exif.c

Gqview,Linux下基于GTK+库写成的轻量级而能丰富的图像浏览程序。

		if (format_raw_img_exif_offsets(f, size, NULL, &offset))
			{
			res = exif_tiff_parse(exif, (unsigned char*)f + offset, size - offset, ExifKnownMarkersList);
			}
		}

	if (res != 0)
		{
		exif_free(exif);
		exif = NULL;
		}

	unmap_file(f, size);

	if (exif) exif->items = g_list_reverse(exif->items);

#if 0
	exif_write_data_list(exif, stdout, TRUE);
	exif_write_data_list(exif, stdout, FALSE);
#endif

	return exif;
}

ExifItem *exif_get_item(ExifData *exif, const gchar *key)
{
	GList *work;

	if (!key) return NULL;

	work = exif->items;
	while (work)
 		{
		ExifItem *item;

		item = work->data;
		work = work->next;
		if (item->marker->key && strcmp(key, item->marker->key) == 0) return item;
                }
	return NULL;
}

gchar *exif_item_get_data_as_text(ExifItem *item)
{
	const ExifMarker *marker;
	gpointer data;
	GString *string;
	gchar *text;
	gint ne;
	gint i;

	if (!item) return NULL;

	marker = item->marker;
	if (!marker) return NULL;

	data = item->data;
	ne = item->elements;
	string = g_string_new("");
	switch (item->format)
		{
		case EXIF_FORMAT_UNKNOWN:
			break;
		case EXIF_FORMAT_BYTE_UNSIGNED:
		case EXIF_FORMAT_BYTE:
		case EXIF_FORMAT_UNDEFINED:
			if (ne == 1 && marker->list)
				{
				gchar *result;
				unsigned char val;

				if (item->format == EXIF_FORMAT_BYTE_UNSIGNED ||
				    item->format == EXIF_FORMAT_UNDEFINED)
					{
					val = ((unsigned char *)data)[0];
					}
				else
					{
					val = (unsigned char)(((signed char *)data)[0]);
					}

				result = exif_text_list_find_value(marker->list, (guint)val);
				string = g_string_append(string, result);
				g_free(result);
				}
			else
				{
				string = string_append_raw_bytes(string, data, ne);
				}
			break;
		case EXIF_FORMAT_STRING:
			string = g_string_append(string, (gchar *)(item->data));
			break;
		case EXIF_FORMAT_SHORT_UNSIGNED:
			if (ne == 1 && marker->list)
				{
				gchar *result;

				result = exif_text_list_find_value(marker->list, ((unsigned short *)data)[0]);
				string = g_string_append(string, result);
				g_free(result);
				}
			else for (i = 0; i < ne; i++)
				{
				g_string_append_printf(string, "%s%hd", (i > 0) ? ", " : "",
							((unsigned short *)data)[i]);
				}
			break;
		case EXIF_FORMAT_LONG_UNSIGNED:
			for (i = 0; i < ne; i++)
				{
				g_string_append_printf(string, "%s%ld", (i > 0) ? ", " : "",
							((unsigned long *)data)[i]);
				}
			break;
		case EXIF_FORMAT_RATIONAL_UNSIGNED:
			for (i = 0; i < ne; i++)
				{
				ExifRational *r;

				r = &((ExifRational *)data)[i];
				g_string_append_printf(string, "%s%ld/%ld", (i > 0) ? ", " : "",
							(unsigned long)r->num, (unsigned long)r->den);
				}
			break;
		case EXIF_FORMAT_SHORT:
			for (i = 0; i < ne; i++)
				{
				g_string_append_printf(string, "%s%hd", (i > 0) ? ", " : "",
							((short *)data)[i]);
				}
			break;
		case EXIF_FORMAT_LONG:
			for (i = 0; i < ne; i++)
				{
				g_string_append_printf(string, "%s%ld", (i > 0) ? ", " : "",
							((long *)data)[i]);
				}
			break;
		case EXIF_FORMAT_RATIONAL:
			for (i = 0; i < ne; i++)
				{
				ExifRational *r;

