Any suggestions on how to "onion skinning"?

[Mark Smith]

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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