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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