#!/usr/bin/env gimp-script-fu-interpreter-3.0

; Script-Fu script for GIMP 3 that exports the current image to valid GoldSrc
; (Half-Life 1) texture format. It resizes to 256x256 or 512x512 if needed,
; changes the precision to 8-bit integer, converts it to indexed mode with
; optimum palette generation, then exports it to BMP without writing color space
; information.

; Usage:
;     To install it, copy it to your GIMP scripts folder (see which one(s) in
;     Edit->Preferences->Folders->Scripts) and restart the program. Then, open
;     the image you want to export and run Filters->Custom->GoldSrc Export...


(define (script-fu-goldsrc-export image drawables size_small)
	; GIMP 3-only script.
	(script-fu-use-v3)

	(let* (
		; Compose the new BMP export filename from the original image. This
		; procedure will return %NULL if not loaded/imported/saved/exported yet.
		(old_filename (gimp-image-get-file image))
		(new_filename (if (or (equal? old_filename '()) (equal? old_filename ""))
			; A newly created image, unsaved. Append the extension to the name.
			(string-append (gimp-image-get-name image) ".bmp")
			; An existing image. Replace the file extension. NOTE: this will not
			; work with extensions different than 3 characters!
			(string-append (substring old_filename 0 (- (string-length old_filename) 4)) ".bmp")))
		(max_size (if (eq? size_small TRUE) 256 512)))

		; Resize the image if bigger than 256x256 (small) or 512x512 (large).
		(let* ((width (gimp-image-get-width image))
			   (height  (gimp-image-get-height image)))
			(when (or (> width max_size) (> height max_size))
				(let* ((scale_factor (min (/ max_size width) (/ max_size height))))
					(gimp-image-scale image (* scale_factor width) (* scale_factor height))
				)
			)
		)

		; Change precision to 8-bit integer (if not already so).
		(let* ((current_precision (gimp-image-get-precision image)))
			(when (not (= current_precision PRECISION-U8-NON-LINEAR))
				(gimp-image-convert-precision image PRECISION-U8-NON-LINEAR)
			)
		)

		; Convert image to indexed mode, generating optimum palette.
		(let* ((base_type (gimp-image-get-base-type image)))
			(when (not (= base_type INDEXED))
				(gimp-image-convert-indexed image CONVERT-DITHER-FS-LOWBLEED CONVERT-PALETTE-GENERATE 256 #t #t "")
			)
		)

		; Export as BMP, without writing color space information.
		(file-bmp-export RUN-NONINTERACTIVE image new_filename '() #f #f "rgb-888")
		(gimp-displays-flush)
	)
)


(script-fu-register-filter
	"script-fu-goldsrc-export"                                    ; Procedure name.
	"GoldSrc Export..."                                           ; Menu label.
	"Export image to valid GoldSrc (Half-Life 1) texture format." ; Description.
	"DaSalba"                                                     ; Author.
	"Copyright (c) 2025 DaSalba. MIT License."                    ; Copyright notice.
	"March 26, 2025"                                              ; Date created.
	"*"                                                           ; Image type that the script works on.
	SF-ONE-DRAWABLE                                               ; This plugin works with only one image/layer.
	SF-TOGGLE       "S_mall size (256x256)?" FALSE                ; Single parameter, if TRUE image will be max 256x256 instead of 512x512.
)

(script-fu-menu-register "script-fu-goldsrc-export" "<Image>/Filters/Custom")