The example sent by
email@hidden does scale a 2749 x 5399 picture
to 500 x 981.
After giving this some more thought, this is, I think, a better solution.
When working with graphics it's always better to scale down. If you scale up, you're adding information, and the first solution I posted was scaling up on images that didn't round to a width of 500 pixels.
The challenge, of course, is to make sure the height is multiplied (or divided) by the same amount as the width in scaling the image. Since we know what the new width dimension will be, we can get the aspect ratio (w/h) of the image, and use that to determine the new height.
I also broke the scaling commands into a handler, which is how I'd implement this. You may notice a difference of one pixel from the scaling GC does. That's because the GC rounding method is different from AppleScript's.
HTH,
ES
tell application "GraphicConverter"
activate
open theFile
set image dimension of window 1 to {3264, 2448}
set {picWidth, picHeight} to my ScaleImage()
display dialog "Width= " & picWidth & " Height= " & picHeight
-- save window 1 in (destFldr & theName & "_500")
--close window 1 saving no
end tell
on ScaleImage()
tell application "GraphicConverter"
set {picWidth, picHeight} to image dimension of window 1
set image dimension of window 1 to {500, round (500 / (picWidth / picHeight))}
return image dimension of window 1
end tell
end ScaleImage