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Image indexes

Tiago Olivoto

2023-10-22

Source: vignettes/indexes.Rmd
indexes.Rmd

Getting started

In this vignette, you will learn about the color space indexes provided by the package, with a focus on the RGB color space, the HSB color space, and the CIE-Lab color space.

Throughout the vignette, we will delve into the underlying formulas and methodologies used for converting colors between different color spaces, ensuring that you have a comprehensive understanding of how these transformations work.

RGB Color Space

The RGB (Red, Green, Blue) color space is a widely used color representation in computer graphics and digital imaging. In the pliman package, we provide a range of indexes to analyze and manipulate color data within the RGB color space:

Indexes in the RGB Color Space

Abbreviation Name Formula Reference
R Red (650 nm) R
G Green (545 nm) G
B Blue (445 nm) B
NR Normalized Red R / (R + G + B) Yang et al. (2015)
NG Normalized Green G / (R + G + B) Yang et al. (2015)
NB Normalized Blue B / (R + G + B) Yang et al. (2015)
GB Green-Blue Ratio G / B
RB Red-Blue Ratio R / B
GR Green-Red Ratio G / R
BI Brightness Index sqrt((R^2 + G^2 + B^2) / 3) Richardson and Wiegand (1977)
BI2 Brightness Index 2 sqrt((R^2 + G^2 + B^2) / 3)
SCI Soil Colour Index (R - G) / (R + G) Mathieu et al. (1998)
GLI Green Leaf Index ((G-R)+(G-B))/(G+R+G+B) Louhaichi, Borman, and Johnson (2001)
HI Primary Colours Hue Index (2*R-G-B)/(G-B) Escadafal, Belghit, and Ben-Moussa (1994)
NGRDI Normalized Green-Red Difference Index (G-R)/(G+R) Tucker (1979)
NGBDI Normalized Green-Blue Difference Index (G-B)/(G+B) Bannari et al. (1995)
SI Normalized Red-Blue Difference Index (R-B)/(R+B) Escadafal, Belghit, and Ben-Moussa (1994)
I Total intensity R + G + B
S Saturation ((R + G + B) - 3 * B) / (R + G + B)
L Average Intensity (R + G + B) / 3
VARI Visible Atmospherically Resistant Index (G-R)/(G+R-B) Anatoly A. Gitelson et al. (2002a)
HUE Overall Hue Index atan(2*(B-G-R)/30.5*(G-R)) Escadafal, Belghit, and Ben-Moussa (1994)
HUE2 Overall Hue Index 2 atan(2*(R-G-R)/30.5*(G-B)) Escadafal, Belghit, and Ben-Moussa (1994)
BGI Blue Green Pigment B/G Zarco-Tejada et al. (2005)
GRAY 0.299 * R + 0.587 * G + 0.114 * B
GRAY2 ((R^2.2 + (1.5 * G)^2.2 + (0.6 * B)^2.2) / (1 + 1.5^2.2 + 0.6^2.2))^(1/2.2)
GLAI (25 * (G - R) / (G + R - B) + 1.25)
CI Coloration Index ((R - B) / R)
SAT Overall Saturation Index ((max(R, G, B) - min(R, G, B)) / max(R, G, B))
SHP Shape Index (2 * (R - G - B) / (G - B))
RI Redness Index (R^2 / (B * G^3))
SAVI Soild Adjusted Vegetation Index (1 + 0.5)*(G-R)/(G+R+0.5) Li et al. (2010)

Multispectral indexes

{pliman} provides tools to analyze up to 5 bands , which are generally B, G, R, RE (red-edge) and NIR (near-infrared). The following build-in indexes are available.

