OpenEuphoria

Re: BitBlt

• Posted by David Cuny <dcuny at LANSET.COM> Nov 02, 1998
• 486 views

John DeHope wrote:

>First off you need a generic blitting procedure, which is basically a
>wrapper for EMemCopy.

I would *love* to have a general blitter for Euphoria - especially one that
handles all the graphics modes!

But from my ancient experiments with trying to turn EMemCopy into a general
blitter, it seemed that it was limited in the number of graphic modes it
addressed, and didn't work in the ones I care about. This seems to be
confirmed by Jiri's comments.

I've *whined* for Robert to add a blitter to Euphoria, and for Pete to
*pleeeze* code me up one in assembly...

I put together a generic blitter (included), but it's obviously slow. WinMan
was based on an optimized version of this blitter, that understood 0 in the
argument to be a screen, and handled clipping better. However, this version
*is* generic.

I'd love to see a generic blitter added to the core Euphoria routines.

-- David Cuny

-- generic bit blitter
global constant
    CopyROP     = 1,    -- dst = src
    OrROP       = 2,    -- dst = dst OR src
    XorROP      = 3,    -- dst = dst XOR src
    EraseROP    = 4,    -- dst = (NOT src) AND dst
    NotCopyROP  = 5,    -- dst = NOT src
    NotOrROP    = 6,    -- dst = (NOT src) OR dst
    NotXorROP   = 7,    -- dst = (NOT src) XOR dst
    NotEraseROP = 8,    -- dst = src AND dst
    NotROP      = 9     -- dst = NOT dst

function opPixels( integer rop, integer src, integer dst )
    if    rop = CopyROP     then return src
    elsif rop = OrROP       then return or_bits(dst, src)
    elsif rop = XorROP      then return xor_bits(dst, src)
    elsif rop = EraseROP    then return and_bits( not(src), dst)
    elsif rop = NotCopyROP  then return not(src)
    elsif rop = NotOrROP    then return or_bits(not(src), dst)
    elsif rop = NotXorROP   then return xor_bits(not(src), dst)
    elsif rop = NotEraseROP then return and_bits(src, dst)
    elsif rop = NotROP      then return not(dst)
    end if
    -- error: unspecified rop code

end function

global function bitBlt( sequence dst, integer dx, integer dy,
                        sequence src, integer sx, integer sy,
                            integer sw, integer sh, integer rop )
    -- this function copies a block of pixels from one bitmap to
    -- another. bitBlt means bit block transfer.
    -- arguments:
    --
    --  dst     the device to copy to
    --  dx, dy  the position to copy to
    --  src     the device to copy from
    --  sx, sy  the position to copy from
    --  sw, sh  the width and height of the block to be copied
    --  rop     raster operation to be used when doing copying
    --

    -- this can obviously be specialized to operate *much* faster

    -- avoid lots of -1's in the calculations
    dx = dx - sx
    dy = dy - sy
    sh = sh - 1
    sw = sw - 1

    for y = sy to sy+sh do
        for x = sx to sx+sw do
            dst[dy+y][dx+x] = opPixels( rop, src[y][x], dst[dy+y][dx+x] )
        end for
    end for

    return dst

end function