Re: need some help with custom filter in Photoshop

From: Tim Auton (tim.auton_at_uton.groupSexWithoutTheY)
Date: 02/27/05 

Date: Sun, 27 Feb 2005 23:28:00 +0000

"Blaine Waddington" <v@z.m> wrote:
>
>Boy, this seems to be some tough math here but I think I'm beginning to
>understand it. Let me try to phrase what I think is happening:
>
>If I have a 7x7 kernal, for example, and apply that to a 500x500 pixel
>image, each pixel will be changed according to the configuration of the 7x7,
>or would this be each 7x7 pixel area being changed?

The former. Each pixel is based to the values of the pixels in the 7x7
area centred on that pixel. The result for that pixel is the weighted
sum of the 49 pixels, (the weights being those of the kernel). You do
this for every pixel individually.

>I inputted the values for vertical lines and such, as well as tried selected
>blurs in only certain directions. I think I'm beginning to understand the
>process. Let me try to understand a bit more with the following question:
>
>Suppose I have a tiny 5x5 pixel image for 25 square pixels. I apply a 7x7
>matrix. Is this matrix too large for this tiny image? Should my image have
>been at least a 7x7 size as well?

Edge effects are a bit more complex no matter the size of the image.
In the 7x7 case, there simply aren't 3 columns of pixels to the left
of the leftmost column of pixels. I just crop the edges.

Tim 

-- 
This is not my helicopter.