That tool you have...is that similar to high pass? I've used high pass on textures before to even the brightness, but it kills off the colors.
The program I use is a spatial filter which does Fourier analysis. If either of those things mean much then ill talk about it and share filters as it can be indispensable but otherwise its a hard technique to use.
I am using a high pass filter but I am keeping the average or DC component. The program allows you to set how much of the high pass to keep. I am only knocking out a little of the low pass - just enough to even out the brightness.
In theory if you use a high pass and a very very large blur - enough to average the whole image to a single shade and then add the two together then it should produce the same effect. Generally tho, most paint packages clip the high pass or center it around the mid grey mark so that when you add them it would not look right.
I had posted more detailed steps on the manual method previously here:
Originally Posted by Redrobes
FFT and IFT. Two photoshop filters I can't get for mac. On my budget anyway. I've been interested in direct frequency synthesis for some time, but I can't seem to find the tools.
GeoTerSys is really starting to sound like an, "everything-plus-one-kitchen-sink," tool. Good luck building it, mate.
I didnt realize that photoshop could do FFT's. I tried looking for a freebie image processor which includes an FFT/DFT transformer but I had no luck. I did come across this which has a lot of write up about what they are all about.
Originally Posted by su_liam
Fascinating is that half way down it talks about doing high pass filters and keeping the DC component and then not two images underneath is a section about tiling images with a texture not that dissimilar from the tutorial above. Obviously its not just me that does this then.
A spatial filter can do some really magic stuff that would seem impossible. For example it can remove a grid from images pretty efficiently without altering the original. This is showing a bit of Publius December challenge where the hatching has been removed. It does destroy a bit of the normal image but its not that bad becuase the filter is so strongly targetted.
My little app is not part of Geo. Its very old actually but its another of those hard to use - well hard to explain how to use apps that gathers no interest outside of a specialist world.
Rob, I checked out this post as follows...
Originally Posted by RobA
What you are doing here is generating the low pass version and removing that from the image leaving the high pass only which would even out the brightness. Its that step of desaturating thats a bit odd. What I reckon you need for this technique is to take an image and call it A. Clone it to B and again to C. Take C and blur it so massively that its one uniform shade. Take B and remove C from it - thats sort of like the ultimate desaturation. Take that result and blur it a little and then remove this image from A. Then you would be removing the low frequencies but not the DC component so it should give the high pass but keep the DC colour. Its the same as doing the high pass and adding back in the DC of course as its A - (B - C) which is A - B + C. I'm still not sure how you can actually achieve this without the colour values going negative which would be clamped and then it wont work correctly. The only way I can see of getting around this is to split the images up into parts lighter than DC and parts darker than DC and process separately. I'll try this out offline and see if I can get that to work.
Originally Posted by RobA
I tried this technique and its fine so here are the steps. Its a lot like RobA's but it wont have the desaturation stage and its probably more predictable because of it.
Get an image 1.
Blur it quite a lot 2.
Blur it until its a constant colour 3.
Use Image arithmetic to generate 2 - 3 => 4
Use Image arithmetic to generate 3 - 2 => 5
Take 1 and subtract 4 and add 5 => 6
...which is the equivalent to the spatial filtered image for high pass but with DC left in. You can do these stages to the tiled image if required.
Back in the Dark Ages I had the google-fu and infinite wells of patience to research ift and fft filters for photoshop. I found at least one commercial filter and I could swear I found a free filter for Windoze. I also downloaded an open source frequency synthesis image app. Unfortunately, the source was included in a self-opening archive, an exe. At that point, after wading through pages and pages of irrelevant(although sometimes interesting) entries, I gave up and washed my hands of it. Apparently FFT and IFT are very common in sound editing apps...
I'm wondering if the desat he's using isn't to retain a bit more of the color information. Like retaining the DC component in the high pass rather than adding 128-grey. I'll have to mess with that meself.
IIR the desaturation was due to combining that layer using an overlay blend...it seemed to give the results I was looking for...Now I need to go back and play with yours (which makes the most sense having read that reference you provided on FFT and image processing.) I'd rep you for the reference, but I can't :(
I reckon that the desat is having a similar effect as keeping some of the DC component. By removing the blur (merging the negative of it) the desat stage is to not take as much of that DC away as if you would if you didn't do it. If you didn't then the image would drop to near black.
Anyway, I am a big fan of ImageMagick (.org) and so I was thinking of a) getting some scripts together to do the tiling and the flattening of the images into tiles and then b) convert script into cgi and make a web page out of it so that you can upload an image and then push a button to get its tiled equiv. That would be well handy for everyone not least me.
Anyone know if this web host run Perl based CGI ?