				r = &((ExifRational *)data)[i];
				g_string_append_printf(string, "%s%ld/%ld", (i > 0) ? ", " : "",
							(long)r->num, (long)r->den);
				}
			break;
		case EXIF_FORMAT_FLOAT:
			for (i = 0; i < ne; i++)
				{
				g_string_append_printf(string, "%s%f", (i > 0) ? ", " : "",
							((float *)data)[i]);
				}
			break;
		case EXIF_FORMAT_DOUBLE:
			for (i = 0; i < ne; i++)
				{
				g_string_append_printf(string, "%s%f", (i > 0) ? ", " : "",
							((double *)data)[i]);
				}
			break;
		}

	text = g_strdup(string->str);
	g_string_free(string, TRUE);

	return text;
}

gint exif_item_get_integer(ExifItem *item, gint *value)
{
	if (!item) return FALSE;

	switch (item->format)
		{
		case EXIF_FORMAT_SHORT:
			*value = (gint)(((short *)(item->data))[0]);
			return TRUE;
			break;
		case EXIF_FORMAT_SHORT_UNSIGNED:
			*value = (gint)(((unsigned short *)(item->data))[0]);
			return TRUE;
			break;
		case EXIF_FORMAT_LONG:
			*value = (gint)(((long *)(item->data))[0]);
			return TRUE;
			break;
		case EXIF_FORMAT_LONG_UNSIGNED:
			/* FIXME: overflow possible */
			*value = (gint)(((unsigned long *)(item->data))[0]);
			return TRUE;
		default:
			/* all other type return FALSE */
			break;
		}
	return FALSE;
}

gint exif_get_integer(ExifData *exif, const gchar *key, gint *value)
{
	ExifItem *item;

	item = exif_get_item(exif, key);
	return exif_item_get_integer(item, value);
}

ExifRational *exif_item_get_rational(ExifItem *item, gint *sign)
{
	if (!item) return NULL;

	if (item->format == EXIF_FORMAT_RATIONAL ||
	    item->format == EXIF_FORMAT_RATIONAL_UNSIGNED)
		{
		if (sign) *sign = (item->format == EXIF_FORMAT_RATIONAL);
		return &((ExifRational *)(item->data))[0];
		}

	return NULL;
}

ExifRational *exif_get_rational(ExifData *exif, const gchar *key, gint *sign)
{
	ExifItem *item;

	item = exif_get_item(exif, key);
	return exif_item_get_rational(item, sign);
}

double exif_rational_to_double(ExifRational *r, gint sign)
{
	if (!r || r->den == 0.0) return 0.0;

	if (sign) return (double)((int)r->num) / (double)((int)r->den);
	return (double)r->num / r->den;
}

static double exif_get_rational_as_double(ExifData *exif, const gchar *key)
{
	ExifRational *r;
	gint sign;

	r = exif_get_rational(exif, key, &sign);
	return exif_rational_to_double(r, sign);
}

static GString *append_comma_text(GString *string, const gchar *text)
{
	string = g_string_append(string, ", ");
	string = g_string_append(string, text);

	return string;
}

static gchar *exif_get_formatted_by_key(ExifData *exif, const gchar *key, gint *key_valid)
{
	/* must begin with f, else not formatted */
	if (key[0] != 'f')
		{
		if (key_valid) *key_valid = FALSE;
		return NULL;
		}

	if (key_valid) *key_valid = TRUE;

	if (strcmp(key, "fCamera") == 0)
		{
		gchar *text;
		gchar *make = exif_get_data_as_text(exif, "Make");
		gchar *model = exif_get_data_as_text(exif, "Model");
		gchar *software = exif_get_data_as_text(exif, "Software");

		text = g_strdup_printf("%s%s%s%s%s%s", (make) ? make : "", ((make) && (model)) ? " " : "",
						       (model) ? model : "",
						       (software) ? " (" : "",
						       (software) ? software : "",
						       (software) ? ")" : "");

