Know a easy way to create seamless isometric tile?

Anybody know an easy way to create seamless isometric tiles from existing (seamless) textures?
A ready-to-use-tool would be ideal.
At the moment I take a seamless texture, copy and paste in in a 4-tiled square, rotate it 45 degrees in paintshop, copy an past the middle in a new image, make this seamless and rotate it 45 degrees back.
(oh yeh,I also stretch it in height)
There must be a simpler way to do this, though I can't find it.

Tilestudio maybe.

http://www.gamedev.net/community/forums/topic.asp?topic_id=381711

Open the texture in Photoshop (or any similiar)
Rotate canvas by 45 degrees
Scale the Y to 1/2 (if it's 64 make it 32)

ehm;
That would leave me with a 45 degrees turned texture and still not seamless.
In Photoshop I could:
1: open a larger texture
2: rotate it 45 degrees
3: copy and paste the center into a new texture
4: rotate this 45 degrees back.
Presto: an isometric texture in witch up is up and down is down.
But it's not seamless! Plus the width and hight are wrong.

I've googled for "seamless isometric": there is very little source to be found.
atm I'm trying to convert some of Jesse's code for rotating pixmaps to something I can unleash seamless tiling algorithms on.

mortiis is right thats how you make seamless iso textures,

I was wrong there:sorry... Just forgot the original texture was already seamless. --blush--
But:


Yes, it's seamless(forget about the green line(just there to show direction)),
but it's tilted.
(if the texture were to represent long grass, I don't want it to look as if a storm swept it to the ground) so I want the black lines to stay horizontal and vertical.
Not as easy as it may look on first glance,is it...

So you practically want to cut the edges in a 45° angle(texture has to be 4-tiled of course)?
A simple BB-routine should work here too.

Oh, brother...
Well, that is more or less what I'm doing now, since there is NO SIMPLE SOLUTION.
I'm indeed (in BB)cutting the edges, rotating the remainder in a tile of the same size as the original, unleash seamless algorithm and turn it back to its original position.
And I'm glad it finally works, for I had to rely heavily on code from Jesse and Yan, of witch I did not understand half.