Any suggestions on how to "onion skinning"?

[Chipp Walters]

Mark,

Unless you average the 3, your gray-scale result may not work
properly. Try it on an image with 3 circles: 100%R, 100%G, 100%B and
you'll see what I mean.

On Nov 28, 2007 9:32 PM, Mark Smith <mark at maseurope.net> wrote:
> This is sort of interesting:
>
> if you simply take one of the color bytes of each pixel, and copy it
> to the other two color bytes, you get a gray-scale result. The
> brightness/contrast varies with which color you choose. For the few
> images I've tried, it seems to be red =brighter/less contrast  to
> blue= darker/more contrast. This may be no surprise to the pro image
> wranglers among us, but seemed intriguing to me.
>
> function MakeGS @indata ---- the imageData of the source image
>     repeat with n = 1 to length(inData) - 3 step 4
>        get char n+3 of inData  ---- blue byte, 1 for red, 2 for green
>        put null & it & it & it after outData
>     end repeat
>     return outData
> end MakeGS
>
> and it runs perhaps twice as fast as taking an average.
>
> Best,
>
> Mark
>
>
>
>
> On 28 Nov 2007, at 23:06, Ian Wood wrote:
>
> >
> > On 28 Nov 2007, at 21:24, Chipp Walters wrote:
> >
> >> Or, you could probably do it really fast with an optimized imagedata
> >> script where you average the values of each pixel and reapply. I
> >> would
> >> think that would zip right along.
> >
> > I managed to find a function from March last year from a discussion
> > about making alphadata from images.
> > Originally written by Wilhelm Sanke, with a few tweaks by me to
> > make it universal for any image size.
> >
> > Pass it the long ID of an image and it will return a one-channel
> > image suitable for a mask.
> >
> > On 13 Mar 2006, at 20:51, Ian Wood wrote:
> >> function makeMask tMaskImg
> >>   set the cursor to watch
> >>   put width of tMaskImg into tW
> >>   put height of tMaskImg into tH
> >>   put the milliseconds into Start
> >>   put the imageData of tMaskImg into iData
> >>   put empty into tmaskdata
> >>   put tW * 4 into re
> >>   repeat with i = 0 to (tH - 1)
> >>     repeat with j = 0 to (tW - 1)
> >>       put  chartonum(char (i*re + (j*4+2)) of idata) into tC1
> >>       put chartonum(char (i*re + (j*4+3)) of idata) into tC2
> >>       put  chartonum(char (i*re + (j*4+4)) of idata) into tC3
> >>       put the round of ((tc1 + tc2 + tc3)/3) into tM
> >>       put numToChar(tM) after tMaskData
> >>     end repeat
> >>   end repeat
> >>   return tMaskData
> >> end makeMask
> >
> > Add another tweak to put it back into RGB:
> >
> > function makeMask tMaskImg
> >   set the cursor to watch
> >   put width of tMaskImg into tW
> >   put height of tMaskImg into tH
> >   put the milliseconds into Start
> >   put the imageData of tMaskImg into iData
> >   put empty into tmaskdata
> >   put tW * 4 into re
> >   repeat with i = 0 to (tH - 1)
> >     repeat with j = 0 to (tW - 1)
> >       put  chartonum(char (i*re + (j*4+2)) of idata) into tC1
> >       put chartonum(char (i*re + (j*4+3)) of idata) into tC2
> >       put  chartonum(char (i*re + (j*4+4)) of idata) into tC3
> >       put the round of ((tc1 + tc2 + tc3)/3) into tM
> >       put numToChar(tM) into tPix
> >       put tPix & tPix & tPix & tPix after tMaskData
> >     end repeat
> >   end repeat
> >   return tMaskData
> > end makeMask
> >
> > And you can do something like:
> >
> > put makeMask(long id of img 1) into tData
> > set the imagedata of img 1 to tData
> >
> > to turn the specified image into greyscale. Takes about a second
> > for a 640x480px image on a MBP 2GHz Core Duo, so not too speedy.
> >
> > Ian
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