		g_free(make);
		g_free(model);
		g_free(software);
		return text;
		}
	if (strcmp(key, "fDateTime") == 0)
		{
		gchar *text = exif_get_data_as_text(exif, "DateTimeOriginal");
		gchar *subsec = NULL;
		if (text) subsec = exif_get_data_as_text(exif, "SubsecTimeOriginal");
		if (!text)
			{
			text = exif_get_data_as_text(exif, "DateTime");
			if (text) subsec = exif_get_data_as_text(exif, "SubsecTime");
			}
		if (subsec)
			{
			gchar *tmp = text;
			text = g_strconcat(tmp, ".", subsec, NULL);
			g_free(tmp);
			g_free(subsec);
			}
		return text;
		}
	if (strcmp(key, "fShutterSpeed") == 0)
		{
		ExifRational *r;

		r = exif_get_rational(exif, "ExposureTime", NULL);
		if (r && r->num && r->den)
			{
			double n = (double)r->den / (double)r->num;
			return g_strdup_printf("%s%.0fs", n > 1.0 ? "1/" : "",
							  n > 1.0 ? n : 1.0 / n);
			}
		r = exif_get_rational(exif, "ShutterSpeedValue", NULL);
		if (r && r->num  && r->den)
			{
			double n = pow(2.0, exif_rational_to_double(r, TRUE));

			/* Correct exposure time to avoid values like 1/91s (seen on Minolta DImage 7) */
			if (n > 1.0 && (int)n - ((int)(n/10))*10 == 1) n--;

			return g_strdup_printf("%s%.0fs", n > 1.0 ? "1/" : "",
							  n > 1.0 ? floor(n) : 1.0 / n);	
			}
		return NULL;
		}
	if (strcmp(key, "fAperture") == 0)
		{
		double n;

		n = exif_get_rational_as_double(exif, "FNumber");
		if (n == 0.0) n = exif_get_rational_as_double(exif, "ApertureValue");
		if (n == 0.0) return NULL;

		return g_strdup_printf("f/%.1f", n);
		}
	if (strcmp(key, "fExposureBias") == 0)
		{
		ExifRational *r;
		gint sign;
		double n;

		r = exif_get_rational(exif, "ExposureBiasValue", &sign);
		if (!r) return NULL;

		n = exif_rational_to_double(r, sign);
		return g_strdup_printf("%+.1f", n);
		}
	if (strcmp(key, "fFocalLength") == 0)
		{
		double n;

		n = exif_get_rational_as_double(exif, "FocalLength");
		if (n == 0.0) return NULL;
		return g_strdup_printf("%.2f mm", n);
		}
	if (strcmp(key, "fISOSpeedRating") == 0)
		{
		gchar *text;

		text = exif_get_data_as_text(exif, "ISOSpeedRatings");
		/* kodak may set this instead */
		if (!text) text = exif_get_data_as_text(exif, "ExposureIndex");
		return text;
		}
	if (strcmp(key, "fSubjectDistance") == 0)
		{
		ExifRational *r;
		gint sign;
		double n;

		r = exif_get_rational(exif, "SubjectDistance", &sign);
		if (!r) return NULL;

		if ((long)r->num == 0xffffffff) return g_strdup(_("infinity"));
		if ((long)r->num == 0) return g_strdup(_("unknown"));

		n = exif_rational_to_double(r, sign);
		if (n == 0.0) return _("unknown");
		return g_strdup_printf("%.3f m", n);
		}
	if (strcmp(key, "fFlash") == 0)
		{
		/* grr, flash is a bitmask... */
		GString *string;
		gchar *text;
		gint n;
		gint v;

		if (!exif_get_integer(exif, "Flash", &n)) return NULL;

		/* Exif 2.1 only defines first 3 bits */
		if (n <= 0x07) return exif_text_list_find_value(ExifFlashList, n);

		/* must be Exif 2.2 */
		string = g_string_new("");

