File: correlate.c

package info (click to toggle)
gpscorrelate 1.6.1-7
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, buster, sid
  • size: 936 kB
  • sloc: ansic: 1,781; cpp: 440; makefile: 61
file content (322 lines) | stat: -rw-r--r-- 9,855 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
/* correlate.c
 * Written by Daniel Foote.
 * Started Feb 2005.
 *
 * The functions in this file match the timestamps on
 * the photos to the GPS data, and then, if a match
 * is found, writes the GPS data into the EXIF data
 * in the photo. For future reference... */

/* Copyright 2005 Daniel Foote.
 *
 * This file is part of gpscorrelate.
 *
 * gpscorrelate is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * gpscorrelate is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with gpscorrelate; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <stdlib.h>
#include <stdio.h>
#include <time.h>

#include "gpsstructure.h"
#include "exif-gps.h"
#include "correlate.h"
#include "unixtime.h"

/* Internal functions used to make it work. */
void Round(struct GPSPoint* First, struct GPSPoint* Result,
		struct CorrelateOptions* Options, time_t PhotoTime);
void Interpolate(struct GPSPoint* First, struct GPSPoint* Result,
		struct CorrelateOptions* Options, time_t PhotoTime);

/* This function returns a GPSPoint with the point selected for the
 * file. This allows us to do funky stuff like not actually write
 * the files - ie, just correlate and keep into memory... */

struct GPSPoint* CorrelatePhoto(char* Filename,
		struct CorrelateOptions* Options)
{
	/* Read out the timestamp from the EXIF data. */
	char* TimeTemp; int IncludesGPS = 0;
	TimeTemp = ReadExifDate(Filename, &IncludesGPS);
	if (!TimeTemp)
	{
		/* Error reading the time from the file. Abort. */
		/* If this was a read error, then a seperate message
		 * will appear on the console. Otherwise, we were
		 * returned here due to the lack of exif tags. */
		Options->Result = CORR_NOEXIFINPUT;
		return 0;
	}
	if (IncludesGPS && !Options->OverwriteExisting)
	{
		/* Already have GPS data in the file!
		 * So we can't do this again... */
		Options->Result = CORR_GPSDATAEXISTS;
		return 0;
	}

	/* Now convert the time into Unixtime. */
	time_t PhotoTime =
		ConvertToUnixTime(TimeTemp, EXIF_DATE_FORMAT,
			Options->TimeZoneHours, Options->TimeZoneMins);

	/* Add the PhotoOffset time. This is to make the Photo time match
	 * the GPS time - ie, it is (GPS - Photo). */
	PhotoTime += Options->PhotoOffset;

	/* Free the memory for the time string - it won't otherwise
	 * be freed for us. */
	free(TimeTemp);

	/* Check to see if MinTime and MaxTime are filled in.
	 * If not, fill them in. */
	if (Options->MinTime == 0 && Options->MaxTime == 0)
	{
		/* Alright, fill them in! 
		 * Requires us to go through the list and keeping
		 * the biggest and smallest. The list should,
		 * however, be sorted. But we do it this way anyway. */
		struct GPSPoint* Fill = NULL;
		Options->MinTime = Options->Points->Time;
		for (Fill = Options->Points; Fill; Fill = Fill->Next)
		{
			/* Ignore trackseg markers... */
			if (Fill->Lat == 1000 && Fill->Long == 1000)
				continue;
			/* Check the Min time */
			if (Fill->Time < Options->MinTime)
				Options->MinTime = Fill->Time;
			/* Check the Max time */
			if (Fill->Time > Options->MaxTime) 
				Options->MaxTime = Fill->Time;
		}
	}

	/* Check that the photo is within the times that
	 * our tracks are for. Can't really match it if
	 * we were not logging when it was taken. */
	/* Note: photos taken between logging sessions of the
	 * same file will still make it inside of this. In
	 * some cases, it won't matter, but if it does, then
	 * keep this in mind!! */
	if ((PhotoTime < Options->MinTime) ||
			(PhotoTime > Options->MaxTime))
	{
		/* Outside the range. Abort. */
		Options->Result = CORR_NOMATCH;
		return 0;
	}

	/* Time to run through the list, and see if our PhotoTime
	 * is in between two points. Alternately, it might be
	 * exactly on a point... even better... */
	struct GPSPoint* Search;
	struct GPSPoint* Actual = malloc(sizeof(struct GPSPoint));

	Options->Result = CORR_NOMATCH; /* For convenience later */
	
	for (Search = Options->Points; Search; Search = Search->Next)
	{
		/* Sanity check: we need to peek at the next point.
		 * Make sure we can. */
		if (Search->Next == NULL) break;
		/* Sanity check: does this point have the same
		 * timestamp as the next? If so, skip onward. */
		if (Search->Time == Search->Next->Time) continue;
		/* Sanity check: does this point have a later
		 * timestamp than the next point? If so, skip. */
		if (Search->Time > Search->Next->Time) continue;

		if (Options->DoBetweenTrkSeg)
		{
			/* Righto, we are interpolating between segments.
			 * So simply do nothing! Simple! */
		} else {
			/* Don't check between track segments.
			 * If the end of segment marker is set, then simply
			 * "jump" over this point. */
			if (Search->EndOfSegment)
			{
				continue;
			}
		}

