Created on 19.02.2005 - 11:45

This is allready an (ARB) implementation.

More like:

In grayscale it is about all color components have the same value.

One of the possible transformations to grayscale is for example:
float tmp = (color.r + color.g + color.b)/3.0;
color.rgb = vec3(tmp, tmp, tmp);
...
or:

blur is (convolution explanation):

1 1 1
1 5 1
1 1 1

sharpen:

-1 -1 -1
-1 10 -1
-1 -1 -1

It is more easy to write a shader in a custom HLSL after such a general problem description.

Otherwise the writer has to find it out for himself and if has bought himself two nice PSX games he didn't play yet it can take come time...