MULPIX D,{#}S Syntax question
Bob Drury
Posts: 236
in Propeller 2
if D=d4d3d2d1 and S =s3s2s1s0 then Multipy DxS by should be d3=d3s3 d2=d2s2 d1=d1s1 d0=d0s0
but that doeesn' happen and the nomenclature $FF = 1.0 and $00= 0.0 I am not sure what that means
the ADDPIx d3= d3+s3 d2=d2+s2 d1= d1+s1 d0 = d0+s0 works so not sure what MULPIX is doing
Regards
Bob (WRD)
Comments
What result are you expecting, and what are you seeing?
From the instruction description, with $FF = 1.0 and $00 = 0.0 then with D of $0080FFFF and S of $008080FF I would expect a result of something like $004080FF.
That’s:
$00 x $00 = 0.0 x 0.0 = 0.0 = $00
$80 x $80 = 0.5 x 0.5 = 0.25 = $40
$80 x $FF = 0,5 x 1.0 = 0.5 = $80
$FF x $FF = 1.0 x 1.0 = 1.0 = $FF
I’m not in a position to test my interpretation.
AJL
Will test.
Thanks
Bob (WRD)
It's multiplying with scaling, maybe SCLPIX, or SCAPIX would have been a better name.
So if D=d3d2d1d0 and S=s3s2s1s0 the result should be:
d3 = d3*s3/255 d2 = d2*s2/255 d1 = d1*s1/255 d0 = d0*s0/255Andy
AJL
Tested and you are correct. Thanks
Ariba
I will modify notes about scaling and rounding to bit
Regards
Bob (WRD)
Glad to be of assistance :-)
I didn't know about mulpix, and I'm glad you pointed it out. I had this routine in my pixel driver which is a direct port from the P1.
pub colorx(r, g, b, w, level) : result | m '' Packs r-g-b-w bytes into long '' -- r, g, b, and w are element levels, 0..255 '' -- level is brightness, 0..255 (0..100%) if (level <= 0) result := $00_00_00_00 elseif (level >= 255) result := color(r, g, b, w) else r := r * level / 255 ' apply level to rgbw g := g * level / 255 b := b * level / 255 w := w * level / 255 result := color(r, g, b, w)I upgraded the method in my P2 object to this, and save a little more than 9 microseconds at 200MHz.
pub p2_colorx(r, g, b, w, level) : result '' Packs r-g-b-w bytes into long '' -- r, g, b, and w are element levels, 0..255 '' -- level is brightness, 0..255 (0..100%) org cmps level, #0 wcz ' at or below 0? if_be jmp #.done ' yes, done setbyte result, r, #3 ' make 32-bit color setbyte result, g, #2 setbyte result, b, #1 setbyte result, w, #0 cmps level, #255 wcz ' at or above 255? if_ae jmp #.done ' yes, done rep #1, #3 ' make multiplier rolbyte level, level, #0 mulpix result, level ' scale the color .done endrep #1, #3 ' make multiplier rolbyte level, level, #0You can do this to the same effect:
movbyts level, #%%0000Or, alternatively, instead of
movbyts level, #%%0000 mulpix result,levelyou can use
setpiv level blnpix result,#0Thank you!