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Rebased on current master without conflicts and completed the cleanup: comments above new function in longer functions, metadata comments, aligned declarations and simpler guards, consistent braces and shorter lines.

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This commit is contained in:
Michael Grant
2026-10-09 23:37:40 +02:00
parent 6826d87bdb
commit 729b7e7a13
14 changed files with 535 additions and 483 deletions
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69
image-fallback.c
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@@ -48,9 +48,10 @@ struct image_rgb {
u_char b;
};
/* Shading levels cached for the lifetime of an image. */
struct image_glyph_data {
u_char *shade5;
u_char *shade8;
u_char *shade5; /* Cached levels for five-shade output. */
u_char *shade8; /* Cached levels for eight-shade output. */
};
static const struct image_rgb image_ansi_colours[16] = {
@@ -64,6 +65,7 @@ static const struct image_rgb image_ansi_colours[16] = {
{ 0x00, 0xff, 0xff }, { 0xff, 0xff, 0xff }
};
/* Return the squared RGB distance between two colours. */
static u_int
image_glyph_distance(struct image_rgb a, struct image_rgb b)
{
@@ -72,6 +74,7 @@ image_glyph_distance(struct image_rgb a, struct image_rgb b)
return (r * r + g * g + bl * bl);
}
/* Return whether a colour is close enough to grey to use neutral colours. */
static int
image_glyph_low_saturation(struct image_rgb colour)
{
@@ -89,6 +92,7 @@ image_glyph_low_saturation(struct image_rgb colour)
return (maximum == 0 || (maximum - minimum) * 4 <= maximum);
}
/* Find the closest ANSI colour, keeping greys on the neutral ramp. */
static u_int
image_glyph_nearest_ansi(struct image_rgb colour, u_int colours)
{
@@ -97,8 +101,9 @@ image_glyph_nearest_ansi(struct image_rgb colour, u_int colours)
for (i = 0; i < colours; i++) {
if (neutral && i != 0 && i != 7 &&
(colours != 16 || (i != 8 && i != 15)))
(colours != 16 || (i != 8 && i != 15))) {
continue;
}
distance = image_glyph_distance(colour, image_ansi_colours[i]);
if (distance < best_distance) {
best_distance = distance;
@@ -108,13 +113,14 @@ image_glyph_nearest_ansi(struct image_rgb colour, u_int colours)
return (best);
}
/* Map an RGB colour to the terminal palette and its output colour code. */
static struct image_rgb
image_glyph_quantize(struct image_rgb colour, enum image_glyph_palette palette,
int *output)
{
struct image_rgb result;
struct image_rgb result;
int value;
u_int index;
u_int index, ncolours;
if (palette == IMAGE_GLYPH_PALETTE_RGB) {
*output = colour_join_rgb(colour.r, colour.g, colour.b);
@@ -126,8 +132,10 @@ image_glyph_quantize(struct image_rgb colour, enum image_glyph_palette palette,
colour_split_rgb(value, &result.r, &result.g, &result.b);
return (result);
}
index = image_glyph_nearest_ansi(colour,
palette == IMAGE_GLYPH_PALETTE_8 ? 8 : 16);
ncolours = 16;
if (palette == IMAGE_GLYPH_PALETTE_8)
ncolours = 8;
index = image_glyph_nearest_ansi(colour, ncolours);
result = image_ansi_colours[index];
if (index < 8)
*output = index;
@@ -136,6 +144,7 @@ image_glyph_quantize(struct image_rgb colour, enum image_glyph_palette palette,
return (result);
}
/* Fit two colours to a block glyph's pixel samples. */
static void
image_glyph_fit_colours(const struct image_rgb *samples, u_int count,
