| 1 | subroutine pngunpack(cpack,len,idrstmpl,ndpts,fld) |
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| 2 | !$$$ SUBPROGRAM DOCUMENTATION BLOCK |
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| 3 | ! . . . . |
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| 4 | ! SUBPROGRAM: pngunpack |
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| 5 | ! PRGMMR: Gilbert ORG: W/NP11 DATE: 2000-06-21 |
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| 6 | ! |
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| 7 | ! ABSTRACT: This subroutine unpacks a data field that was packed into a |
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| 8 | ! PNG image format |
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| 9 | ! using info from the GRIB2 Data Representation Template 5.41 or 5.40010. |
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| 10 | ! |
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| 11 | ! PROGRAM HISTORY LOG: |
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| 12 | ! 2000-06-21 Gilbert |
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| 13 | ! |
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| 14 | ! USAGE: CALL pngunpack(cpack,len,idrstmpl,ndpts,fld) |
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| 15 | ! INPUT ARGUMENT LIST: |
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| 16 | ! cpack - The packed data field (character*1 array) |
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| 17 | ! len - length of packed field cpack(). |
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| 18 | ! idrstmpl - Contains the array of values for Data Representation |
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| 19 | ! Template 5.41 or 5.40010 |
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| 20 | ! ndpts - The number of data values to unpack |
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| 21 | ! |
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| 22 | ! OUTPUT ARGUMENT LIST: |
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| 23 | ! fld() - Contains the unpacked data values |
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| 24 | ! |
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| 25 | ! REMARKS: None |
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| 26 | ! |
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| 27 | ! ATTRIBUTES: |
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| 28 | ! LANGUAGE: XL Fortran 90 |
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| 29 | ! MACHINE: IBM SP |
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| 30 | ! |
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| 31 | !$$$ |
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| 32 | |
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| 33 | character(len=1),intent(in) :: cpack(len) |
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| 34 | integer,intent(in) :: ndpts,len |
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| 35 | integer,intent(in) :: idrstmpl(*) |
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| 36 | real,intent(out) :: fld(ndpts) |
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| 37 | |
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| 38 | integer :: ifld(ndpts) |
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| 39 | character(len=1),allocatable :: ctemp(:) |
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| 40 | integer(4) :: ieee |
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| 41 | real :: ref,bscale,dscale |
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| 42 | integer :: dec_png,width,height |
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| 43 | |
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| 44 | ieee = idrstmpl(1) |
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| 45 | call rdieee(ieee,ref,1) |
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| 46 | bscale = 2.0**real(idrstmpl(2)) |
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| 47 | dscale = 10.0**real(-idrstmpl(3)) |
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| 48 | nbits = idrstmpl(4) |
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| 49 | itype = idrstmpl(5) |
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| 50 | ! |
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| 51 | ! if nbits equals 0, we have a constant field where the reference value |
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| 52 | ! is the data value at each gridpoint |
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| 53 | ! |
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| 54 | if (nbits.ne.0) then |
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| 55 | allocate(ctemp(ndpts*4)) |
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| 56 | iret=dec_png(cpack,width,height,ctemp) |
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| 57 | call g2lib_gbytes(ctemp,ifld,0,nbits,0,ndpts) |
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| 58 | deallocate(ctemp) |
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| 59 | do j=1,ndpts |
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| 60 | fld(j)=((real(ifld(j))*bscale)+ref)*dscale |
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| 61 | enddo |
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| 62 | else |
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| 63 | do j=1,ndpts |
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| 64 | fld(j)=ref |
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| 65 | enddo |
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| 66 | endif |
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| 67 | |
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| 68 | |
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| 69 | return |
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| 70 | end |
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