Use spng to load thumbnails

Speed matters here, and this makes us about 20 percent faster
at loading large directories.

Moreover, libpng's PNG_ALPHA_BROKEN is indeed broken.

Thumbnails have a fairly fixed format, so there are very few practical
corner cases that could have been missed.
This commit is contained in:
Přemysl Eric Janouch 2021-11-12 10:37:02 +01:00
parent afc08df234
commit 21b110a7d6
Signed by: p
GPG Key ID: A0420B94F92B9493
3 changed files with 106 additions and 115 deletions

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@ -18,7 +18,7 @@ a package with the latest development version from Archlinux's AUR.
Building and Running
--------------------
Build dependencies: Meson, pkg-config +
Runtime dependencies: gtk+-3.0, pixman-1, shared-mime-info, libpng>=1.5.4,
Runtime dependencies: gtk+-3.0, pixman-1, shared-mime-info, spng>=0.7.0,
libturbojpeg, LibRaw (optional), librsvg-2.0 (optional),
gdk-pixbuf-2.0 (optional)

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@ -603,53 +603,48 @@ fastiv_io_open_from_data(const char *data, size_t len, const gchar *path,
// NOTE: "It is important to note that when an image with an alpha channel is
// scaled, linear encoded, pre-multiplied component values must be used!"
#include <glib/gstdio.h>
#include <png.h>
#include <spng.h>
static void
redirect_png_error(png_structp pngp, const char *error)
{
set_error(png_get_error_ptr(pngp), error);
png_longjmp(pngp, 1);
}
static void
discard_png_warning(png_structp pngp, const char *warning)
{
(void) pngp;
(void) warning;
}
static int
check_png_thumbnail(
png_structp pngp, png_infop infop, const gchar *target, time_t mtime)
static int // tri-state
check_spng_thumbnail_texts(struct spng_text *texts, uint32_t texts_len,
const gchar *target, time_t mtime)
{
// May contain Thumb::Image::Width Thumb::Image::Height,
// but those aren't interesting currently (would be for fast previews).
int texts_len = 0;
png_textp texts = NULL;
png_get_text(pngp, infop, &texts, &texts_len);
gboolean need_uri = TRUE, need_mtime = TRUE;
for (int i = 0; i < texts_len; i++) {
png_textp text = texts + i;
if (!strcmp(text->key, "Thumb::URI")) {
need_uri = FALSE;
bool need_uri = true, need_mtime = true;
for (uint32_t i = 0; i < texts_len; i++) {
struct spng_text *text = texts + i;
if (!strcmp(text->keyword, "Thumb::URI")) {
need_uri = false;
if (strcmp(target, text->text))
return FALSE;
return false;
}
if (!strcmp(text->key, "Thumb::MTime")) {
need_mtime = FALSE;
if (!strcmp(text->keyword, "Thumb::MTime")) {
need_mtime = false;
if (atol(text->text) != mtime)
return FALSE;
return false;
}
}
return need_uri || need_mtime ? -1 : TRUE;
return need_uri || need_mtime ? -1 : true;
}
static int // tri-state
check_spng_thumbnail(spng_ctx *ctx, const gchar *target, time_t mtime, int *err)
{
uint32_t texts_len = 0;
if ((*err = spng_get_text(ctx, NULL, &texts_len)))
return false;
int result = false;
struct spng_text *texts = g_malloc0_n(texts_len, sizeof *texts);
if (!(*err = spng_get_text(ctx, texts, &texts_len)))
result = check_spng_thumbnail_texts(texts, texts_len, target, mtime);
g_free(texts);
return result;
}
// TODO(p): Support spng as well (it can't premultiply alpha by itself,
// but at least it won't gamma-adjust it for us).
static cairo_surface_t *
read_png_thumbnail(
read_spng_thumbnail(
const gchar *path, const gchar *uri, time_t mtime, GError **error)
{
FILE *fp;
@ -658,96 +653,92 @@ read_png_thumbnail(
return NULL;
}
cairo_surface_t *volatile surface = NULL;
png_structp pngp = png_create_read_struct(
PNG_LIBPNG_VER_STRING, error, redirect_png_error, discard_png_warning);
png_infop infop = png_create_info_struct(pngp);
if (!infop) {
cairo_surface_t *result = NULL;
errno = 0;
spng_ctx *ctx = spng_ctx_new(0);
if (!ctx) {
set_error(error, g_strerror(errno));
goto fail_preread;
goto fail_init;
}
volatile png_bytepp row_pointers = NULL;
if (setjmp(png_jmpbuf(pngp))) {
if (surface) {
cairo_surface_destroy(surface);
surface = NULL;
}
int err;
size_t size = 0;
if ((err = spng_set_png_file(ctx, fp)) ||
(err = spng_set_image_limits(ctx, INT16_MAX, INT16_MAX)) ||
(err = spng_decoded_image_size(ctx, SPNG_FMT_RGBA8, &size))) {
set_error(error, spng_strerror(err));
goto fail;
}
if (check_spng_thumbnail(ctx, uri, mtime, &err) == false) {
set_error(error, err ? spng_strerror(err) : "mismatch");
goto fail;
}
png_init_io(pngp, fp);
// XXX: libpng will premultiply with the alpha, but it also gamma-adjust it.
png_set_alpha_mode(pngp, PNG_ALPHA_BROKEN, PNG_DEFAULT_sRGB);
png_read_info(pngp, infop);
if (check_png_thumbnail(pngp, infop, uri, mtime) == FALSE)
png_error(pngp, "mismatch");
