OpenEuphoria

Re: xor_line

• Posted by jiri babor <jbabor at PARADISE.NET.NZ> Oct 25, 1998
• 501 views

Sorry, Hawke, I should not rely on my memory that much, it's like a
sieve. I just checked the archive version of rat.e, and you are right,
the xor library is not there. I completely forgot I had not released
the complete widget set with the ratpack, just a cut-down version, in
other words only the routines necessary for the demo (I think, Irv had
already been pushing his 'windoz', and I did not want to create unfair
competition).

If you still want to compare notes, or for anybody else possibly
interested, the routine is attached below.

Sorry again, but I told you to give me a yell, if you strike a
problem..  jiri


global procedure xor_line(integer c, sequence p)
    -- c is line color - same usage as draw_line, but limited
    -- to single line segment between 2 points in sequence p
    integer ai,bi,d,x,y,x2,y2,xi,yi,dx,dy
    p=floor(p)
    x=p[1][1]
    x2=p[2][1]
    y=p[1][2]
    y2=p[2][2]
    if y=y2 then        -- horizontal line
        if x<x2 then
            pixel(xor_bits(get_pixel({x,y,x2-x+1}),repeat(c,x2-x+1)),{x,y})
        else

        end if
    elsif x=x2 then     -- vertical line
        if y<y2 then
            for i=y to y2 do
                pixel(xor_bits(get_pixel({x,i}),c),{x,i})
            end for
        else
            for i=y2 to y do
                pixel(xor_bits(get_pixel({x,i}),c),{x,i})
            end for
        end if
    else
        if x<x2 then
            xi=1
            dx=x2-x
        else
            xi=-1
            dx=x-x2
        end if
        if y<y2 then
            yi=1
            dy=y2-y
        else
            yi=-1
            dy=y-y2
        end if
        pixel(xor_bits(get_pixel({x,y}),c),{x,y})
        if dx>dy then
            ai=2*(dy-dx)
            bi=2*dy
            d=bi-dx
            while x!=x2 do
                if d>=0 then
                    y=y+yi
                    d=d+ai
                else
                    d=d+bi
                end if
                x=x+xi
                pixel(xor_bits(get_pixel({x,y}),c),{x,y})
            end while
        else
            ai=2*(dx-dy)
            bi=2*dx
            d=bi-dy
            while y!=y2 do
                if d>=0 then
                    x=x+xi
                    d=d+ai
                else
                    d=d+bi
                end if
                y=y+yi
                pixel(xor_bits(get_pixel({x,y}),c),{x,y})
            end while
        end if
    end if
end procedure -- xor_line

global procedure xor_draw_line(integer c, sequence p)
    -- same usage as draw_line: c is line color, p is sequence of
    -- points ({x,y} coordinates) to be connected
    -- works ok for single line segments, but xor_line() above is faster
    for i=1 to length(p)-1 do xor_line(c,p[i..i+1]) end for
    -- compensate for cancellations at line joints
    for i=2 to length(p)-1 do pixel(xor_bits(get_pixel(p[i]),c),p[i]) end
for
    -- compensate for cancellation at closure for line loops
    if not compare(p[1],p[length(p)]) then
        pixel(xor_bits(get_pixel(p[1]),c),p[1])
    end if
end procedure

-----Original Message-----
From: Hawke <mdeland at NWINFO.NET>
To: EUPHORIA at LISTSERV.MUOHIO.EDU <EUPHORIA at LISTSERV.MUOHIO.EDU>
Date: Sunday, October 25, 1998 3:03 PM
Subject: Re: truecolr.e update, line(), other stuff...


>jiri babor wrote:
>>Go to the Archives and fetch my ratpack (SVGA mouse routines).
>>In it you will find a little library called xor.e.
>>From memory, among other graphic elements it also contains
>>an xor_line routine.
>ummm... i looked all thru all the files in rat.zip and i
>couldn't find xor_line.  i looked pretty thoroughly...
>
>>It is based on Bresenham's line algorithm,
>knowing this however, i was able to find that algorithm
>and implement it (it's pretty quick),
>so thankee! for the tip... :)
>
>--Hawke'
>