		/* Sanity check / track segment fix: is the photo time before
		 * the current point? If so, we've gone past it. Hrm. */
		if (Search->Time > PhotoTime)
		{
			Options->Result = CORR_NOMATCH;
			break;
		}
		
		/* Sort of sanity check: is this photo inside our
		 * "feather" time? If not, abort. */
		if (Options->FeatherTime)
		{
			/* Is the point between these two? */
			if ((PhotoTime > Search->Time) &&
				(PhotoTime < Search->Next->Time))
			{
				/* It is. Now is it too far
				 * from these two? */
				if (((Search->Time + Options->FeatherTime) < PhotoTime) &&
					((Search->Next->Time - Options->FeatherTime) > PhotoTime))
				{ 
					/* We are inside the feather
					 * time between two points.
					 * Abort. */
					Options->Result = CORR_TOOFAR;
					free(Actual);
					return NULL;
				} 
			}
		} /* endif (Options->Feather) */
		
		/* First test: is it exactly this point? */
		if (PhotoTime == Search->Time)
		{
			/* This is the point, exactly.
			 * Copy out the data and return that. */
			Actual->Lat = Search->Lat;
			Actual->Long = Search->Long;
			Actual->Elev = Search->Elev;
			Actual->Time = Search->Time;

			Options->Result = CORR_OK;
			break;
		}
		
		/* Second test: is it between this and the
		 * next point? */
		if ((PhotoTime > Search->Time) &&
				(PhotoTime < Search->Next->Time))
		{
			/* It is between these points.
			 * Unless told otherwise, we interpolate.
			 * If not interpolating, we round to nearest.
			 * If points are eqidistant, we round down. */
			if (Options->NoInterpolate)
			{
				/* No interpolation. Round. */
				Round(Search, Actual,
						Options, PhotoTime);
				Options->Result = CORR_ROUND;
				break;
			} else {
				/* Interpolate away! */
				Interpolate(Search, Actual,
						Options, PhotoTime);
				Options->Result = CORR_INTERPOLATED;
				break;
			}
		}
	} /* End for() loop to search. */

	/* Did we actually match it at all? */
	if (Options->Result == CORR_NOMATCH)
	{
		/* Nope, no match at all. */
		/* Return with nothing. */
		free(Actual);
		return NULL;
	}

	/* Write the data back into the Exif info. If we're allowed. */
	if (Options->NoWriteExif)
	{
		/* Don't write exif tags. Just return. */
		return Actual;
	} else {
		/* Do write the exif tags. And then return. */
		if (WriteGPSData(Filename, Actual, Options->Datum, Options->NoChangeMtime, Options->DegMinSecs))
		{
			/* All ok. Good! Return. */
			return Actual;
		} else {
			/* Not good. Return point, but note failure. */
			Options->Result = CORR_EXIFWRITEFAIL;
			return Actual;
		}
	}
	
	/* Looks like nothing matched. Free the prepared memory,
	 * and return nothing. */
	free(Actual);
	return NULL;
};

void Round(struct GPSPoint* First, struct GPSPoint* Result,
		struct CorrelateOptions* Options, time_t PhotoTime)
{
	/* Round the point between the two points - ie, it will end
	 * up being one or the other point. */
	struct GPSPoint* CopyFrom = NULL;

	/* Determine the difference between the two points. 
	 * We're using the scale function used by interpolate.
	 * This gives us a good view of where we are... */
	double Scale = (double)First->Next->Time - (double)First->Time;
	Scale = ((double)PhotoTime - (double)First->Time) / Scale;

	/* Compare our scale. */
	if (Scale <= 0.5)
	{
		/* Closer to the first point. */
		CopyFrom = First;
	} else {
		/* Closer to the second point. */
		CopyFrom = First->Next;
	}

	/* Copy the numbers over... */
	Result->Lat = CopyFrom->Lat;
	Result->Long = CopyFrom->Long;
	Result->Elev = CopyFrom->Elev;
	Result->Time = CopyFrom->Time;

	/* Done! */
	
}

void Interpolate(struct GPSPoint* First, struct GPSPoint* Result,
		struct CorrelateOptions* Options, time_t PhotoTime)
{
	/* Interpolate between the two points. The first point
	 * is First, the other First->Next. Results into Result. */

	/* Calculate the "scale": a decimal giving the relative distance
	 * in time between the two points. Ie, a number between 0 and 1 - 
	 * 0 is the first point, 1 is the next point, and 0.5 would be
	 * half way. */
	double Scale = (double)First->Next->Time - (double)First->Time;
	Scale = ((double)PhotoTime - (double)First->Time) / Scale;

	/* Now calculate the Lattitude. */
	Result->Lat = First->Lat + ((First->Next->Lat - First->Lat) * Scale);

	/* And the longitude. */
	Result->Long = First->Long + ((First->Next->Long - First->Long) * Scale);

	/* And the elevation. If elevation wasn't set, it should be zero.
	 * Which works quite fine for us. */
	Result->Elev = First->Elev + ((First->Next->Elev - First->Elev) * Scale);

	/* The time is not interpolated, but matches photo. */
	Result->Time = PhotoTime;

	/* And that should have fixed us... */

}