; The GIMP -- an image manipulation program
; Copyright (C) 1995 Spencer Kimball and Peter Mattis
; 
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.  
; 
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
; 
; You should have received a copy of the GNU General Public License
; along with this program; if not, write to the Free Software
; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
;
;
; perspective-shadow.scm   version 1.2   2000/11/08
;
; Copyright (C) 1997-2000 Sven Neumann <sven@gimp.org>
; 
;  
; Adds a perspective shadow of the current selection or alpha-channel 
; as a layer below the active layer
;
  
(define (script-fu-perspective-shadow image
				      drawable
				      alpha
				      rel-distance
				      rel-length
				      shadow-blur
				      shadow-color
				      shadow-opacity
				      interpolation
				      allow-resize)
  (let* ((shadow-blur (max shadow-blur 0))
	 (shadow-opacity (min shadow-opacity 100))
	 (shadow-opacity (max shadow-opacity 0))
	 (rel-length (abs rel-length))
	 (alpha (* (/ alpha 180) *pi*))
	 (type (car (gimp-drawable-type-with-alpha drawable)))
	 (image-width (car (gimp-image-width image)))
	 (image-height (car (gimp-image-height image)))
	 (from-selection 0)
	 (active-selection 0)
	 (shadow-layer 0))
    
  (if (= rel-distance 0) (set! rel-distance 999999))

  (gimp-context-push)
  
  (gimp-image-undo-group-start image)
  
  (gimp-layer-add-alpha drawable)
  (if (= (car (gimp-selection-is-empty image)) TRUE)
      (begin
	(gimp-selection-layer-alpha drawable)
	(set! from-selection FALSE))
      (begin
	(set! from-selection TRUE)
	(set! active-selection (car (gimp-selection-save image)))))
  
  (let* ((selection-bounds (gimp-selection-bounds image))
	 (select-offset-x (cadr selection-bounds))
	 (select-offset-y (caddr selection-bounds))
	 (select-width (- (cadr (cddr selection-bounds)) select-offset-x))
	 (select-height (- (caddr (cddr selection-bounds)) select-offset-y))
 
	 (abs-length (* rel-length select-height))
	 (abs-distance (* rel-distance select-height))
	 (half-bottom-width (/ select-width 2))
	 (half-top-width (* half-bottom-width
			  (/ (- rel-distance rel-length) rel-distance)))
  
	 (x0 (+ select-offset-x (+ (- half-bottom-width half-top-width)
				 (* (cos alpha) abs-length))))
	 (y0 (+ select-offset-y (- select-height
				 (* (sin alpha) abs-length))))
	 (x1 (+ x0 (* 2 half-top-width)))
	 (y1 y0)
	 (x2 select-offset-x)
	 (y2 (+ select-offset-y select-height))
	 (x3 (+ x2 select-width))
	 (y3 y2)

	 (shadow-width (+ (- (max x1 x3) (min x0 x2)) (* 2 shadow-blur)))
	 (shadow-height (+ (- (max y1 y3) (min y0 y2)) (* 2 shadow-blur)))
	 (shadow-offset-x (- (min x0 x2) shadow-blur))
	 (shadow-offset-y (- (min y0 y2) shadow-blur)))
	 
  
    (set! shadow-layer (car (gimp-layer-new image
					    select-width
					    select-height
					    type
					    "Perspective Shadow"
					    shadow-opacity
					    NORMAL-MODE)))


    (gimp-image-add-layer image shadow-layer -1)
    (gimp-layer-set-offsets shadow-layer select-offset-x select-offset-y)
    (gimp-drawable-fill shadow-layer TRANSPARENT-FILL)
    (gimp-context-set-background shadow-color)
    (gimp-edit-fill shadow-layer BACKGROUND-FILL)
    (gimp-selection-none image)

    (if (= allow-resize TRUE)
	(let* ((new-image-width image-width)
	       (new-image-height image-height)
	       (image-offset-x 0)
	       (image-offset-y 0))

	  (if (< shadow-offset-x 0)
	      (begin
		(set! image-offset-x (- 0 shadow-offset-x))
		(set! new-image-width (- new-image-width image-offset-x))))

	  (if (< shadow-offset-y 0)
	      (begin
		(set! image-offset-y (- 0 shadow-offset-y))
		(set! new-image-height (- new-image-height image-offset-y))))
	  
	  (if (> (+ shadow-width shadow-offset-x) new-image-width)
	      (set! new-image-width (+ shadow-width shadow-offset-x)))
	  
	  (if (> (+ shadow-height shadow-offset-y) new-image-height)
	      (set! new-image-height (+ shadow-height shadow-offset-y)))
	  (gimp-image-resize image
			     new-image-width
			     new-image-height
			     image-offset-x
			     image-offset-y)))
  
    (gimp-drawable-transform-perspective shadow-layer
					 x0 y0
					 x1 y1
					 x2 y2
					 x3 y3
					 TRANSFORM-FORWARD interpolation
					 TRUE 3 FALSE)

    (if (>= shadow-blur 1.0)
	(begin
	  (gimp-layer-set-preserve-trans shadow-layer FALSE)
	  (gimp-layer-resize shadow-layer
			     shadow-width
			     shadow-height
			     shadow-blur
			     shadow-blur)
	  (plug-in-gauss-rle 1
			     image
			     shadow-layer
			     shadow-blur
			     TRUE
			     TRUE))))

  (if (= from-selection TRUE)
      (begin
	(gimp-selection-load active-selection)
	(gimp-edit-clear shadow-layer)
	(gimp-image-remove-channel image active-selection)))

  (if (and
       (= (car (gimp-layer-is-floating-sel drawable)) 0)
       (= from-selection FALSE))
      (gimp-image-raise-layer image drawable))

  (gimp-image-set-active-layer image drawable)
  (gimp-image-undo-group-end image)
  (gimp-displays-flush)

  (gimp-context-pop)))

(script-fu-register "script-fu-perspective-shadow"
		    _"_Perspective..."
		    "Add a perspective shadow"
		    "Sven Neumann <sven@gimp.org>"
		    "Sven Neumann"
		    "2000/11/08"
		    "RGB* GRAY*"
		    SF-IMAGE       "Image"          0
		    SF-DRAWABLE    "Drawable"       0
		    SF-ADJUSTMENT _"Angle"          '(45 0 180 1 10 1 0)
		    SF-ADJUSTMENT _"Relative distance of horizon" '(5 0 24 .1 1 1 1)
		    SF-ADJUSTMENT _"Relative length of shadow" '(1 0 24 .1 1 1 1)
		    SF-ADJUSTMENT _"Blur radius"    '(3 0 1024 1 10 0 0)
		    SF-COLOR      _"Color"          '(0 0 0)
		    SF-ADJUSTMENT _"Opacity"        '(80 0 100 1 10 0 0)
		    SF-OPTION     _"Interpolation"  '(_"None" _"Linear" _"Cubic")
		    SF-TOGGLE     _"Allow resizing" FALSE)

(script-fu-menu-register "script-fu-perspective-shadow"
			 _"<Image>/Filters/Shadowplug/Shadows")