// Asking for at least 8-bit channels. This call is a superset of:
// - png_set_palette_to_rgb(),
// - png_set_tRNS_to_alpha(),
// - png_set_expand_gray_1_2_4_to_8().
png_set_expand(pngp);
// Reduce the possibilities further to RGB or RGBA...
png_set_gray_to_rgb(pngp);
// ...and /exactly/ 8-bit channels.
// Alternatively, use png_set_expand_16() above to obtain 16-bit channels.
png_set_scale_16(pngp);
// PNG uses RGBA order, we want either ARGB (BE) or BGRA (LE).
if (G_BYTE_ORDER == G_LITTLE_ENDIAN) {
png_set_bgr(pngp);
png_set_add_alpha(pngp, 0xFFFF, PNG_FILLER_AFTER);
png_set_swap(pngp);
} else {
// This doesn't change a row's `color_type` in png_do_read_filler(),
// and the following transformation thus ignores it.
png_set_add_alpha(pngp, 0xFFFF, PNG_FILLER_BEFORE);
png_set_swap_alpha(pngp);
uint32_t *data = g_malloc0(size);
if ((err = spng_decode_image(ctx, data, size, SPNG_FMT_RGBA8,
SPNG_DECODE_TRNS | SPNG_DECODE_GAMMA))) {
set_error(error, spng_strerror(err));
goto fail_data;
}
(void) png_set_interlace_handling(pngp);
png_read_update_info(pngp, infop);
png_uint_32 w = png_get_image_width(pngp, infop);
png_uint_32 h = png_get_image_height(pngp, infop);
if (w > INT16_MAX || h > INT16_MAX)
png_error(pngp, "the image is too large");
surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, w, h);
cairo_status_t surface_status = cairo_surface_status(surface);
if (surface_status != CAIRO_STATUS_SUCCESS)
png_error(pngp, cairo_status_to_string(surface_status));
size_t row_bytes = png_get_rowbytes(pngp, infop);
g_assert((size_t) cairo_image_surface_get_stride(surface) == row_bytes);
unsigned char *buffer = cairo_image_surface_get_data(surface);
png_uint_32 height = png_get_image_height(pngp, infop);
if (!(row_pointers = calloc(height, sizeof *row_pointers)))
png_error(pngp, g_strerror(errno));
for (size_t y = 0; y < height; y++)
row_pointers[y] = buffer + y * row_bytes;
cairo_surface_flush(surface);
png_read_image(pngp, row_pointers);
cairo_surface_mark_dirty(surface);
// The specification does not say where the required metadata should be,
// it could very well be broken up into two parts.
png_read_end(pngp, infop);
if (check_png_thumbnail(pngp, infop, uri, mtime) != TRUE)
png_error(pngp, "mismatch or not a thumbnail");
if (check_spng_thumbnail(ctx, uri, mtime, &err) != true) {
set_error(
error, err ? spng_strerror(err) : "mismatch or not a thumbnail");
goto fail_data;
}
struct spng_ihdr ihdr = {};
spng_get_ihdr(ctx, &ihdr);
cairo_surface_t *surface = cairo_image_surface_create(
CAIRO_FORMAT_ARGB32, ihdr.width, ihdr.height);
cairo_status_t surface_status = cairo_surface_status(surface);
if (surface_status != CAIRO_STATUS_SUCCESS) {
set_error(error, cairo_status_to_string(surface_status));
cairo_surface_destroy(surface);
goto fail_data;
}
g_assert((size_t) cairo_image_surface_get_stride(surface) *
cairo_image_surface_get_height(surface) == size);
// pixman can be mildly abused to do this operation, but it won't be faster.
uint32_t *output = (uint32_t *) cairo_image_surface_get_data(surface);
cairo_surface_flush(surface);
struct spng_trns trns = {};
if (ihdr.color_type == SPNG_COLOR_TYPE_GRAYSCALE_ALPHA ||
ihdr.color_type == SPNG_COLOR_TYPE_TRUECOLOR_ALPHA ||
!spng_get_trns(ctx, &trns)) {
for (size_t i = size / sizeof *output; i--; ) {
uint8_t *unit = (uint8_t *) &data[i],
a = unit[3],
b = unit[2] * a / 255,
g = unit[1] * a / 255,
r = unit[0] * a / 255;
output[i] = a << 24 | r << 16 | g << 8 | b;
}
} else {
for (size_t i = size / sizeof *output; i--; ) {
uint8_t *unit = (uint8_t *) &data[i],
a = unit[3],
b = unit[2],
g = unit[1],
r = unit[0];
output[i] = a << 24 | r << 16 | g << 8 | b;
}
}
cairo_surface_mark_dirty((result = surface));
fail_data:
free(data);
fail:
free(row_pointers);
fail_preread:
png_destroy_read_struct(&pngp, &infop, NULL);
spng_ctx_free(ctx);
fail_init:
fclose(fp);
return surface;
return result;
}
cairo_surface_t *
@ -772,7 +763,7 @@ fastiv_io_lookup_thumbnail(const gchar *target)
for (gsize i = 0; !result && i < G_N_ELEMENTS(sizes); i++) {
gchar *path = g_strdup_printf(
"%s/thumbnails/%s/%s.png", cache_dir, sizes[i], sum);
result = read_png_thumbnail(path, uri, st.st_mtim.tv_sec, &error);
result = read_spng_thumbnail(path, uri, st.st_mtim.tv_sec, &error);
if (error) {
g_debug("%s: %s", path, error->message);
g_clear_error(&error);

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@ -7,7 +7,7 @@ gdkpixbuf = dependency('gdk-pixbuf-2.0', required : get_option('gdk-pixbuf'))
dependencies = [
dependency('gtk+-3.0'),
dependency('libturbojpeg'),
dependency('libpng', version : '>=1.5.4'),
dependency('spng', version : '>=0.7.0'),
dependency('pixman-1'),
libraw,
librsvg,