RE: Can someone help me with these FF commands ?

["MacBeth, Bill" <bill.macbeth@compaq.com>]

Thomas,
First off, the cnv command doesn't work properly on PCs (don't know about
Macs) for large images in Filter Factory (images more than about 300 x 300).

In situations when it does work, here's an explanation of what it does with
the pixel values.  Consider the pixel "5" and its adjacent pixels 1-4 and
6-9 as shown below.
    1 2 3
    4 5 6
    7 8 9

Then cnv(M1,M2,M3,M4,M5,M6,M7,M8,M9,D) evaluates to
 
(M1*pix1+M2*pix2+M3*pix3+M4*pix4+M5*pix5+M6*pix6+M7*pix7+m8*pix8+M9*pix9)/D.

Here are two simple "classic" filters that can be made by putting the
expression into each of the R,G,and B formula fields:
            Blur an image:  cnv(0,1,0,1,4,1,0,1,0,8)   
      Sharpen an image:  cnv(0,-1,0,-1,8,-1,0,-1,0,4)

Note in the above, that the D value is the sum of all the M values.  That is
often the case, but can be changed for special effects.

For a more versatile program than Filter Factory, with a somewhat different
implementation of cnv that works, there is a very comprehensive program
called FilterFormula available at  http://members.aon.at/ats-graphics/

Regards, Bill
   




> -----Original Message-----
> From:	Thomas De Groote [SMTP:Thomas.degroote@rug.ac.be]
> Sent:	Thursday, January 14, 1999 6:47 AM
> To:	ff@aurdev.com
> Subject:	Can someone help me with these FF commands ?
> 
> Hello,
> 
> Is there anyone who can help me with the cnv command ? What exactly does
> it
> do ? In the programming manual there is something about weights, but I
> really can't follow. Can anyone just say in plain English what it does ?
> e.g. It takes the Red value of pixel x,y and so on ?
> 
> Thanks in advance !
> 
> 
> Thomas
> 
> 
> PS : The Macintosh Decompiler is growing ! It now handles FFL, PC compiled
> filters and Mac compiled filters ! Want it ? Mail me and I will arrange a
> web page for it !
>