blend.sh(1)	       Grass User's Manual	      blend.sh(1)



NNAAMMEE
       bblleenndd..sshh  - Combines the red, green, and blue color compo-
       nents of two raster map layers.
       _(_G_R_A_S_S _S_h_e_l_l _S_c_r_i_p_t_)

SSYYNNOOPPSSIISS
       bblleenndd..sshh file1 file2 perc outbase

DDEESSCCRRIIPPTTIIOONN
       _b_l_e_n_d_._s_h is a Bourne shell (sh(1))  script  that  extracts
       the red (R), green (G), and blue (B) color components from
       each of two raster  map	layers,  and  creates  three  new
       raster  map layers whose category values respectively rep-
       resent the combined red, combined blue, and combined green
       color  values  from the two input layers.  Category values
       in each of the output map  layers  will	fall  within  the
       range of 0 - 255.


       The  R,G,B values from the two input map layers (_f_i_l_e_1 and
       _f_i_l_e_2) are not simply added together, but are instead com-
       bined  by a user-named percentage (_p_e_r_c) of the R,G,B val-
       ues  in	_f_i_l_e_1.	 Specifically,	_b_l_e_n_d_._s_h  executes  three
       _r_._m_a_p_c_a_l_c statements that:

	       convert the R,G,B values in _f_i_l_e_1 and _f_i_l_e_2 to the
	      range 0 - 255;

	      multiply the R, G, and B values in _f_i_l_e_1 by a user-
	      named percentage (_p_e_r_c);

	       multiply the R, G, and B values in _f_i_l_e_2 by (100 -
	      _p_e_r_c)%;

	       create three new raster map layers, whose category
	      values  represent the summed R, summed G, or summed
	      B values resulting from (2) and (3).  Resulting  R,
	      G,  and  B  values  will	respectively be stored in
	      three new raster map layers named  _o_u_t_b_a_s_e.r,  _o_u_t_-
	      _b_a_s_e.g and _o_u_t_b_a_s_e.b.


OOPPTTIIOONNSS
       This  program runs non-interactively;  the user must state
       all parameter values on the command line.

   PPaarraammeetteerrss::
       _f_i_l_e_1  Name of a first raster map layer, whose R, G, and B
	      color components will be combined with those of the
	      second raster map layer (_f_i_l_e_2) named.  The percent
	      value (_p_e_r_c) given will apply to _f_i_l_e_1.

       _f_i_l_e_2  Name of a second raster map layer, whose color com-
	      ponents will be combined with those of _f_i_l_e_1.   The
	      percent  value (_p_e_r_c) given will apply to the R,G,B
	      values in _f_i_l_e_1.	The R, G, and B values	in  _f_i_l_e_2
	      will be multiplied by (100 - _p_e_r_c)%.

       _p_e_r_c   Percentage  or  amount of the color contribution in
	      terms of color intensity.  This value is multiplied
	      by the R,G,B values in _f_i_l_e_1.

       _o_u_t_b_a_s_e
	      The  root name assigned to each of the three output
	      files created.  A suffix	is  added  to  each  file
	      name,  indicating  which	hold  the red, green, and
	      blue color values.


NNOOTTEESS
       _b_l_e_n_d_._s_h executes three	_r_._m_a_p_c_a_l_c  statements:	rr..mmaappccaallcc
       "_o_u_t_b_a_s_e.r  =  r#_f_i_l_e_1  * ._p_e_r_c + (1.0 - ._p_e_r_c) * r#_f_i_l_e_2"
       rr..mmaappccaallcc "_o_u_t_b_a_s_e.g = g#_f_i_l_e_1 * ._p_e_r_c + (1.0 -	._p_e_r_c)	*
       g#_f_i_l_e_2"  rr..mmaappccaallcc  "_o_u_t_b_a_s_e.b = b#_f_i_l_e_1 * ._p_e_r_c + (1.0 -
       ._p_e_r_c) * b#_f_i_l_e_2"



       It uses the # operator  to  separately  extract	the  red,
       green, and blue components in the named raster map layers,
       essentially allowing color separates to be made.

EEXXAAMMPPLLEE
       Typing the following at the command line: bblleenndd..sshh  aspect
       elevation 40 elev.asp

       will  create three new raster map layers named _e_l_e_v_._a_s_p_._r,
       _e_l_e_v_._a_s_p_._g, and _e_l_e_v_._a_s_p_._b,  that,  respectively,  contain
       40%  of	the red, green, and blue components of the _e_l_e_v_a_-
       _t_i_o_n map layer and contain 60% of the red, green, and blue
       components of the _a_s_p_e_c_t map layer.

FFIILLEESS
       This  program is simply a shell script.	Users are encour-
       aged to make their own shell scripts using  similar  tech-
       niques.	See $GISBASE/scripts/blend.sh.

SSEEEE AALLSSOO
       _r_._c_o_l_o_r_s,

       _r_._m_a_p_c_a_l_c

AAUUTTHHOORR
       Dave  Gerdes,  U.S.Army	Construction Engineering Research
       Laboratory

       _L_a_s_t _c_h_a_n_g_e_d_: _$_D_a_t_e_: _2_0_0_2_/_0_1_/_2_5 _0_5_:_4_5_:_3_2 _$



GRASS 5.0					      blend.sh(1)
