Problem with mask
sanke at hrz.uni-kassel.de
Tue Oct 21 17:38:57 EDT 2008
In the meantime Jim has sent me the essential script offlist from which
I recreated a test stack.
He wrote (to this list):
> Well, my problem with mask is no more.
> Turns out the Run Rev within() function is a bit strange.
> The masked ellipse is flat on the right side and the bottom because
> within() counts the left and top of a graphic to within the graphic,
> but not the right and bottom.
Well, among the variations I tried with your script there is one where I
reversed the direction of "scanning" the graphic.
"put the topLeft of img 1 into tTopLeft
put item 1 of tTopLeft into x0
put item 2 of tTopLeft into y0
# repeat with j = 1 to tHeight
# repeat with i = 1 to tWidth
#now. reversed direction
repeat with j = tHeight down to 1
repeat with i = tWidth down to 1
put x0+i,y0+j into tPt
if within(grc 1, tPt) then
put tClear after tData
put tBlock after tData
The result of this change of direction is that now the flat edges appear
on the left and on top, meaning we still need to define a "within" bug
more accurately, but I don't know how.
Increasing the rect of the image so that it extends to outside the rect
of the graphic does not make any difference.
In the case of Photo Patchworks such a strategy worked with a "padded"
corresponding template image whose transparency mask was then used for
the cropped image of the same size.
Only the "edges" I got from a non-padded mask image are different from
Jim's: I get black lines by the side and not flattened edges.
Joe Lewis Wilkins pepetoo at cox.net wrote:
> Hi James,
> In one of this threads first responses, I implied as much when I said
> that you probably needed to subtract one from all right and bottom
> coordinates, since this has been a problem for a very long time. Of
> course, I don't know if just a minus one would have cured everything,
> but it may have helped.
if what you mean is a change in the script like here
repeat with j = 1 to tHeight -1
repeat with i = 1 to tWidth -1
then you get a distorted mask because the mask data to not fit exactly
into the rect of the image.
I am still puzzled by this bug.
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