; GIF LITE v2.0 by Willow
; Written in pure assembler by Ivushkin Andrey aka Willow
;
; This include file will contain functions to handle GIF image format
;
; Created: August 15, 2004
; Last changed: September 9, 2004
; Change COLOR_ORDER in your program
; if colors are displayed improperly
COLOR_ORDER equ MENUETOS
if ~ (COLOR_ORDER in <MENUETOS,OTHER>)
; This message may not appear under MenuetOS, so watch...
display 'Please define COLOR_ORDER: MENUETOS or OTHER',13,10
end if
; virtual structure, used internally
struc GIF_list
{
.NextImg rd 1
.Left rw 1
.Top rw 1
.Width rw 1
.Height rw 1
}
struc GIF_info
{
.Left rw 1
.Top rw 1
.Width rw 1
.Height rw 1
}
_null fix 0x1000
; ****************************************
; FUNCTION GetGIFinfo - retrieve Nth image info
; ****************************************
; in:
; esi - pointer to image list header
; ecx - image_index (0...img_count-1)
; edi - pointer to GIF_info structure to be filled
; out:
; eax - pointer to RAW data, or 0, if error
GetGIFinfo:
push esi ecx edi
xor eax,eax
jecxz .eloop
.lp:
mov esi,[esi]
test esi,esi
jz .error
loop .lp
.eloop:
add esi,4
movsd
movsd
mov eax,esi
.error:
pop edi ecx esi
ret
; ****************************************
; FUNCTION ReadGIF - unpacks GIF image
; ****************************************
; in:
; esi - pointer to GIF file in memory
; edi - pointer to output image list
; eax - pointer to work area (MIN 16 KB!)
; out:
; eax - 0, all OK;
; eax - 1, invalid signature;
; eax >=8, unsupported image attributes
;
; ecx - number of images
ReadGIF:
push esi edi
mov [.table_ptr],eax
mov [.cur_info],edi
xor eax,eax
mov [.globalColor],eax
mov [.img_count],eax
inc eax
cmp dword[esi],'GIF8'
jne .er ; signature
mov ecx,[esi+0xa]
inc eax
add esi,0xd
mov edi,esi
bt ecx,7
jnc .nextblock
mov [.globalColor],esi
call .Gif_skipmap
.nextblock:
cmp byte[edi],0x21
jne .noextblock
inc edi
cmp byte[edi],0xf9 ; Graphic Control Ext
jne .no_gc
add edi,7
jmp .nextblock
.no_gc:
cmp byte[edi],0xfe ; Comment Ext
jne .no_comm
inc edi
.block_skip:
movzx eax,byte[edi]
lea edi,[edi+eax+1]
cmp byte[edi],0
jnz .block_skip
inc edi
jmp .nextblock
.no_comm:
cmp byte[edi],0xff ; Application Ext
jne .nextblock
add edi,13
jmp .block_skip
.noextblock:
cmp byte[edi],0x2c ; image beginning
jne .er
inc [.img_count]
inc edi
mov esi,[.cur_info]
add esi,4
xchg esi,edi
movsd
movsd
push edi
movzx ecx,word[esi]
inc esi
bt ecx,7
jc .uselocal
push [.globalColor]
mov edi,esi
jmp .setPal
.uselocal:
call .Gif_skipmap
push esi
.setPal:
movzx ecx,byte[edi]
inc ecx
mov [.codesize],ecx
dec ecx
pop [.Palette]
lea esi,[edi+1]
mov edi,[.table_ptr]
xor eax,eax
cld
lodsb ; eax - block_count
add eax,esi
mov [.block_ofs],eax
mov [.bit_count],8
mov eax,1
shl eax,cl
mov [.CC],eax
inc eax
mov [.EOI],eax
lea ecx,[eax-1]
mov eax, _null shl 16
.filltable:
stosd
inc eax
loop .filltable
pop edi
mov [.img_start],edi
.reinit:
mov edx,[.EOI]
inc edx
push [.codesize]
pop [.compsize]
call .Gif_get_sym
cmp eax,[.CC]
je .reinit
call .Gif_output
.cycle:
movzx ebx,ax
call .Gif_get_sym
cmp eax,edx
jae .notintable
cmp eax,[.CC]
je .reinit
cmp eax,[.EOI]
je .end
call .Gif_output
.add:
push eax
mov eax,[.table_ptr]
mov [eax+edx*4],ebx
pop eax
cmp edx,0xFFF
jae .cycle
inc edx
bsr ebx,edx
cmp ebx,[.compsize]
jne .noinc
inc [.compsize]
.noinc:
jmp .cycle
.notintable:
push eax
mov eax,ebx
call .Gif_output
push ebx
movzx eax,bx
call .Gif_output
pop ebx eax
jmp .add
.er:
pop edi
jmp .ex
.end:
mov eax,[.cur_info]
mov [eax],edi
mov [.cur_info],edi
add esi,2
xchg esi,edi
.nxt:
cmp byte[edi],0
jnz .continue
inc edi
jmp .nxt
.continue:
cmp byte[edi],0x3b
jne .nextblock
xor eax,eax
stosd
mov ecx,[.img_count]
.ex:
pop edi esi
ret
.Gif_skipmap:
; in: ecx - image descriptor, esi - pointer to colormap
; out: edi - pointer to area after colormap
and ecx,111b
inc ecx ; color map size
mov ebx,1
shl ebx,cl
lea ebx,[ebx*2+ebx]
lea edi,[esi+ebx]
ret
.Gif_get_sym:
mov ecx,[.compsize]
push ecx
xor eax,eax
.shift:
ror byte[esi],1
rcr eax,1
dec [.bit_count]
jnz .loop1
inc esi
cmp esi,[.block_ofs]
jb .noblock
push eax
xor eax,eax
lodsb
test eax,eax
jnz .nextbl
mov eax,[.EOI]
sub esi,2
add esp,8
jmp .exx
.nextbl:
add eax,esi
mov [.block_ofs],eax
pop eax
.noblock:
mov [.bit_count],8
.loop1:
loop .shift
pop ecx
rol eax,cl
.exx:
xor ecx,ecx
ret
.Gif_output:
push esi eax edx
mov edx,[.table_ptr]
.next:
push word[edx+eax*4]
mov ax,word[edx+eax*4+2]
inc ecx
cmp ax,_null
jnz .next
shl ebx,16
mov bx,[esp]
.loop2:
pop ax
lea esi,[eax+eax*2]
add esi,[.Palette]
if COLOR_ORDER eq MENUETOS
mov esi,[esi]
bswap esi
shr esi,8
mov [edi],esi
add edi,3
else
movsw
movsb
end if
loop .loop2
pop edx eax esi
ret
.globalColor rd 1
.img_count rd 1
.cur_info rd 1 ; image table pointer
.img_start rd 1
.codesize rd 1
.compsize rd 1
.bit_count rd 1
.CC rd 1
.EOI rd 1
.Palette rd 1
.block_ofs rd 1
.table_ptr rd 1