Need a filter that performs a find/replace function on certain pixels

Hey, folks. I've got what seems like a simple request. Whether it's as simple to execute as it is to describe... well, we'll see.

What I'm looking for specifically is a filter that analyzes the pixels in an image consisting only of black and white (no gray!) pixels and replaces white pixels bordered by eight black pixels.

In other words, let's consider three 3x3 pixel blocks, where "X" = a black pixel (RGB 0,0,0) and "O" = white pixel (RGB 255, 255, 255):

XXX OXX XXX
XOX XOX XXO
XXX OXX OOX

The filter I need would seek out the white pixels (0) with no adjacent white pixels and replace those solitary white pixels with black (X). So the result of applying this filter to those blocks above would result in:

XXX OXX XXX
XXX XOX XXO
XXX OXX OOX

The white pixel in the first block is turned black because it has no white neighbors. However, the white pixels in the second and third blocks remain unchanged. Make sense?

Okay... so. How to do this?


Thanks for your time.

-- McJ

Once we get the bitmap-based Script component it'll be as simple as a single for loop. (Probably)
I'm not up on LUA at the moment because all the effects I'd want to write are bitmap-based, otherwise I'd give you at least pseudo-code...

Here's my attempt at it. It's clunky an inelegant, but it sort of works. I say sort of b/c it gets most of the image right, but there are a few areas where it will mis-identify an area surrounded by 7 as being surrounded by all 8.

A neat side-discovery is at the bottom: a way to identify horizontal and vertical lines.

Pixel Comparison.ffxml

Oh, my! Sphinx, this rocks so hard! Just what I needed!

And Corvus, much thanks for your work, but I don't really understand how to use it. Any pointers?

-- McJ

Ah. Well, thanks anyhow. Appreciate the effort!

@Sphinx: I think he is making a FF based "Game of Life"

Now we rescale it to at least 1.5x and we get:

Those blobs out lined in red are the offspring of some of those solitary pixels I needed killed. These solitary blobs are made up of the exact same configuration of grayscale pixels. Whether the blobs are white blobs on a black background, or black blobs on a white background, their repetition disrupts the wonderful irregularities that are created by a thriving ecosystem of pixels. THEY MUST BE DESTROYED!!!

So let's return to that fist image. We apply Sphinx's filter once, invert the image, apply the filter again, invert and we get:

Much better!

Now, I'm seeing that there are certain configurations of pixels that resist the transition to filigree. Here's a zoomed-in view of the culprits.

Sphinx, you might just number all the 8 adjacent pixels and wire them into on/off controls - that would make it generalized and less specific. Like so:

8 1 2
7 X 3
6 5 4

Then it could be a generic pixel adjacency seek and destroy component
You could do all sorts of stuff with that: seek and destroy horizontal or diagonal lines for example.

Borkus: have you used Perfectum, by Redfield? I also does some neat effects, similar to the alien skin filter. Works great for smoothing out JPEG badness.

Quote
CorvusCroax wrote: Borkus: have you used Perfectum, by Redfield?

Yes, I really like Perfectum. But its results are generally wispy -- and what I'm doing with Blow Up is more... chunky?