Q: BP7+ASM

antispam.pl...@siemens.at (Gerd)

Delphi Developer

Wed, 18 Jun 1902 08:00:00 GMT

Q: BP7+ASM

{
Hi ASM gurus
I want draw a Gouraud-shaded horizontal line.
But there is a little problem in this procedure,
if C2 is greater 127 (see example output).
Please can you tell me what's wrong ?
Do you know a correct solution ?
THANX a lot ;-) Gerd

Quote

}

uses crt;

const segPage: word=$A000;

{c1: color index of 1.pixel
c2: color index if last pixel}
procedure _GouraudHLineAsm (x1,x2, y, c1,c2: word); Assembler;

asm
mov cx,X2
inc cx
sub cx,X1 {cx = (X2-X1+1)}
jle @fin {if x2+1 <= x1 goto fin}
mov ax,Y
shl ax,6
mov bx,ax
shl ax,2
add bx,ax
add bx,X1
mov di,bx {di = Y*320+X1}
mov es,segPage {es = seg(page256^)}
mov bx,C1
mov ax,C2
sub ax,bx
shl ax,8 {ax = (C2-C1) shl 8}
cwd
idiv cx {ax = ax/cx}
shl bx,8 {bx = C1 shl 8}
shr cx,1 {cx = cx/2}
jnz @next {if cx <> 0 goto next}
mov es:[di],bh
jmp @fin
@next:
jnc @loop
mov es:[di],bh
add bx,ax {bx += ax}
inc di
@loop:
mov dl,bh {dl = bh}
add bx,ax {bx += ax}
mov dh,bh {dh = bh}
add bx,ax {bx += ax}
mov es:[di],dx
inc di
inc di
dec cx
jnz @loop
@fin:
end;

var y: integer;
begin
asm mov ax,19;int 16; end;
for y := 0 to 199
do _GouraudHLineAsm (y div 3, 319-(y div 3), y, 17,56+y);
readkey;
TextMode(3);
end.