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sixel: implement P2=1 - transparent pixels

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When P2=1, empty pixels are transparent.

This patch also changes the behavior of P2=0|2, from setting empty
pixels to the default background color, to instead use the *current*
background color.

To implement this, a couple of changes are needed:

* Sixel pixels always use alpha=1.0, except for *empty* cells when
  P2=1 (i.e. transparent pixels).
* The renderer draws sixels with the OVER operator, instead of the SRC
  operator.
* The renderer *must* now render the cells beneath the sixel. As an
  optimization, this is only done for sixels where P2=1. I.e. for
  fully opaque sixels, there’s no need to render the cells beneath.

The sixel renderer isn’t yet hooked into the multi-threaded
renderer. This means *rows* (not just the cells) beneath
maybe-transparent sixels are rendered single-threaded.

Closes #391.
This commit is contained in:
Daniel Eklöf 2021-03-09 17:23:55 +01:00
parent 5650120e08
commit 7d315d7bf9
No known key found for this signature in database
GPG key ID: 5BBD4992C116573F
5 changed files with 91 additions and 50 deletions
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53
sixel.c
View file

@ -15,6 +15,16 @@
static size_t count;
static uint32_t
get_bg(const struct terminal *term)
{
return term->sixel.transparent_bg
? 0x00000000u
: 0xffu << 24 | (term->vt.attrs.have_bg
? term->vt.attrs.bg
: term->colors.bg);
}
void
sixel_fini(struct terminal *term)
{
@ -22,16 +32,17 @@ sixel_fini(struct terminal *term)
free(term->sixel.shared_palette);
}
static uint32_t
color_with_alpha(const struct terminal *term, uint32_t color)
{
uint16_t alpha = color == term->colors.bg ? term->colors.alpha : 0xffff;
return (alpha / 256u) << 24 | color;
}
void
sixel_init(struct terminal *term)
sixel_init(struct terminal *term, int p1, int p2, int p3)
{
/*
* P1: pixel aspect ratio - unimplemented
* P2: background color mode
* - 0|2: empty pixels use current background color
* - 1: empty pixels remain at their current color (i.e. transparent)
* P3: horizontal grid size - ignored
*/
xassert(term->sixel.image.data == NULL);
xassert(term->sixel.palette_size <= SIXEL_MAX_COLORS);
@ -43,6 +54,7 @@ sixel_init(struct terminal *term)
term->sixel.param = 0;
term->sixel.param_idx = 0;
memset(term->sixel.params, 0, sizeof(term->sixel.params));
term->sixel.transparent_bg = p2 == 1;
term->sixel.image.data = xmalloc(1 * 6 * sizeof(term->sixel.image.data[0]));
term->sixel.image.width = 1;
term->sixel.image.height = 6;
@ -65,8 +77,9 @@ sixel_init(struct terminal *term)
term->sixel.palette = term->sixel.shared_palette;
}
uint32_t bg = get_bg(term);
for (size_t i = 0; i < 1 * 6; i++)
term->sixel.image.data[i] = color_with_alpha(term, term->colors.bg);
term->sixel.image.data[i] = bg;
count = 0;
}
@ -106,7 +119,7 @@ sixel_erase(struct terminal *term, struct sixel *sixel)
row->dirty = true;
for (int c = 0; c < term->grid->num_cols; c++)
for (int c = sixel->pos.col; c < min(sixel->cols, term->cols); c++)
row->cells[c].attrs.clean = 0;
}
@ -421,6 +434,7 @@ sixel_overwrite(struct terminal *term, struct sixel *six,
.pos = {.col = new_col, .row = new_row},
.cols = (new_width + term->cell_width - 1) / term->cell_width,
.rows = (new_height + term->cell_height - 1) / term->cell_height,
.opaque = six->opaque,
};
#if defined(_DEBUG)
@ -767,6 +781,7 @@ sixel_unhook(struct terminal *term)
.rows = (height + term->cell_height - 1) / term->cell_height,
.cols = (width + term->cell_width - 1) / term->cell_width,
.pos = (struct coord){start_col, cur_row},
.opaque = !term->sixel.transparent_bg,
};
xassert(image.rows < term->grid->num_rows);
@ -868,6 +883,8 @@ resize_horizontally(struct terminal *term, int new_width)
/* Width (and thus stride) change - need to allocate a new buffer */
uint32_t *new_data = xmalloc(new_width * alloc_height * sizeof(uint32_t));
uint32_t bg = get_bg(term);
/* Copy old rows, and initialize new columns to background color */
for (int r = 0; r < height; r++) {
memcpy(&new_data[r * new_width],
@ -875,7 +892,7 @@ resize_horizontally(struct terminal *term, int new_width)
old_width * sizeof(uint32_t));
for (int c = old_width; c < new_width; c++)
new_data[r * new_width + c] = color_with_alpha(term, term->colors.bg);
new_data[r * new_width + c] = bg;
}
free(old_data);
@ -915,10 +932,12 @@ resize_vertically(struct terminal *term, int new_height)
return false;
}
uint32_t bg = get_bg(term);
/* Initialize new rows to background color */
for (int r = old_height; r < new_height; r++) {
for (int c = 0; c < width; c++)
new_data[r * width + c] = color_with_alpha(term, term->colors.bg);
new_data[r * width + c] = bg;
}
term->sixel.image.data = new_data;
@ -950,6 +969,7 @@ resize(struct terminal *term, int new_width, int new_height)
xassert(alloc_new_height - new_height < 6);
uint32_t *new_data = NULL;
uint32_t bg = get_bg(term);
if (new_width == old_width) {
/* Width (and thus stride) is the same, so we can simply
@ -973,7 +993,7 @@ resize(struct terminal *term, int new_width, int new_height)
memcpy(&new_data[r * new_width], &old_data[r * old_width], old_width * sizeof(uint32_t));
for (int c = old_width; c < new_width; c++)
new_data[r * new_width + c] = color_with_alpha(term, term->colors.bg);
new_data[r * new_width + c] = bg;
}
free(old_data);
}
@ -981,7 +1001,7 @@ resize(struct terminal *term, int new_width, int new_height)
/* Initialize new rows to background color */
for (int r = old_height; r < new_height; r++) {
for (int c = 0; c < new_width; c++)
new_data[r * new_width + c] = color_with_alpha(term, term->colors.bg);
new_data[r * new_width + c] = bg;
}
xassert(new_data != NULL);
@ -1239,8 +1259,7 @@ decgci(struct terminal *term, uint8_t c)
LOG_DBG("setting palette #%d = HLS %hhu/%hhu/%hhu (0x%06x)",
term->sixel.color_idx, hue, lum, sat, rgb);
term->sixel.palette[term->sixel.color_idx] =
color_with_alpha(term, rgb);
term->sixel.palette[term->sixel.color_idx] = 0xffu << 24 | rgb;
break;
}
@ -1253,7 +1272,7 @@ decgci(struct terminal *term, uint8_t c)
term->sixel.color_idx, r, g, b);
term->sixel.palette[term->sixel.color_idx] =
color_with_alpha(term, r << 16 | g << 8 | b);
0xffu << 24 | r << 16 | g << 8 | b;
break;
}
}