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raw2tiff: avoid divide by 0

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fixes #151 / http://bugzilla.maptools.org/show_bug.cgi?id=2839

first memcmp() lines before computing corellation
and always avoid divide by 0 anyway
This commit is contained in:
Thomas Bernard 2020-02-08 11:47:38 +01:00
parent b4820b2179
commit bdcf1add10
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GPG Key ID: 0FF11B67A5C0863C
1 changed files with 18 additions and 7 deletions
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25
tools/raw2tiff.c
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@ -372,7 +372,7 @@ guessSize(int fd, TIFFDataType dtype, _TIFF_off_t hdr_size, uint32 nbands,
_TIFF_stat_s filestat;
uint32 w, h, scanlinesize, imagesize;
uint32 depth = TIFFDataWidth(dtype);
float cor_coef = 0, tmp;
double cor_coef = 0, tmp;
if (_TIFF_fstat_f(fd, &filestat) == -1) {
fprintf(stderr, "Failed to obtain file size.\n");
@ -419,22 +419,28 @@ guessSize(int fd, TIFFDataType dtype, _TIFF_off_t hdr_size, uint32 nbands,
w++) {
if (imagesize % w == 0) {
scanlinesize = w * depth;
h = imagesize / w;
if (h < 2)
continue;
/* reads 2 lines at the middle of the image and calculate their correlation.
* it works for h >= 2. (in this case it will compare line 0 and line 1 */
buf1 = _TIFFmalloc(scanlinesize);
buf2 = _TIFFmalloc(scanlinesize);
h = imagesize / w;
do {
if (_TIFF_lseek_f(fd, hdr_size + (int)(h/2)*scanlinesize,
if (_TIFF_lseek_f(fd, hdr_size + (int)((h - 1)/2)*scanlinesize,
SEEK_SET) == (_TIFF_off_t)-1) {
fprintf(stderr, "seek error.\n");
fail=1;
break;
}
/* read line (h-1)/2 */
if (read(fd, buf1, scanlinesize) !=
(long) scanlinesize) {
fprintf(stderr, "read error.\n");
fail=1;
break;
}
/* read line ((h-1)/2)+1 */
if (read(fd, buf2, scanlinesize) !=
(long) scanlinesize) {
fprintf(stderr, "read error.\n");
@ -445,11 +451,15 @@ guessSize(int fd, TIFFDataType dtype, _TIFF_off_t hdr_size, uint32 nbands,
swapBytesInScanline(buf1, w, dtype);
swapBytesInScanline(buf2, w, dtype);
}
tmp = (float) fabs(correlation(buf1, buf2,
w, dtype));
if (tmp > cor_coef) {
cor_coef = tmp;
if (0 == memcmp(buf1, buf2, scanlinesize)) {
*width = w, *length = h;
} else {
tmp = fabs(correlation(buf1, buf2,
w, dtype));
if (tmp > cor_coef) {
cor_coef = tmp;
*width = w, *length = h;
}
}
} while (0);
@ -564,6 +574,7 @@ correlation(void *buf1, void *buf2, uint32 n_elem, TIFFDataType dtype)
M2 /= n_elem;
D1 -= M1 * M1 * n_elem;
D2 -= M2 * M2 * n_elem;
if (D1 * D2 == 0.0) return 0.0; /* avoid divide by zero */
K = (K - M1 * M2 * n_elem) / sqrt(D1 * D2);
return K;