Commit Graph

8 Commits

Author SHA1 Message Date
kris
bf76271d75 NTSC conversion should be using YIQ space instead of YUV, which seems
to explain several fudge factors I needed to include to match colours.
2021-11-02 23:28:58 +00:00
kris
4fbb0faf84 Fixes 2021-11-02 15:47:37 +00:00
kris
b63fd81c07 Unify DHGRScreen implementations 2021-11-02 15:23:23 +00:00
kris
d442baf1f1 Tidy a bit 2021-11-02 12:30:43 +00:00
kris
e08f25e4cc Simplify 2021-07-19 12:55:50 +01:00
kris
467a0cd196 Tidy up a bit to prepare for merge 2021-03-15 10:45:33 +00:00
kris
e0b732cdaa Reimplement NTSC conversion to closely match openemulator output. I
can't figure out why contrast=2 is needed (openemulator uses a default
value of 1, so there must be a factor of 2x somewhere), or where the
slight hue rotation comes from - perhaps this is somehow introduced by
the more complex band-pass filtering that openemulator does?

I needed to also account for the DHGR timing difference that
introduces a phase offset of 1 pixel between the memory values and
displayed pixel timings.

Fix a last-minute bug with palette precomputation.
2021-02-17 21:29:43 +00:00
kris
ad9515dcf2 Implement NTSC emulation, using an 8 pixel window for chroma signal.
Use this to precompute a new ntsc palette with 256 entries (though
only 84 unique colours) that are available by appropriate pixel
sequences.  Unfortunately the precomputed distance matrix for this
palette is 4GB!

Optimize the precomputation to be less memory hungry, while also
making efficient use of the mmapped output file.

Add support for dithering images using this 8-bit palette depth,
i.e. to optimize for NTSC rendering.  This often gives better image
quality since more colours are available, especially when modulating
areas of similar colour.

Fix 140 pixel dithering and render the output including NTSC fringing
instead of the unrealistic 140px output that doesn't include it.

Add support for rendering output image using any target palette, which
is useful e.g. for comparing how an 8-pixel NTSC rendered image will
be displayed on an emulator using 4-pixel ntsc emulation (there is
usually some colour bias, because the 8 pixel chroma blending tends to
average away colours).

Switch the output binary format to write AUX memory first, which
matches the image format of other utilities.
2021-02-14 23:34:25 +00:00