		/* flash fired (bit 0) */
		string = g_string_append(string, (n & 0x01) ? _("yes") : _("no"));

		/* flash mode (bits 3, 4) */
		v = (n >> 3) & 0x03;
		if (v) string = append_comma_text(string, _("mode:"));
		switch (v)
			{
			case 1:
				string = g_string_append(string, _("on"));
				break;
			case 2:
				string = g_string_append(string, _("off"));
				break;
			case 3:
				string = g_string_append(string, _("auto"));
				break;
			}

		/* return light (bits 1, 2) */
		v = (n >> 1) & 0x03;
		if (v == 2) string = append_comma_text(string, _("not detected by strobe"));
		if (v == 3) string = append_comma_text(string, _("detected by strobe"));

		/* we ignore flash function (bit 5) */

		/* red-eye (bit 6) */
		if ((n >> 5) & 0x01) string = append_comma_text(string, _("red-eye reduction"));

		text = string->str;
		g_string_free(string, FALSE);
		return text;
		}
	if (strcmp(key, "fResolution") == 0)
		{
		ExifRational *rx, *ry;
		gchar *units;
		gchar *text;

		rx = exif_get_rational(exif, "XResolution", NULL);
		ry = exif_get_rational(exif, "YResolution", NULL);
		if (!rx || !ry) return NULL;

		units = exif_get_data_as_text(exif, "ResolutionUnit");
		text = g_strdup_printf("%0.f x %0.f (%s/%s)", rx->den ? (double)rx->num / rx->den : 1.0,
							      ry->den ? (double)ry->num / ry->den : 1.0,
							      _("dot"), (units) ? units : _("unknown"));

		g_free(units);
		return text;
		}

	if (key_valid) *key_valid = FALSE;
	return NULL;
}

gchar *exif_get_data_as_text(ExifData *exif, const gchar *key)
{
	ExifItem *item;
	gchar *text;
	gint key_valid;

	if (!key) return NULL;

	text = exif_get_formatted_by_key(exif, key, &key_valid);
	if (key_valid) return text;

	item = exif_get_item(exif, key);
	if (item) return exif_item_get_data_as_text(item);

	return NULL;
}

const gchar *exif_get_description_by_key(const gchar *key)
{
	gint i;

	if (!key) return NULL;

	i = 0;
	while (ExifFormattedList[i].key != NULL)
		{
		if (strcmp(key, ExifFormattedList[i].key) == 0) return _(ExifFormattedList[i].description);
		i++;
		}

	i = 0;
	while (ExifKnownMarkersList[i].tag > 0)
		{
		if (strcmp(key, ExifKnownMarkersList[i].key) == 0) return _(ExifKnownMarkersList[i].description);
		i++;
		}

	return NULL;
}

static void exif_write_item(FILE *f, ExifItem *item)
{
	gchar *text;

	text = exif_item_get_data_as_text(item);
	if (text)
		{
		fprintf(f, "%4x %9s %30s %s\n", item->tag, ExifFormatList[item->format].short_name,
			exif_item_get_tag_name(item), text);
		}
	g_free(text);
}

void exif_write_data_list(ExifData *exif, FILE *f, gint human_readable_list)
{
	if (!f || !exif) return;

	fprintf(f, " tag   format                             key value\n");
	fprintf(f, "----------------------------------------------------\n");

	if (human_readable_list)
		{
		gint i;

		i = 0;
		while (ExifFormattedList[i].key)
			{
			gchar *text;

			text = exif_get_formatted_by_key(exif, ExifFormattedList[i].key, NULL);
			if (text)
				{
				fprintf(f, "     %9s %30s %s\n", "string", ExifFormattedList[i].key, text);
				}
			i++;
			}
		}
	else
		{
		GList *work;

		work = exif->items;
		while (work)
			{
			ExifItem *item;

			item = work->data;
			work = work->next;

			exif_write_item(f, item);
			}
		}
	fprintf(f, "----------------------------------------------------\n");
}