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notcurses_visual.3: fully detail octant blitter

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nick black 2024-12-25 03:12:26 -05:00
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doc/man/man3/notcurses_visual.3.md
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@ -254,19 +254,20 @@ to work out very well for images, but (depending on the font) can be very
good for plots.
A string can be transformed to a blitter with **notcurses_lex_blitter**,
recognizing **ascii**, **half**, **quad**, **sex**, **fourstep**, **braille**,
**eightstep**, and **pixel**. Conversion in the opposite direction is performed
with **notcurses_str_blitter**.
recognizing **ascii**, **half**, **quad**, **sex**, **oct**, **fourstep**,
**braille**, **eightstep**, and **pixel**. Conversion in the opposite direction
is performed with **notcurses_str_blitter**.
In the absence of scaling, for a given set of pixels, more rows and columns in
the blitter will result in a smaller output image. An image rendered with
**NCBLIT_1x1** will be twice as tall as the same image rendered with
**NCBLIT_2x1**, which will be twice as wide as the same image rendered with
**NCBLIT_2x2**. The same image rendered with **NCBLIT_3x2** will be one-third
as tall and one-half as wide as the original **NCBLIT_1x1** render (again, this
depends on **NCSCALE_NONE**). If the output size is held constant (using for
instance **NCSCALE_SCALE_HIRES** and a large image), more rows and columns will
result in more effective resolution.
**NCBLIT_2x2**, and double the height and width of the same image rendered
with **NCBLIT_4x2**. The same image rendered with **NCBLIT_3x2** will be
one-third as tall and one-half as wide as the original **NCBLIT_1x1** render
(again, this depends on **NCSCALE_NONE**). If the output size is held constant
(using for instance **NCSCALE_SCALE_HIRES** and a large image), more rows and
columns will result in more effective resolution.
A string can be transformed to a scaling mode with **notcurses_lex_scalemode**,
recognizing **stretch**, **scalehi**, **hires**, **scale**, and **none**.
@ -276,7 +277,9 @@ Assuming a cell is twice as tall as it is wide, **NCBLIT_1x1** (and indeed
any NxN blitter) will stretch an image by a factor of 2 in the vertical
dimension. **NCBLIT_2x1** will not distort the image whatsoever, as it maps a
vector two pixels high and one pixel wide to a single cell. **NCBLIT_3x2** will
stretch an image by a factor of 1.5.
stretch an image by a factor of 1.5. **NCBLIT_4x2** will preserve the aspect
ratio similarly to **NCBLIT_2x1**, but can lose color fidelity (there can be
more than two colors in a block of eight pixels).
The cell's dimension in pixels is ideally evenly divisible by the blitter
geometry. If **NCBLIT_3x2** is used together with a cell 8 pixels wide and
@ -346,11 +349,10 @@ or if both ***nc*** and ***n*** are **NULL**.
**ncvisual_media_defblitter** returns the blitter selected by **NCBLIT_DEFAULT**
in the specified configuration. If UTF8 is not enabled, this will always be
**NCBLIT_1x1**. If ***scale*** is **NCSCALE_NONE** or **NCSCALE_SCALE**, the
aspect-preserving **NCBLIT_2x1** will be returned. If octants are
available (see **notcurses_canoctant**), this will be **NCBLIT_4x2**,
or otherwise, if sextants are available (see
**notcurses_cansextant**), this will be **NCBLIT_3x2**, or otherwise
**NCBLIT_2x2**.
aspect-preserving **NCBLIT_2x1** will be returned. For **NCSCALE_STRETCH**,
**NCBLIT_4x2** is chosen if octants are available (see **notcurses_canoctant**),
otherwise **NCBLIT_3x2** if sextants are available (see **notcurses_cansextant**),
and otherwise **NCBLIT_2x2**.
# NOTES
@ -363,11 +365,10 @@ a multimedia backend include **ncvisual_from_file** and
Sixel documentation can be found at [Dankwiki](https://nick-black.com/dankwiki/index.php?title=Sixel).
Kitty's graphics protocol is specified in [its documentation](https://sw.kovidgoyal.net/kitty/graphics-protocol.html).
Bad font support can ruin **NCBLIT_2x2**, **NCBLIT_4x2**, **NCBLIT_3x2**,
**NCBLIT_4x1**,
**NCBLIT_BRAILLE**, and **NCBLIT_8x1**. Braille glyphs ought ideally draw only
the raised dots, rather than drawing all eight dots with two different styles.
It's often best for the emulator to draw these glyphs itself.
Bad font support can ruin **NCBLIT_2x2**, **NCBLIT_3x2**, **NCBLIT_4x1**,
**NCBLIT_4x2**, **NCBLIT_BRAILLE**, and **NCBLIT_8x1**. Braille glyphs ought
ideally draw only the raised dots, rather than drawing all eight dots with two
different styles. It's often best for the emulator to draw these glyphs itself.
Several emulators claim to implement Sixel, but do so in a more or less broken
fashion. I consider **XTerm** and **foot** to be reference Sixel