struct image_rgb centres[2])
@@ -143,6 +152,7 @@ image_glyph_fit_colours(const struct image_rgb *samples, u_int count,
u_int sum[2][3], counts[2], group, i, j, iteration, distance;
u_int maximum = 0, first = 0, second = 0;
/* Start with the two most widely separated samples. */
for (i = 0; i < count; i++) {
for (j = i + 1; j < count; j++) {
distance = image_glyph_distance(samples[i], samples[j]);
@@ -155,6 +165,8 @@ image_glyph_fit_colours(const struct image_rgb *samples, u_int count,
}
centres[0] = samples[first];
centres[1] = samples[second];
/* Refine the foreground and background by averaging each cluster. */
for (iteration = 0; iteration < 4; iteration++) {
memset(sum, 0, sizeof sum);
memset(counts, 0, sizeof counts);
@@ -176,11 +188,12 @@ image_glyph_fit_colours(const struct image_rgb *samples, u_int count,
}
}
/* Copy the UTF-8 character for an ACS key into a fallback cell. */
static int
image_glyph_set_acs(struct tty *tty, struct utf8_data *data, u_char key)
{
struct utf8_data *ud;
const char *s = tty_acs_get(tty, key);
const char *s = tty_acs_get(tty, key);
if (s == NULL)
return (0);
@@ -194,6 +207,7 @@ image_glyph_set_acs(struct tty *tty, struct utf8_data *data, u_char key)
return (1);
}
/* Map a block's foreground mask to a half, quadrant or sextant glyph. */
static u_char
image_glyph_block_key(enum image_glyph_detail detail, u_int mask)
{
@@ -234,6 +248,7 @@ image_glyph_block_key(enum image_glyph_detail detail, u_int mask)
return (key);
}
/* Build and cache dithered brightness levels for a shading palette. */
static u_char *
image_glyph_make_shades(struct image *im, u_int levels)
{
@@ -250,6 +265,8 @@ image_glyph_make_shades(struct image *im, u_int levels)
result = (levels == 5 ? data->shade5 : data->shade8);
if (result != NULL)
return (result);
/* Collect cell brightness and the range used by this image. */
cells = (size_t)im->sx * im->sy;
values = xcalloc(cells, sizeof *values);
result = xcalloc(cells, 1);
@@ -265,11 +282,15 @@ image_glyph_make_shades(struct image *im, u_int levels)
values[index] = value;
}
}
/* Stretch the brightness range to make all shading levels available. */
if (maximum > minimum) {
for (index = 0; index < cells; index++)
for (index = 0; index < cells; index++) {
values[index] = (values[index] - minimum) * 255 /
(maximum - minimum);
}
}
/* Dither each row, alternating direction to distribute the error. */
for (y = 0; y < im->sy; y++) {
reverse = (y & 1);
for (scan = 0; scan < im->sx; scan++) {
@@ -302,6 +323,8 @@ image_glyph_make_shades(struct image *im, u_int levels)
}
}
free(values);
/* Keep the result for subsequent redraws at the same shading level. */
if (levels == 5)
data->shade5 = result;
else
@@ -309,10 +332,11 @@ image_glyph_make_shades(struct image *im, u_int levels)
return (result);
}
/* Choose the richest colour palette supported by this terminal. */
static enum image_glyph_palette
image_glyph_get_palette(struct tty *tty)
{
int colours;
int colours;
if (tty->term->flags & TERM_RGBCOLOURS)
return (IMAGE_GLYPH_PALETTE_RGB);
@@ -326,6 +350,7 @@ image_glyph_get_palette(struct tty *tty)
return (IMAGE_GLYPH_PALETTE_8);
}
/* Choose the fallback glyph detail supported by this terminal. */
static enum image_glyph_detail
image_glyph_get_detail(struct tty *tty, enum image_glyph_palette palette)
{
