Non arcade related assistance required.

[Drnick]

My wife wants some prints that I have blowing up from A4 to something along the lines of A0.  The images have been printed out on a High DPI printer.  (I am unsure of the exact DPI used but the images look good to the naked eye).  My question is what way would be best to enlarge these.  I have scanned them into the computer at various different resolutions.  But when I look at the images I can then see the marks from the printer. These are quite pronounced.   

I also have them as digital images of about 3000 x 2000 @ 72DPI (Which as we know is ok for screen and useless for printing).

The images themselves are very cartoony to start with so I guess I can get away with a bit of blur, but not too much as I don't want to lose all the little details.

Ideally I would like to know how to do it using Gimp as that is what I have to hand, but I can always throw it on a machine at work if I need Adobe products to fix.

Here is a quick sample of what I mean,  It has been scanned at 1200DPI.  and the 72dpi version for comparison.

Would I be better off working with the 72 DPI images?

[thatpurplestuff]

Those example scans are confusing to me since it appears that the higher resolution scan looks worse at the same scale... with a higher resolution scan you SHOULD only be seeing that pattern as you zoom in further into the image, but those appear to both be the same distance which doesn't make any sense.  It's Monday so I may just be confused haha.

Ideally your final print file would be no less than 300 PPI, which would mean for A0 size you're looking at 9930 x 14040 px.  If the images are all similar to what you posted (meaning soft cloud edges with no hard lines), you could enlarge the 72 PPI file to the required size and then hit it with Reduce Noise and Gaussian Blur filters until you're happy with the result... it won't be exact but it will be pretty close.  If the images contain fine details, you're really kinda stuck since you're going to be working from scans that contain the print patterns from the source printer.  You can try to remove the scan patterns using the Noise/Median filter, but I've had mixed results with that technique.

[Slippyblade]

That's a moire pattern.  I've seen it happen when oversampling textures for graphic work but not sure how it happened with those pics. 

[Drnick]

Thanks for the info.  I think I'm just going to go with the 72DPI's and blow them up and use some filters.  I, don't think I'll be able to do anything with the prints I have as regardless of scanner I get the same results as soon as I scan higher then 600DPI.

I'm going to have a go with blowing up the 600DPI scans first though.