Well, one alternative that also seems to work is to map the 24bit
value of each pixel to an 8bit value :
function makeGS @inData
repeat with n = 1 to length(inData) - 3 step 4
get binarydecode("M", char n to n+3 of inData, tPix)
put numtochar(tPix div 65536) into tv
put null & tv & tv & tv after outData
end repeat
return outData
end makeGS
It's maybe 25% quicker than dealing with each color component
individually.
Best,
Mark
On 29 Nov 2007, at 09:48, Wilhelm Sanke wrote:
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.
And Chipp Walters chipp at chipp.com wrote:
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.
My experience is that with most photos you get a very nice
grayscale image using the red pixel and copying the value to the
other two pixels like Mark suggested.
The last public version of my "Imagedata Toolkit Preview 3" (update
of April 17)
<http://www.sanke.org/Software/ImageDataToolkitPreview3.zip>
contains both grayscale routines using "average" and those with
copying one color pixel to the other two - implemented for all
three colors.
Speed for "average gray" and a 640X480 image (on a 2 GHz machine)
is about 1.1 seconds and for "gray from red" about 600 milliseconds.-
The next update of the Imagedata Toolkit, which will be the last
with a restriction to an enforced image size of 640X480, will
probably be released before Xmas and contain a number of major
enhancements (among them: scripted Rev emulation of cubic
enlargement, integration and expanding of some new Gluas filters
from Gimp - translated into Revolution - "stretch contrast",
"compress contrast", enhancement of "jitter" filters with various
multi-pixel jitters, another despeckle filter based on minimum
differences between surrounding pixel pairs [this is another Gimp/
Gluas development that is identical in effectiveness to the
"median" approach, but somewhat slower], exchanging color values
within a defined range by clicking on image and/or color scale,
copying - and enlarging or shrinking - and pasting oval or
rectangular portions of an image into the same or another image
with variable fringe and/or overall blending into the basic image).
Best regards,
Wilhelm Sanke
<http://www.sanke.org/MetaMedia>
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