@@ -342,6 +367,7 @@ image_glyph_get_detail(struct tty *tty, enum image_glyph_palette palette)
return (IMAGE_GLYPH_SHADE8);
}
/* Render one image cell using a two-colour block glyph. */
static void
image_glyph_block(struct tty *tty, struct image *im, u_int x, u_int y,
enum image_glyph_detail detail, enum image_glyph_palette palette,
@@ -354,6 +380,7 @@ image_glyph_block(struct tty *tty, struct image *im, u_int x, u_int y,
int colours[2];
u_char key;
/* Average the stored samples into the chosen glyph's subcells. */
columns = (detail == IMAGE_GLYPH_HALF ? 1 : 2);
rows = (detail == IMAGE_GLYPH_SEXTANT ? 3 : 2);
i = 0;
@@ -378,6 +405,8 @@ image_glyph_block(struct tty *tty, struct image *im, u_int x, u_int y,
i++;
}
}
/* Fit the two colours and choose which subcells use the foreground. */
n = columns * rows;
image_glyph_fit_colours(samples, n, centres);
quantized[0] = image_glyph_quantize(centres[0], palette, &colours[0]);
@@ -385,10 +414,13 @@ image_glyph_block(struct tty *tty, struct image *im, u_int x, u_int y,
mask = 0;
for (i = 0; i < n; i++) {
if (image_glyph_distance(samples[i], quantized[1]) <
image_glyph_distance(samples[i], quantized[0]))
image_glyph_distance(samples[i], quantized[0])) {
mask |= (1U << i);
}
}
key = image_glyph_block_key(detail, mask);
/* Use a blank cell if the terminal has no matching glyph. */
if (key == 0)
utf8_set(&out->data, ' ');
else if (!image_glyph_set_acs(tty, &out->data, key))
@@ -397,6 +429,7 @@ image_glyph_block(struct tty *tty, struct image *im, u_int x, u_int y,
out->bg = colours[0];
}
/* Render an image cell using the terminal's text and colour capabilities. */
void
image_get_fallback_cell(struct tty *tty, struct image *im, u_int x, u_int y,
const struct grid_cell *gc, struct grid_cell *out)
@@ -414,7 +447,7 @@ image_get_fallback_cell(struct tty *tty, struct image *im, u_int x, u_int y,
enum image_glyph_palette palette;
enum image_glyph_detail detail;
u_char *levels, key;
u_int level = 0;
u_int level = 0, nlevels;
memcpy(out, gc, sizeof *out);
cell = image_get_cell(im, x, y);
@@ -422,6 +455,8 @@ image_get_fallback_cell(struct tty *tty, struct image *im, u_int x, u_int y,
utf8_set(&out->data, ' ');
return;
}
/* Select the palette and glyph detail for this terminal. */
palette = image_glyph_get_palette(tty);
detail = image_glyph_get_detail(tty, palette);
if (detail == IMAGE_GLYPH_ASCII) {
@@ -430,8 +465,10 @@ image_get_fallback_cell(struct tty *tty, struct image *im, u_int x, u_int y,
return;
}
if (detail == IMAGE_GLYPH_SHADE5 || detail == IMAGE_GLYPH_SHADE8) {
levels = image_glyph_make_shades(im,
detail == IMAGE_GLYPH_SHADE5 ? 5 : 8);
nlevels = 8;
if (detail == IMAGE_GLYPH_SHADE5)
nlevels = 5;
levels = image_glyph_make_shades(im, nlevels);
level = levels[(size_t)y * im->sx + x];
key = (detail == IMAGE_GLYPH_SHADE5 ? shades[level] :
bold_shades[level]);
@@ -443,13 +480,15 @@ image_get_fallback_cell(struct tty *tty, struct image *im, u_int x, u_int y,
out->bg = 0;
out->attr &= ~GRID_ATTR_BRIGHT;
if (detail == IMAGE_GLYPH_SHADE8 &&
(level == 2 || level == 4 || level == 7))
(level == 2 || level == 4 || level == 7)) {
out->attr |= GRID_ATTR_BRIGHT;
}
return;
}
image_glyph_block(tty, im, x, y, detail, palette, out);
}
/* Free the brightness levels cached for text image rendering. */
void
image_free_fallback(struct image *im)
{