diff options
| -rw-r--r-- | converter/other/fitstopnm.c | 13 | ||||
| -rw-r--r-- | converter/other/pamtofits.c | 14 |
2 files changed, 27 insertions, 0 deletions
diff --git a/converter/other/fitstopnm.c b/converter/other/fitstopnm.c index 86bdfbb8..9df47be3 100644 --- a/converter/other/fitstopnm.c +++ b/converter/other/fitstopnm.c @@ -30,6 +30,12 @@ ** disabled min max scanning when reading from stdin. */ +/* + The official specification of FITS format (which is for more than + just visual images) is at + ftp://legacy.gsfc.nasa.gov/fits_info/fits_office/fits_standard.pdf +*/ + #include <string.h> #include <float.h> @@ -507,6 +513,13 @@ convertPgmRaster(FILE * const ifP, double const datamin, xel ** const xels) { + /* Note: the FITS specification does not give the association between + file position and image position (i.e. is the first pixel in the + file the top left, bottom left, etc.). We use the common sense, + popular order of row major, top to bottom, left to right. This + has been the case and accepted since 1989, but in 2008, we discovered + that Gimp and ImageMagick do bottom to top. + */ unsigned int image; pm_message("writing PGM file"); diff --git a/converter/other/pamtofits.c b/converter/other/pamtofits.c index 04b43c35..7a71ff56 100644 --- a/converter/other/pamtofits.c +++ b/converter/other/pamtofits.c @@ -20,6 +20,12 @@ ** in the FITS header, but do not cause the data to be rescaled. */ +/* + The official specification of FITS format (which is for more than + just visual images) is at + ftp://legacy.gsfc.nasa.gov/fits_info/fits_office/fits_standard.pdf +*/ + #include <assert.h> #include <string.h> #include <stdio.h> @@ -201,6 +207,14 @@ writeRaster(struct pam * const pamP, unsigned int const bitpix, int const offset) { + /* Note: the FITS specification does not give the association between + file position and image position (i.e. is the first pixel in the + file the top left, bottom left, etc.). We use the common sense, + popular order of row major, top to bottom, left to right. This + has been the case and accepted since 1989, but in 2008, we discovered + that Gimp and ImageMagick do bottom to top. + */ + unsigned int plane; for (plane = 0; plane < pamP->depth; ++plane) { |