Line Drawing Algorithm

Hi Experts!

I Want To Write a Procedure That Draws a Line In Graphic Mode 640x480.
I Know That TP7.0 Has This Procedure in Graph.tpu But Because I'm Writing My New OS With Assembly,So I Have To Write a New Proc For Drawing Line.

I Have Read Bresenham's Line Algorithm But It Has a Lot Of Problems Like:
When Y is bigger then X The Procedure Draws Just a Straight Line.

Please Help Me.
(USE PUTPIXEL IN YOUR EXAMPLE)

Bye
Programmer-x
 
LVL 15
Hamidreza VakilianSenior iOS/Android DeveloperAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

MrT-RSICommented:
 procedure line(x1,y1,x2,y2 : integer;color : byte);
  var
    x21l,y21l,d1xl,d1yl,d2xl,d2yl,max21l,min21l,duml,loopl : integer;
  begin
    x21l := x2 - x1;
    y21l := y2 - y1;
    d1xl := sign(x21l);
    d1yl := sign(y21l);
    d2xl := d1xl;
    d2yl := 0;
    max21l := abs(x21l);
    min21l := abs(y21l);
    if max21l < min21l then begin
      d2xl := 0;
      d2yl := d1yl;
      duml := max21l; max21l := min21l; min21l := duml;
    end;
    duml := max21l shr 1;
    for loopl := 0 to max21l do begin
      putpixel(x1,y1,color);
      duml := duml + min21l;
      if duml >= max21l then begin
        duml := duml - max21l;
        x1 := x1 + d1xl;
        y1 := y1 + d1yl;
      end else begin
        x1 := x1 + d2xl;
        y1 := y1 + d2yl;
      end;
    end;
  end;

with

  function sign(a : integer) : integer; external;
    { Returns the sign of value a (negative: -1, positive: 1, zero: 0).      }

in 32 bit asm:

  sign proc near a : word
    cmp a,0
    setg al ;al = 1 if a > 0
    setl ah ;ah = 1 if a < 0
    sub al,ah ;-1 if a < 0, 0 if a = 0, 1 if a > 0
    cbw ;return an integer
    ret
  sign endp

This has a own putpixel, which also includes color, just remove the color param for normal putpixel.

Good luck,

- Rob.
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Hamidreza VakilianSenior iOS/Android DeveloperAuthor Commented:
Hi MrT-RSI!

Thanks For Your Code.
Can You Convert it To Assembly?
If You Do That,I Will Give 50 Points More.

Bye
Programmer-x
0
Cloud Class® Course: C++ 11 Fundamentals

This course will introduce you to C++ 11 and teach you about syntax fundamentals.

HypoCommented:
I have an almost complete graphicengine/unit that you can use if you like, I wanted to use graphic
functions that were very optimized for speed in the graphicmodes I wanted to use...
so most of the routines I wrote in assembler and optimized them for mode 13 and
some other Vesa 2.0 modes,

/Hypo
0
MrT-RSICommented:
make that 150 and I'll do it !
0
Hamidreza VakilianSenior iOS/Android DeveloperAuthor Commented:
Hi MrT-RSI!

All Right.I Have Converted It To Assembler,But It Has Some Errors When I Use it In My Program.If You Tell What I'm Doing Wrong I Will Give You That 50 Points More.(50+50=100)
**************************************************************
LINE      MACRO      X1,Y1,X2,Y2
LOCAL      CON1,CON2,OK,IF1,IF2,FIN
X21      DW      0
Y21      DW      0
D1X      DW      0
D1Y      DW      0
D2X      DW      0
D2Y      DW      0
MAX21      DW      0
MIN21      DW      0
DUM      DW      0
X      DW      X1
Y      DW      Y1
XX      DW      X2
YY      DW      Y2
PUSHA

MOV      AX,XX
SUB      AX,X
MOV      X21,AX

MOV      AX,YY
SUB      AX,Y
MOV      Y21,AX

SIGN      X21
MOV      D1X,AX

SIGN      Y21
MOV      D1Y,AX

MOV      AX,D1X
MOV      D2X,AX

MOV      D2Y,0

ABS      X21      
MOV      MAX21,AX

ABS      Y21
MOV      MIN21,AX

MOV      AX,MAX21

CMP      AX,MIN21
JL      CON1

JMP      OK

CON1:
MOV      D2X,0
MOV      AX,D1Y
MOV      D2Y,AX

MOV      AX,MAX21
MOV      DUM,AX

MOV      AX,MIN21
MOV      MAX21,AX

MOV      AX,DUM
MOV      MIN21,AX

OK:

MOV      AX,MAX21
SHR      AX,1
MOV      DUM,AX

MOV      CX,MAX21

CON2:            

PIXEL      X,Y

MOV      AX,DUM
ADD      AX,MIN21
MOV      DUM,AX

CMP      AX,MAX21
JGE      IF1
JMP      IF2

IF1:
MOV      AX,DUM
SUB      AX,MAX21
MOV      DUM,AX

MOV      AX,X
ADD      AX,D1X
MOV      X,AX

MOV      AX,Y
ADD      AX,D1Y
MOV      Y,AX

JMP      FIN

IF2:
MOV      AX,X
ADD      AX,D2X
MOV      X,AX

MOV      AX,Y
ADD      AX,D2Y
MOV      Y,AX

FIN:
LOOP      CON2      

POPA
ENDM
**************************************************************
Best Wishes...
Programmer-x
0
Hamidreza VakilianSenior iOS/Android DeveloperAuthor Commented:
Hi MrT-RSI!

I Understood My Problem.I Converted It To ASM and It Works Very Good...

Best Wishes...
Programmer-x
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Pascal

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.