🚀 go-pugleaf

In article <1992Nov1.212253.16619@gandalf.UMCS.Maine.EDU> fishboy@gandalf.UMCS.Maine.EDU (Jon Everett) writes:
>
>Question:
>
>Can anyone provide a decent explanation of how
>the 'spot function' works in halftoning?  From what I have
>read in the Adobe Books, the function is supposed to take
>x,y coordinates of a pixel in the halftone cellbox as arguments.
>To me this is counter-intuitive. I would expect it to take a
>gray value as input and return the bitmap of the cellbox.
>Can anyone provide, or point me to, a fuller explanation of 
>the spot function's operation and its palce in the larger 
>context of halftoning?  I would like to be able to explicitly
>define the order in which the pixels in a cellbox of a given
>size are turned on.

You can have your wish.  Read pg. 85-86 of the old red book again.   Your spot
function describes how the spots in each cell should be turned on.  For each
x,y coordinate within the cell the spot function returns a value between -1.0 
and 1.0 which the screening engine uses to determine your desired order of
blackening (or whitening depending on how you look at it).  There's 
more detail in the green book, but you can look that up yourself. :)














				Rob
-- 
Rob Bradlee  w:(508)-658-5600 X5153 
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