Last Updated or created 2023-10-05

(NOTE, Dosbox can’t cope with the register speed, use real HW or PCem)

Generating a RAW image and Palette, a in a new way

This bash script to convert BMP to Raw and a compiled colorpalette.
(Note: this converts to 8 bit depth, the assembly code in the final assemby program converts to 6 for VGA mode 13h

So this time, i won´t have to use the standard VGA palette as mentioned in previous posts.
(Gimp colors > indexed (255 colors) ; save as BMP, exclude colorspace information)

I’m using identify to extract the colorpalette, which i’m converting to DB entries for the fasm compiler

#!/bin/bash
if [ $# -lt 1 ] ; then
	echo "$0 filename"
	exit 0
fi
size=$(stat $1 | grep Size | awk '{ print $2 }')
skipsize=$(( $size - 64000))
dd if=$1 of=$1.raw skip=$skipsize bs=1

identify -verbose $1 | awk '/Colormap:/,/Rendering/' | grep -v Colormap | grep -v Rendering | awk '{ print $2 } ' | tr -d '()' | while read ; do echo "db $REPLY" ;done > data.asm
fasm data.asm

Code

use16
org 0x100

; variables
CRTC_INDEX = 0x03D4
CRTC_DATA = 0x03D5
INPUT_STATUS = 0x03DA
HRETRACE = 0x01
VRETRACE = 0x03 ; bit 3 =8 ?
MAXIMUM_SCAN_LINE = 0x09
LINE_OFFSET = 0x13

; bar
upperbar = 1
lowerbar = 399

jmp start
; memory locations for data
updown dw 1
direction DB 0
filename DB "firework.raw",0
oldline db 0


start:
; set mode 320x200 256 colors palette
	mov ah,0x0
	mov al,13h
	int 10h

; clear screen routine, not really needed
clearscreen:
	push ax
	mov ax, 0a000h
	mov es, ax
	pop ax
	xor di, di
	inc ax
	mov cx, 64000 ; 320x200
	rep stosb
; set colors
; call file loader 
	call Loadfile
	call setpalette

; Move loaded file to Screen memory
	mov ax,0a000h
	mov es,ax
	mov ax,6000h
	mov ds,ax
	mov si,0
	mov di,0
	mov cx,320*200/2
	rep movsw

	push cs
	pop ds

;	store org effect2 values
	mov dx, CRTC_INDEX
	mov al,LINE_OFFSET
	out dx,al
	mov dx, CRTC_DATA
	in al,dx
	mov [oldline],al


; after displaying the image or displaying an error, wait for keypress to exit
waitforkeyloop:
	call effect 	; Calling the effect
	MOV AH,1
	INT 16h
	JZ waitforkeyloop
	XOR AH,AH
	INT 16h
Exit:
	MOV AX,3	; default text mode 3
	INT 10h
	MOV AX,4C00h	; exit to dos (terminate process)
	INT 21h
; loop ends here

; Loads raw 64000 bytes image to screen memory
Loadfile:
	push ds
	MOV DX,filename
	MOV AX,3D00h	; open filehandle
	INT 21h
	JC Err1
	MOV BX,AX   	; filehandle
	MOV CX,64000
	mov dx,06000h 	; destination 0000:a000h - Screen memory
	mov ds,dx
	MOV DX,0
	MOV AH,3Fh	; read from file
	INT 21h
	JC  Err1
	MOV AH,3Eh	; close filehandle
	INT 21h
	pop ds
RET

; print error
Err1:
	push cs		; make ds same as cs
	pop ds
	MOV AX,3	; default text mode 3
	INT 10h
	MOV DX,TxtErr1	; error
	MOV AH,09h
	INT 21h
	RET

effect:
	cli		; stop interrupts
	call waitvretrace	; wait for vertical retrace

; gets start scanline and direction
	mov ax,[updown]
	mov cl,[direction]
	cmp cl,0		; 0 move down
	jz	addcounter
	dec ax
	dec ax
	cmp ax,upperbar  	; reached upper bar ?
	jnz gohere ; jnz
	mov cl,0
	mov [direction],cl
	jmp gohere
addcounter:
	inc ax
	inc ax
	cmp ax,lowerbar		; reached bottom bar?
	jnz gohere 	;jnz
	mov cl,1		; change direction
	mov [direction],cl
gohere:
	mov [updown],ax		; store new location

; al = scanline, call wait for scanline
	call longwaithretrace
; other effect
        mov dx, CRTC_INDEX
        mov al, LINE_OFFSET
        out dx,al
        mov dx, CRTC_DATA
        mov al, 0
        out dx,al


; wait scanlines (height of bar)
	mov ax,400
	mov cx,[updown]
	sub ax,cx
	call longwaithretrace

; restore effect2
        mov dx, CRTC_INDEX
        mov al, LINE_OFFSET
        out dx, al
        mov dx, CRTC_DATA
        mov al, [oldline]
        out dx,al
		
	sti	; start interrupts again
	ret

; routine that fixes 8 to 6 bits and sets palette
setpalette:
	; 8 bits to 6 
	mov si,coltab
	mov cx,256*3
	rest:
		mov al,[si]
		shr al,2
		mov [si],al
		dec cx
		inc si
		cmp cx,0
		jnz rest
; now set colors
	mov dx,3c8h
	xor al,al
	out dx,al
	inc dx
	mov si,coltab
	mov cx,256*3
	rep outsb
ret


; this waits for vertical retrace
waitvretrace:
	mov dx,INPUT_STATUS
	waitv1:
		in al,dx
		test al,8
		jnz waitv1
	waitv2:
		in al,dx
		test al,8
		jz waitv2
ret

; routine that waits for horizontal retrace
waithretrace:
	mov cl,al
	mov dx,INPUT_STATUS
	waith1:
		in al,dx
		test al,1
		jnz waith1
	waith2:
		in al,dx
		test al,1
		jz waith2
		dec cl
		cmp cl,0
		jnz waith1
ret

longwaithretrace:
	mov cx,ax
	mov dx,INPUT_STATUS
	lwaith1:
		in al,dx
		test al,1
		jnz lwaith1
	lwaith2:
		in al,dx
		test al,1
		jz lwaith2
		dec cx
		cmp cx,0
		jnz lwaith1
ret
TxtErr1 DB "firework.raw not found!",7,10,13,"$"

coltab: 
include 'data.asm'