/*============================================================================= st4topgm =============================================================================== Convert an SBIG ST-4 image (not to be confused with the more sophisticated SBIG format that every other SBIG camera produces) to PGM. By Bryan Henderson January 2015. Contributed to the public domain by its author. This program was intended to substitute for the program of the same name in the Debian version of Netpbm, by Justin Pryzby in December 2003. =============================================================================*/ #include #include "pm_config.h" #include "pm_c_util.h" #include "pm.h" #include "pam.h" static unsigned int const st4Height = 165; static unsigned int const st4Width = 192; static unsigned int const st4Maxval = 255; static void validateFileSize(FILE * const ifP) { /*---------------------------------------------------------------------------- Abort program if *ifP is not the proper size for an ST-4 SBIG file. Don't change file position. -----------------------------------------------------------------------------*/ pm_filepos const st4FileSize = (st4Height+1) * st4Width; pm_filepos oldFilePos; pm_filepos endFilePos; pm_tell2(ifP, &oldFilePos, sizeof(endFilePos)); fseek(ifP, 0, SEEK_END); pm_tell2(ifP, &endFilePos, sizeof(endFilePos)); pm_seek2(ifP, &oldFilePos, sizeof(oldFilePos)); if (endFilePos != st4FileSize) pm_error("File is the wrong size for an ST-4 SBIG file. " "It is %u bytes; it should be %u bytes", (unsigned)endFilePos, (unsigned)st4FileSize); } static void writeRaster(FILE * const ifP, struct pam * const pamP) { tuple * tuplerow; unsigned int row; tuplerow = pnm_allocpamrow(pamP); for (row = 0; row < st4Height; ++row) { unsigned int col; for (col = 0; col < st4Width; ++col) { char c; pm_readchar(ifP, &c); tuplerow[col][0] = (unsigned char)c; } pnm_writepamrow(pamP, tuplerow); } pnm_freepamrow(tuplerow); } struct St4Footer { /*---------------------------------------------------------------------------- The information in an ST-4 SBIG footer. -----------------------------------------------------------------------------*/ /* Note that numerical information is in decimal text, because we're lazy. */ char comment[78+1]; char exposureTime[10+1]; char focalLength[10+1]; char apertureArea[10+1]; char calibrationFactor[10+1]; }; static void stripTrailing(char * const arg) { if (strlen(arg) > 0) { char * p; for (p = arg + strlen(arg); p > arg && *(p-1) == ' '; --p); *p = '\0'; } } static void stripLeading(char * const arg) { const char * p; for (p = &arg[0]; *p == ' '; ++p); if (p > arg) memmove(arg, p, strlen(p) + 1); } static void readFooter(FILE * const ifP, struct St4Footer * const footerP) { /*---------------------------------------------------------------------------- Read the footer of the ST-4 image from *ifP, assuming *ifP is positioned to the footer. Return its contents as *footerP. -----------------------------------------------------------------------------*/ char buffer[192]; size_t bytesReadCt; /* The footer is laid out as follows. off len description --- --- ----------- 000 1 Signature: 'v' 001 78 Freeform comment 079 10 Exposure time in 1/100s of a second 089 10 Focal length in inches 099 10 Aperture area in square inches 109 10 Calibration factor 119 73 Reserved Note that the footer is the same length as a raster row. */ bytesReadCt = fread(buffer, 1, sizeof(buffer), ifP); if (bytesReadCt != 192) pm_error("Failed to read footer of image"); if (buffer[0] != 'v') pm_error("Input is not an ST-4 file. We know because the " "signature byte (first byte of the footer) is not 'v'"); buffer[191] = '\0'; memmove(footerP->comment, &buffer[1], 78); footerP->comment[78] = '\0'; stripTrailing(footerP->comment); memmove(footerP->exposureTime, &buffer[79], 10); footerP->exposureTime[10] = '\0'; stripLeading(footerP->exposureTime); memmove(footerP->focalLength, &buffer[89], 10); footerP->focalLength[10] = '\0'; stripLeading(footerP->focalLength); memmove(footerP->apertureArea, &buffer[99], 10); footerP->apertureArea[10] = '\0'; stripLeading(footerP->apertureArea); memmove(footerP->calibrationFactor, &buffer[109], 10); footerP->calibrationFactor[10] = '\0'; stripLeading(footerP->calibrationFactor); } static void reportFooter(struct St4Footer const footer) { pm_message("Comment: %s", footer.comment); pm_message("Exposure time (1/100 s): %s", footer.exposureTime); pm_message("Focal length (in): %s", footer.focalLength); pm_message("Aperture area (sq in): %s", footer.apertureArea); pm_message("Calibration factor: %s", footer.calibrationFactor); } int main(int argc, const char **argv) { FILE * ifP; const char * inputFileName; struct pam outpam; struct St4Footer footer; pm_proginit(&argc, argv); if (argc-1 < 1) inputFileName = "-"; else { inputFileName = argv[1]; if (argc-1 > 1) pm_error("Too many arguments: %u. " "The only possible argument is the " "optional input file name", argc-1); } /* We check the file size to catch the common problem of the input not being valid ST-4 SBIG input. Unlike most formats, this one does not have any signature at the head of the file. More checks on the validity of the format happens when we process the image footer. */ ifP = pm_openr_seekable(inputFileName); validateFileSize(ifP); outpam.size = sizeof(outpam); outpam.len = PAM_STRUCT_SIZE(maxval); outpam.file = stdout; outpam.format = PGM_FORMAT; outpam.plainformat = false; outpam.height = st4Height; outpam.width = st4Width; outpam.depth = 1; outpam.maxval = st4Maxval; pnm_writepaminit(&outpam); writeRaster(ifP, &outpam); readFooter(ifP, &footer); reportFooter(footer); pm_close(ifP); pm_close(stdout); return 0; }