Abbreviation Name Formula Reference
NDVI Normalized Diference Vegetation Index (NIR - R) / (NIR + R) Kriegler (1969)
PSRI Plant Senescence Reflectance Index (R-G)/RE Merzlyak et al. (1999)
GNDVI Normalized Difference NIR/G (NIR - G) / (NIR + G) Anatoly A. Gitelson and Merzlyak (1996)
RVI Ratio Vegetation Index R/NIR Pearson and Miller (1972)
VIN Vegetation Index Number NIR/R Pearson and Miller (1972)
NDRE Normalized Difference NIR/Rededge (NIR-RE)/(NIR+RE) A. Gitelson and Merzlyak (1994)
SAVI Soild Adjusted Vegetation Index ((NIR-R) / (NIR + R + 0.5) * 1 + 0.5) A. R. Huete (1988)
TSAVI Transformed Soil Adjusted Vegetation Index (2*((NIR-2)*(R-1)))/(R+2*(NIR-1)+0.5*(1+2*2)) Baret, Guyot, and Major (1989)
TVI Transformed Vegetation Index sqrt((NIR - R) / (NIR + R) + 0.5) Broge and Leblanc (2001)
CVI Chlorophyll vegetation index NIR*(R/G^2) Vincini, Frazzi, and D’Alessio (2008)
EVI Enhanced Vegetation Index 2.5*(NIR-R)/(NIR+6*R-7.5*B+1) A. Huete et al. (2002)
CIG Chlorophyll Index Green (NIR/G)-1 Anatoly A. Gitelson, Gritz †, and Merzlyak (2003)
CIRE Chlorophyll Index - Red-Edge (NIR/RE)-1 Anatoly A. Gitelson, Gritz †, and Merzlyak (2003)
RESR Red-Edge Simple Ratio  NIR/RE Anatoly A. Gitelson et al. (2002b)
GDVI Green Difference Vegetation Index NIR-G Index DataBase (2023)
REDVI Red-Edge Difference Vegetation Index NIR-RE Jordan (1969)
NDWI Normalized Difference Water Index (G-NIR)/(G+NIR) McFEETERS (1996)
CVI Chlorophyll vegetation index NIR * (R/(G*G)) Index DataBase (2023)
PNDVI Pan NDVI ((NIR-(G+R+B))/(NIR+(G+R+B))) Index DataBase (2023)
CCCI Canopy Chlorophyll Content Index ((NIR-R)/(NIR+R))/((NIR-R)/(NIR+R)) Index DataBase (2023)
OSAVI Optimized Soil Adjusted Vegetation Index (NIR-R)/(NIR+R+0.16) Rondeaux, Steven, and Baret (1996)
GOSAVI Green Optimized Soil Adjusted Vegetation Index (NIR-G)/(NIR+G+0.16) Index DataBase (2023)
GSAVI Green Soil Adjusted Vegetation Index ((NIR-G)/(NIR+G+0.5))*(1+0.5) Index DataBase (2023)
BAI Burn Area Index 1/((0.1 - R)^2 + (0.06 - NIR)^2) Chuvieco, Martín, and Palacios (2002)
GEMI Global Environmental Monitoring Index (2*(NIR*NIR-R*R)+1.5*NIR+0.5*R)/(NIR+R+0.5)*(1-0.25*(2*(NIR*NIR-R*R)+1.5*NIR+0.5*R)/(NIR+R+0.5))-((R-0.125)/(1-R)) Pinty and Verstraete (1992)
MSAVI Modified Soil Adjusted Vegetation Index  (1/2)*(2*(NIR+1)-sqrt((2*NIR+1)*2-8*(NIR-R))) Qi et al. (1994)
MSAVI2 Modified Soil Adjusted Vegetation Index 2 (2 * NIR + 1 - sqrt((2 * NIR + 1)^2 - 8 * (NIR - R) )) / 2 Qi et al. (1994)
VIG Vegetation Index (green) (G-R)/(G+R) Anatoly A. Gitelson et al. (2002c)
VIRE Vegetation Index (red-edge) (RE-R)/(RE+R) Anatoly A. Gitelson et al. (2002c)
VARIRE Visible Atmospherically Resistant Index (red-edge) (RE - 1.7 * R + 0.7 * B) / (RE + 2.3 * R - 1.3 * B) Anatoly A. Gitelson et al. (2002c)
ARVI Atmospherically resistant vegetation index (NIR - (R - 0.1*(R-B))) / (NIR + (R - 0.1*(R-B))) Kaufman and Tanre (1992)
GARI Green Atmospherically Resistant Index (NIR - (1.7 * (B-R))) / (NIR + (1.7 * (B-R))) Anatoly A. Gitelson, Kaufman, and Merzlyak (1996)
GRVI Green Ratio Vegetation Index NIR / G Sripada et al. (2006)
IPVI Infrared Percentage Vegetation Index NIR / (NIR + R) Crippen (1990)
LAI Leaf Area Index 3.368 * (2.5*(NIR-R)/(NIR+6*R-7.5*B+1)) - 0.118 Boegh et al. (2002)
MSR Modified Simple Ratio (NIR / R - 1) / (sqrt(NIR / R) + 1) Chen (1996)
NLI Non-Linear index (NIR ^2 - R) / (NIR ^2 + R) Goel and Qin (1994)
RDVI Renormalized Difference Vegetation Index (NIR - R) / (sqrt(NIR + R)) Roujean and Breon (1995)
TDVI Transformed Difference Vegetation Index 1.5 * ((NIR - R) / (sqrt(NIR ^2 + R + 0.5))) Bannari, Asalhi, and Teillet (2002)
WDRVI Wide Dynamic Range Vegetation Index (0.2 * NIR - R) / (0.2 * NIR + R) Anatoly A. Gitelson (2004)
ARI Anthocyanin Reflectance Index (1 / G) - (1 / RE) A. A. Gitelson, Merzlyak, and Chivkunova (2001)

Usefull references

HSB Color Space

The HSB (Hue, Saturation, Brightness) color space is an alternative color representation that emphasizes the perceptual aspects of color.

Conversion to CIE-Lab

The rgb_to_hsb() function can be used to convert RGB to HSB color space. The conversion is performed according to described by Karcher and Richardson (2003).

  • Hue (H):
    • If max (R,G,B) = R, H = 60 * (G - B) / (max(R,G,B) - min(R,G,B))
    • If max (R,G,B) = G, H = 60 * (2 + (B - R) / (max(R,G,B) - min(R,G,B))
    • If max (R,G,B) = B, H = 60 * (4 + (R - G) / (max(R,G,B) - min(R,G,B))
  • Saturation (S):
    • S = (max(R,G,B) - min(R,G,B)) / max(R,G,B)
  • Brightness (B):
    • B = max(R,G,B)

Indexes in the HSB Color Space

Abbreviation Name Formula Reference
DGCI Dark Green Color Inde ((H - 60) / 60 + (1 - S/100) + (1 - B/100)) / 3 Karcher and Richardson (2003)

CIE-Lab Color Space

The CIE-Lab (CIELAB) color space is a color model that approximates human vision and is often used for color difference analysis and color correction. In the pliman package, we support the conversion from RGB to Lab color space.

Conversion to CIE-Lab

The conversion from RGB to Lab is performed by the rgb_to_lab() function in the pliman package. This involves several steps, including the transformation from RGB to sRGB, sRGB to XYZ, and then from XYZ to Lab.

To understand the specific formulas and steps involved in this conversion, please refer to the detailed formulas.

Indexes in the CIE-Lab Color Space (soon)

Abbreviation Name Formula Reference

References

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