpretation of the results. A phase image or a soil moisture map, for example, show little land features making the orientation in such an image very difficult. In combination with a backscatter or coherence image this problem is solved and the phase or soil moisture information may be associated to surface features.

SEE ALSO
ras_to_rgb, display.h, rasterfile.h, bmp_image.h