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Read Exif and ICC profile metadata from JPEGs

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This commit is contained in:
Přemysl Eric Janouch 2021-11-23 21:48:14 +01:00
parent c597e7bc2c
commit 2ea2178724
Signed by: p
GPG Key ID: A0420B94F92B9493
2 changed files with 94 additions and 0 deletions
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91
fastiv-io.c
View File

@ -361,6 +361,93 @@ trivial_cmyk_to_bgra(unsigned char *p, int len)
}
}
static void
parse_jpeg_metadata(cairo_surface_t *surface, const gchar *data, gsize len)
{
// Because the JPEG file format is simple, just do it manually.
// See: https://www.w3.org/Graphics/JPEG/itu-t81.pdf
enum {
APP0 = 0xE0,
APP1,
APP2,
RST0 = 0xD0,
RST1,
RST2,
RST3,
RST4,
RST5,
RST6,
RST7,
SOI = 0xD8,
EOI = 0xD9,
SOS = 0xDA,
TEM = 0x01,
};
GByteArray *exif = g_byte_array_new(), *icc = g_byte_array_new();
int icc_sequence = 0, icc_done = FALSE;
const guint8 *p = (const guint8 *) data, *end = p + len;
while (p + 3 < end && *p++ == 0xFF && *p != SOS && *p != EOI) {
// The previous byte is a fill byte, restart.
if (*p == 0xFF)
continue;
// These markers stand alone, not starting a marker segment.
guint8 marker = *p++;
switch (marker) {
case RST0:
case RST1:
case RST2:
case RST3:
case RST4:
case RST5:
case RST6:
case RST7:
case SOI:
case TEM:
continue;
}
// Do not bother validating the structure.
guint16 length = p[0] << 8 | p[1];
const guint8 *payload = p + 2;
if ((p += length) > end)
break;
// https://www.cipa.jp/std/documents/e/DC-008-2012_E.pdf 4.7.2
// Do not check the padding byte.
if (marker == APP1 && p - payload >= 6 &&
!memcmp(payload, "Exif\0", 5) && !exif->len) {
payload += 6;
g_byte_array_append(exif, payload, p - payload);
}
// https://www.color.org/specification/ICC1v43_2010-12.pdf B.4
if (marker == APP2 && p - payload >= 14 &&
!memcmp(payload, "ICC_PROFILE\0", 12) && !icc_done &&
payload[12] == ++icc_sequence && payload[13] >= payload[12]) {
payload += 14;
g_byte_array_append(icc, payload, p - payload);
icc_done = payload[-1] == icc_sequence;
}
}
if (exif->len)
cairo_surface_set_user_data(surface, &fastiv_io_key_exif,
g_byte_array_free_to_bytes(exif),
(cairo_destroy_func_t) g_byte_array_unref);
else
g_byte_array_free(exif, TRUE);
if (icc_done)
cairo_surface_set_user_data(surface, &fastiv_io_key_icc,
g_byte_array_free_to_bytes(icc),
(cairo_destroy_func_t) g_byte_array_unref);
else
g_byte_array_free(icc, TRUE);
}
static cairo_surface_t *
open_libjpeg_turbo(const gchar *data, gsize len, GError **error)
{
@ -417,6 +504,7 @@ open_libjpeg_turbo(const gchar *data, gsize len, GError **error)
cairo_surface_mark_dirty(surface);
tjDestroy(dec);
parse_jpeg_metadata(surface, data, len);
return surface;
}
@ -764,6 +852,9 @@ open_gdkpixbuf(const gchar *data, gsize len, GError **error)
#endif // HAVE_GDKPIXBUF ------------------------------------------------------
cairo_user_data_key_t fastiv_io_key_exif;
cairo_user_data_key_t fastiv_io_key_icc;
cairo_surface_t *
fastiv_io_open(const gchar *path, GError **error)
{

3
fastiv-io.h
View File

@ -52,6 +52,9 @@ typedef struct _FastivIoThumbnailSizeInfo {
extern FastivIoThumbnailSizeInfo
fastiv_io_thumbnail_sizes[FASTIV_IO_THUMBNAIL_SIZE_COUNT];
extern cairo_user_data_key_t fastiv_io_key_exif;
extern cairo_user_data_key_t fastiv_io_key_icc;
cairo_surface_t *fastiv_io_open(const gchar *path, GError **error);
cairo_surface_t *fastiv_io_open_from_data(
const char *data, size_t len, const gchar *path, GError **error);