Search found 8 matches

by Piotr Grochowski
2019-08-31T11:38:02-07:00
Forum: Users
Topic: Don't use linear light when enlarging with Lanczos et al
Replies: 27
Views: 35695

Re: Don't use linear light when enlarging with Lanczos et al

Hmm, well, I would say you have shown that the artifacts introduced by rasterizing text too small, then upscaling it, are nasty. Those artifacts are there in the "<font face='DMCA Sans Serif' style="font-size: 15px">incorrect upscaling</font>" column because it really is incorrect. The rasterizatio...
by Piotr Grochowski
2019-08-31T09:37:52-07:00
Forum: Users
Topic: Don't use linear light when enlarging with Lanczos et al
Replies: 27
Views: 35695

Re: Don't use linear light when enlarging with Lanczos et al

The point is, anything else than linear RGB is technically incorrect because it introduces artifacts that don't make sense.

Image

The artifacts introduced by the misuse of sRGB values are nasty.
by Piotr Grochowski
2019-08-31T05:59:52-07:00
Forum: Digital Image Processing
Topic: Cosine-sum filters for resampling
Replies: 7
Views: 3243

Re: Cosine-sum filters for resampling

It would be interesting to research and find out if cosine-sum filters (whether "tensor" or "EWA") are any better than windowed Sinc filters and cubic filters.
by Piotr Grochowski
2019-08-30T23:08:07-07:00
Forum: Digital Image Processing
Topic: Cosine-sum filters for resampling
Replies: 7
Views: 3243

Re: Cosine-sum filters for resampling

Yes, but can you point to some reference so that we can see what is being done or is this just some idea of yours with no current background or theory? This page demonstrates various window functions of the cosine-sum structure: https://en.wikipedia.org/wiki/Window_function#Cosine-sum_windows As fo...
by Piotr Grochowski
2019-08-30T21:13:06-07:00
Forum: Digital Image Processing
Topic: Cosine-sum filters for resampling
Replies: 7
Views: 3243

Re: Cosine-sum filters for resampling

IM has "-filter Cosine" for resampling. I don't know if this is the same as the OP. "-filter Cosine" is using a Cosine window (made with a cosine function) to window the Sinc function to produce the filter. Cosine-sum filters are made by adding cosine functions to produce the filter. Those are not ...
by Piotr Grochowski
2019-08-30T00:50:31-07:00
Forum: Digital Image Processing
Topic: Cosine-sum filters for resampling
Replies: 7
Views: 3243

Cosine-sum filters for resampling

Cosine-sum filters for resampling are filters that are designed as a sum of cosine functions, which is then truncated to a desired width. An example formula for width-4 (range from -2 to 2) cosine-sum filters would be: a+b×cos(90°×input)+c×cos(180°×input)+d×cos(270°×input)+e×cos(450°×input)+f×cos(54...
by Piotr Grochowski
2019-08-28T08:18:58-07:00
Forum: Users
Topic: Don't use linear light when enlarging with Lanczos et al
Replies: 27
Views: 35695

Re: Don't use linear light when enlarging with Lanczos et al

This seems to be some sort of a paradox. On one hand, using anything but linear RGB (or some obscure transform of it that gives equivalent results, I don't know if XYZ is one) is mathematically incorrect and distorts the general brightness/color of the picture just like wrong colorspace downscaling ...
by Piotr Grochowski
2019-08-27T21:32:16-07:00
Forum: Kudos and Rants
Topic: what is happening to my account
Replies: 1
Views: 5455

what is happening to my account

I got a login error "You have specified an incorrect username. Please check your username and try again. If you continue to have problems please contact the Board Administrator." indicating that the account was deleted, but this happened twice so far! What is happening?