; The calc_grid_size script is used to calculate the grid dimensions with the given 
; two dimensional corner coordinates. The following arguments are inputs to the script
; 
; ul_x - The upper left x axis coordinate of the grid
; ul_y - The upper left y axis coordinate of the grid
; lr_x - The lower right x axis coordinate of the grid
; lr_y - The lower right y axis coordinate of the grid
; x_offset - The x axis origin value of the grid
; y_offset - The y axis origin value of the grid
; res - The resolution of the grid cells
; out_file_name_str - The file name to which the calculated parameters will be written to
;
; The input coordinates are adjusted to align to a grid which is based on the resolution 
; given to the script. With the adjusted corner coordinates the grid size is calculated.
;
; The output of this script is a file, and the file name is set the the variable 
; out_file_name_str. The following parameters are written to the file:
; ADJ_UL_X - The adjusted upper left x coordinate
; ADJ_LR_X - The adjusted lower right x coordinate
; ADJ_UL_Y - The adjusted upper left y coordinate
; ADJ_LR_Y - The adjusted lower right y cooridnate
; COLS - The number of columns of the grid. In other words, the grid width based on the 
;        resolution size
; ROWS - The number of rows of the grid. In other words, the grid length based on the 
;        resolution size
;
; Author: Willem.Marais@ssec.wisc.edu
; Date: 09/14/2012

PRO CALC_GRID_SIZE, UL_X, UL_Y, LR_X, LR_Y, X_OFFSET, Y_OFFSET, RES, OUT_FILE_NAME_STR

; switch_coord_bl = 0
; if ul_x GT lr_x then begin
;     ; The UL and LR coordinates are switched. This probably means that the corner coordinates 
;     ; are over the anti-meridian.
;     tmp_lr_x = lr_x
;     tmp_lr_y = lr_y
;     
;     lr_x = ul_x
;     lr_y = ul_y
;     
;     ul_x = tmp_lr_x
;     ul_y = tmp_lr_y
;     
;     switch_coord_bl = 1
; endif

res = double (res)

ul_x = double (ul_x) - double (x_offset)
lr_x = double (lr_x) - double (x_offset)

ul_y = double (ul_y) - double (y_offset)
lr_y = double (lr_y) - double (y_offset)

; Snap the coordinates to the grid based on the resolution value
ul_grid_x = ul_x / res ; Snap to the left
lr_grid_x = lr_x / res ; Snap to the left

lr_grid_y = lr_y / res ; Snap to the bottom
ul_grid_y = ul_y / res ; Snap to the bottom

; The projected UL longitude value is snapped to the left of the 
; 250m projection grid. If the UL longitude value is -180, the 
; snapped projected UL longitude will be less than the projected 
; value of -180. The following addition makes sure that the adjusted 
; UL longitude value does not exceed the -180 degree limit.
if ul_grid_x EQ 0 then $
    ul_grid_x = ul_grid_x + 1.0

; Caculate the grid size
if lr_grid_x GT ul_grid_x then begin
    x_grid_size = round (lr_grid_x - ul_grid_x)
endif else begin
    x_grid_size = round (ul_grid_x - lr_grid_x)
endelse

if ul_grid_y GT lr_grid_y then begin
    y_grid_size = round (ul_grid_y - lr_grid_y)
endif else begin
    y_grid_size = round (lr_grid_y - ul_grid_y)
endelse

; Caculate the adjusted coorner coordinates
adj_ul_x = ul_grid_x * res + x_offset
adj_lr_x = adj_ul_x + x_grid_size * res
;adj_lr_x = lr_grid_x * res + x_offset

adj_ul_y = ul_grid_y * res + y_offset
adj_lr_y = adj_ul_y - y_grid_size * res
;adj_lr_y = lr_grid_y * res + y_offset

; if switch_coord_bl GT 0 then begin
;     tmp_adj_lr_x = adj_lr_x
;     tmp_adj_lr_y = adj_lr_y
;     
;     adj_lr_x = adj_ul_x
;     adj_lr_y = adj_ul_y
;     
;     adj_ul_x = tmp_adj_lr_x
;     adj_ul_y = tmp_adj_lr_y
; endif

openw, lun, out_file_name_str, /get_lun
printf, lun, "ADJ_UL_X=", strcompress (string (long (adj_ul_x)), /remove_all)
printf, lun, "ADJ_LR_X=", strcompress (string (long (adj_lr_x)), /remove_all)
printf, lun, "ADJ_UL_Y=", strcompress (string (long (adj_ul_y)), /remove_all)
printf, lun, "ADJ_LR_Y=", strcompress (string (long (adj_lr_y)), /remove_all)
printf, lun, "COLS=", strcompress (string (long (x_grid_size)), /remove_all)
printf, lun, "ROWS=", strcompress (string (long (y_grid_size)), /remove_all)
free_lun, lun

END