By using second method, obtained image can keep 
density level of original color image. High resolution 
information from panchromatic image are also 
included in obtained image. However, some area of 
obtained result has not high resolution information 
compare with first method. The fused image we would 
like to make is a mixed image of obtained result of first 
method and that of second method. Color adjust 
method was introduced to the first method. The area 
which has low contrast will be change to high by using 
color space transformation. 
Geometric Correction 
SPOT satellite image has large geometric distortion 
because of slant observation. Precise geometric 
correction of both images is necessary for multi sensor 
data fusion. Generally satellite image will be 
geometrically corrected by using GCPs. Both images 
are transformed to map coordinate system by using 
GCPs. Both corrected images are geometrically 
transformed and coincided with each other by using 
control points. 
HSI Transformation and Inverse HSI Transformation 
HSI coordinate system is shown in Fig.2 Color images 
are displayed on the monitor by RGB color system. But, 
HSI color system is better to operate the color 
combination. Where H.S.I mean hue, saturation and 
Intensity of the color. HSI transformation are defined 
as the transformation from RGB color system to HSI 
color system. Inverse HSI transformation also defined 
as the transformation from HSI color system to RGB 
color system. 
Color Adjustment by using Color Space 
Modification 
  
  
  
Point out Fixed Color and Adjustable cur | 
  
  
Determination of Adjust Function over Color Space 
  
  
  
  
Color Adjustment by using Adjust Function 
  
  
Fig.3 The step of color adjustment 
Fixed color was selected from the object image 
Desired color after adjustment was given for each fixed 
color. In fixed color and adjustable color, only on 
representative point is sufficient for adjustment 
Neighboring colors are not considered. Because the 
amount of color adjustment given by the fixed color 
adjustable color pair can be propagate to surrounding 
color by smoothing color space modification. Th 
influenced extent of the amount of color space is 
determined by the system based on following steps 
Determination of adjust function over color spac. 
Adjust function over whole color space is determined 
based on the boundary condition of the correspondence 
of fixed color and adjustable color. Precise steps att 
shown as follows. 
Arbitrary color before color adjustment in Hl 
coordinate system denotes 
S = (1,8.h). 
The color after adjustment for S denotes 
S'z (sh). 
S is the function of S. 
S*z S'(S) (1) 
The amount of adjustment in S denotes 
m-S'-S 
m is also the function of S. 
m = S(S) - S = m(S) (2) 
where, following equation can be written when fixed 
color and adjustable color pair Si,S’i (i=1,2....n). 
mi = S’i-Si = S’(si)-Si = m(Si) (3) 
Various form could be considered for function m. t 
distance function from fixed point Si was used in thi 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996