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Diffstat (limited to 'noao/mtlocal/pds/structure.hlp')
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1 files changed, 85 insertions, 0 deletions
diff --git a/noao/mtlocal/pds/structure.hlp b/noao/mtlocal/pds/structure.hlp new file mode 100644 index 00000000..6bb2eab8 --- /dev/null +++ b/noao/mtlocal/pds/structure.hlp @@ -0,0 +1,85 @@ +.help pdsread 2 "Program Structure" +.sh +PDSREAD Structure Chart + +.nf +t_pdsread() +# Returns when file list is satisfied or if EOT is encountered. + + read_pds (pdsfile, iraffile) + # Returns OK or EOF + + read_header (pds_fd, im, parameters) + # Returns OK or EOF + + read_image (pds_fd, im, parameters) + + set_image_header (im) + + init_read_scan (parameters) + # Returns OK + + read_scan (fd, scanbuf) + # Returns EOF or number of points in a scan +.fi + +.sh +PDSREAD Structure Summary + +.ls t_pdsread +The main procedure reads the control parameters. +The files to be read and converted are calculated from the specified source +and file list. +A loop through the files determines the specific input source names and +output file names and calls READ_PDS for each conversion. +.ls read_pds +The input source is opened and the output image header file is created. +If only the PDS header is to be listed then a temporary image header +file is created. The PDS header is read and decoded into the IRAF +image header bye READ_HEADER. If the image is to be read then +READ_IMAGE is called. Finally all files are closed. If a temporary +image file was created it is deleted. +.ls read_header +The 120 byte PDS header is read into an integer array. The ID string +in the first 80 bytes is unpacked into a text string using the MIIUP routine +and stored in the IRAF image header. The 12 bit PDP values are converted to +SPP short data valuese using the routine APDP8S. +The PDP 059 text code is converted to ASCII using the routine APDP059. +The remaining header quantities are unpacked into short +or long SPP integers using the MIIUP, APDP8S, UNPACKS and UNPACKL and +the image dimensions are stored in the IRAF image header. +Finally the PRINT_HEADER is called to print a long or short version of the +header. +.le +.ls read_image +The PDS image pixels are converted to an IRAF image file. +The image file header is set. +The lines of the image are converted one at a time. +.ls set_image_header +The pixel type for the IRAF image is set to the user specified type. +If no type has been specified then the type is determined from the +number of bits per pixel given in pds.h. +.le +.ls init_read_scan +Initializes the scan parameters. Input is a long integer array containing +the decoded header parameters. The procedure uses the number of data points +per scan, the number of records per scan and the number of points per full +records, calculates and allocates the buffer space required and determines +the size of each record in chars. If the tape is an old 7 track tape the +size of the record must be rounded up till it holds an integral number +of Cyber words in length. For example a record containing 1001 real data +points will actually be 1005 data points long with junk in the last 4 spaces. +.le +.ls read_scan +Reads an entire PDS scan a record at a time looping over the number of +records per scan. The procedure uses the MIIUP +routine which is machine dependent. The bitpix must correspond to +an MII type. READ_SCAN returns the number of data points per scan or EOF. +READ_SCAN calls APDP8S to convert the 10 or 12 bit data values to short +integers and calls AFLIPS to flip every other scan if the PDS scan +is a raster scan. +.le +.le +.le +.le +.endhelp |