Description
This example shows: how to set a bitmap in a GRIB message to encode missing values in the data
Source code
grib_set_bitmap.f90
! (C) Copyright 2005- ECMWF. ! ! This software is licensed under the terms of the Apache Licence Version 2.0 ! which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. ! ! In applying this licence, ECMWF does not waive the privileges and immunities granted to it by ! virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction. ! ! ! ! Description: how to set a bitmap in a GRIB message ! to encode missing values in the data ! ! program set_bitmap use eccodes implicit none integer :: infile,outfile integer :: igrib, iret integer :: numberOfValues real, dimension(:), allocatable :: values real :: missingValue logical :: grib1Example grib1Example=.true. if (grib1Example) then ! GRIB 1 example call codes_open_file(infile,'../../data/regular_latlon_surface.grib1','r') else ! GRIB 2 example call codes_open_file(infile,'../../data/regular_latlon_surface.grib2','r') end if call codes_open_file(outfile,'out.set_bitmap_f.grib','w') ! A new grib message is loaded from file ! igrib is the grib id to be used in subsequent calls call codes_grib_new_from_file(infile,igrib) ! The missingValue is not coded in the message. ! It is a value we define as a placeholder for a missing value ! at a point in the grid. ! It should be chosen so that it cannot be confused ! with a valid field value missingValue=1.0e36 call codes_set(igrib, 'missingValue',missingValue) write(*,*) 'missingValue=',missingValue ! get the size of the values array call codes_get_size(igrib,'values',numberOfValues) write(*,*) 'numberOfValues=',numberOfValues allocate(values(numberOfValues), stat=iret) ! get data values call codes_get(igrib,'values',values) ! enable bitmap call codes_set(igrib, 'bitmapPresent', 1) ! set some values to be missing values(1:10) = missingValue ! set the values (the bitmap will be automatically built) call codes_set(igrib,'values', values) ! write modified message to a file call codes_write(igrib,outfile) ! free memory call codes_release(igrib) call codes_close_file(infile) call codes_close_file(outfile) deallocate(values) end program set_bitmap
grib_set_bitmap.py
# (C) Copyright 2005- ECMWF. # # This software is licensed under the terms of the Apache Licence Version 2.0 # which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. # # In applying this licence, ECMWF does not waive the privileges and immunities granted to it by # virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction. # # Description: how to set a bitmap in a GRIB message # to encode missing values in the data # import traceback import sys from eccodes import * INPUT = '../../data/regular_latlon_surface.grib1' OUTPUT = 'out.set_bitmap_p.grib' MISSING = 1.0e36 VERBOSE = 1 # verbose error reporting def example(): fin = open(INPUT, 'rb') fout = open(OUTPUT, 'wb') gid = codes_grib_new_from_file(fin) # The missingValue is not coded in the message. # It is a value we define as a placeholder for a missing value # at a point in the grid. # It should be chosen so that it cannot be confused # with a valid field value codes_set(gid, 'missingValue', MISSING) values = codes_get_values(gid) # Enable bitmap codes_set(gid, 'bitmapPresent', 1) # Change some data values to be missing num_missing = 0 for i in range(100): # Set every other value to a missing value if i % 2 == 0: values[i] = MISSING num_missing += 1 codes_set_values(gid, values) # Check counts of missing and non-missing values num_data = codes_get(gid, 'numberOfDataPoints', int) assert num_data == len(values) assert codes_get(gid, 'numberOfCodedValues', int) == num_data - num_missing assert codes_get(gid, 'numberOfMissing', int) == num_missing codes_write(gid, fout) codes_release(gid) fin.close() fout.close() def main(): try: example() except CodesInternalError as err: if VERBOSE: traceback.print_exc(file=sys.stderr) else: print(err.msg, file=sys.stderr) return 1 if __name__ == "__main__": sys.exit(main())
grib_set_bitmap.c
/* * (C) Copyright 2005- ECMWF. * * This software is licensed under the terms of the Apache Licence Version 2.0 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. * * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction. */ /* * C Implementation: grib_set_bitmap * * Description: how to set a bitmap in a GRIB message * to encode missing values in the data * */ #include <stdio.h> #include <stdlib.h> #include "eccodes.h" int main(int argc, char** argv) { int err = 0; size_t size=0; FILE* in = NULL; const char* infile = "../../data/regular_latlon_surface.grib1"; FILE* out = NULL; const char* outfile = "out.set_bitmap_c.grib"; codes_handle *h = NULL; const void* buffer = NULL; size_t values_len; double* values; double missing=1.0e36; int i=0; in = fopen(infile, "r"); if(!in) { printf("ERROR: unable to open input file %s\n",infile); return 1; } out = fopen(outfile, "w"); if(!out) { printf("ERROR: unable to open output file %s\n",outfile); fclose(in); return 1; } h = codes_handle_new_from_file(0, in, PRODUCT_GRIB, &err); if (h == NULL) { printf("Error: unable to create handle from file %s\n",infile); } CODES_CHECK(codes_set_double(h, "missingValue", missing),0); /* get the size of the values array*/ CODES_CHECK(codes_get_size(h, "values", &values_len),0); values = (double*)malloc(values_len*sizeof(double)); /* get data values*/ CODES_CHECK(codes_get_double_array(h, "values", values, &values_len),0); CODES_CHECK(codes_set_long(h, "bitmapPresent", 1),0); for(i = 0; i < 10; i++) { values[i]=missing; } CODES_CHECK(codes_set_double_array(h, "values", values, values_len),0); /* get the coded message in a buffer */ CODES_CHECK(codes_get_message(h, &buffer, &size),0); /* write the buffer in a file*/ if(fwrite(buffer, 1, size, out) != size) { perror(outfile); exit(1); } codes_handle_delete(h); fclose(in); fclose(out); return 0; }