http://img811.imageshack.us/img811/2623/vhd.png
It is a scientific approach based on the prior decade of research in computer graphics journals; called "Super Resolution from single, library or moving images" (depending on the paper). Here is a website showing one researchers comparison pics using one approach ...http://www.wisdom.weizmann.ac.il/~vision/SingleImageSR.html ...as you can see this method is intended for fairly detailed photos and not blurry grainy VGA textures...
This implementation is my own that has taken several months of coding to get something that works for textures, there is little art involved as it mostly just science. Having played vanilla MW on my ancient laptop at VGA rez over the holidays without my 4GB retexture collection, I was motivated to get back to vanilla but it looked very blurry on my living room large screen HDTV, thus I intend to finish this before I roll another character!
What I do is start with the .tga texture from the Construction set CD to avoid starting with the already compressed .dds. Then as shown in the vhd.png - the first step is to upsize it twice over with an interpolation filter to get a hirez version that is blurry. The next step is the crucial piece of the algorithm that took a long time to get right, the premise is that if it "learns" what details are lost in downsizing training images, then it can "restore" similar upsizing details in new images. Finally I use Gimp to convert to a new .dds that is possibly 16x larger depending on compression efficiency, but that seems about right comparing 2002-2012 advancement in video cards. In GIMP DDS converter I use Lancsoz mipmaps with 2.2 gamma dithered, and DXT1 unless edge alpha then DXT3
For the moss example I spent a long time sifting google images for closeup pics of spanish hanging moss without camera grain or jpeg compression that are of similar scale to the upsized texture. If the thumbnail view of the texture looks identical to vanilla, the algorithm is functioning as it is constrained to only adding details that do not change the lo-rez versions of the image. BTW I recommend highly windows thumbnail viewers for .DDS/.TGA as it makes it so much easier to decide on making texture swaps.
Just to give you an idea of the run-time order - I do sixteen passes over all million pixels in a 1kx1k texture (upsized from a 256x256) looking thru possibly 1-2 dozen training images each of a million pixels - for an order of 1Mx1Mx16x16...since I don't have the latest greatest CPU with the latest greatest GPU best to start small with the 64x64 flora textures before I tackle cloud and moon textures! My priorities are flora to get my alchemists happy, wood to keep the starting character happy with the shacks and basically work my way around the map, hitting roads and regions as I go. At some point I need to do parallel processing on the physics based GPUs or I will never finish. I may just skip amulet_extravagant in the final library as for the last few months that has been my truth image trying to get a 16x16 downsize/upsize back to the original 64x64 texture!
l have more work to do on the alpha channel - as this was the first one I tried that was more than just an edge alpha. But don't get too excited about a short term release - as it takes hours to google quality training images, hours to classify them into the training database, and hours to search the training database finding lo/hi-rez patch pairs that can be used to enhance the target texture. Just to do kreshweed, black_anther, wickwheat, willow_flower, saltrice, marshmerrow, black_anther, and the bc_moss you see here took two weekends. Running on an older Athlon XP64x2 with 2GB memory, but trying to do two at once locks up my machine. So googling more training images to get ready for the next texture while the prior one is processing. And hopefully I only stay long enough in the game to verify the textures are working and realize the rest of the vanilla textures need finished!
Update Status mixed in the Scenic and Alchemy Flora since they overlap in parts
DONE
ashtree
bc_fern
bc_fungus
bc_moss
bc_mushroom (needs Flora Glow enhancement)
bittergreen
black_anther
emperor_parasol
lichens
hackle-lo
kreshweed
marshmerrow
muckpod/sponge (needs Graphic Herbalism enhancement)
tx_mushroom
saltrice
scathecraw
wickwheat
willow_flower
IN PROGRESS
bc_bark
bark
fire_fern
comberry
stoneflower
TODO
ash_yam
caveplant
chokeweed
cork_bulb
bc_podplant (Needs Flora Glow enhancement)
roobrush
tramaroot
ash_grass
bc_grassblade
bc_leaves
bc_lilypad
branches
grass_blade
ivy
kelp
treering_wg
vine