1funimageget(3) SAORD Documentation funimageget(3)
2
6 FunImageGet - get an image or image section
7
9 #include <funtools.h>
10 void *FunImageGet(Fun fun, void *buf, char *plist)
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14 The FunImageGet() routine returns an binned image array of the speci‐
15 fied section of a Funtools data file. If the input data are already of
16 type image, the array is generated by extracting the specified image
17 section and then binning it according to the specified bin factor. If
18 the input data are contained in a binary table or raw event file, the
19 rows are binned on the columns specified by the bincols= keyword (using
20 appropriate default columns as necessary), after which the image sec‐
21 tion and bin factors are applied. In both cases, the data is automati‐
22 cally converted from FITS to native format, if necessary.
23 The first argument is the Funtools handle returned by FunOpen(). The
25 second buf argument is a pointer to a data buffer to fill. If NULL is
26 specified, FunImageGet will allocate a buffer of the appropriate size.
27 Generally speaking, you always want Funtools to allocate the buffer
28 because the image dimensions will be determined by Funtools image sec‐
29 tioning on the command line.
30 The third plist (i.e., parameter list) argument is a string containing
32 one or more comma-delimited keyword=value parameters. It can be used
33 to specify the return data type using the bitpix= keyword. If no such
34 keyword is specified in the plist string, the data type of the returned
35 image is the same as the data type of the original input file, or is of
36 type int for FITS binary tables.
37 If the bitpix= keyword is supplied in the plist string, the data type
39 of the returned image will be one of the supported FITS image data
40 types:
41 · 8 unsigned char
43 · 16 short
45 · 32 int
47 · -32 float
49 · -64 double
51 For example:
53 void *buf;
55 /* extract data section into an image buffer */
56 if( !(buf = FunImageGet(fun, NULL, NULL)) )
57 gerror(stderr, "could not FunImageGet: %s\n", iname);
58 will allocate buf and retrieve the image in the file data format. In
60 this case, you will have to determine the data type (using the
61 FUN_SECT_BITPIX value in the FunInfoGet() routine) and then use a
62 switch statement to process each data type:
63 int bitpix;
65 void *buf;
66 unsigned char *cbuf;
67 short *sbuf;
68 int *ibuf;
69 ...
70 buf = FunImageGet(fun, NULL, NULL);
71 FunInfoGet(fun, FUN_SECT_BITPIX, &bitpix, 0);
72 /* set appropriate data type buffer to point to image buffer */
73 switch(bitpix){
74 case 8:
75 cbuf = (unsigned char *)buf; break;
76 case 16:
77 sbuf = (short *)buf; break;
78 case 32:
79 ibuf = (int *)buf; break;
80 ...
81 See the imblank example code for more details on how to process an
83 image when the data type is not specified beforehand.
84 It often is easier to specify the data type directly:
86 double *buf;
88 /* extract data section into a double image buffer */
89 if( !(buf = FunImageGet(fun, NULL, "bitpix=-64")) )
90 gerror(stderr, "could not FunImageGet: %s\n", iname);
91 will extract the image while converting to type double.
93 On success, a pointer to the image buffer is returned. (This will be
95 the same as the second argument, if NULL is not passed to the latter.)
96 On error, NULL is returned.
97 In summary, to retrieve image or row data into a binned image, you sim‐
99 ply call FunOpen() followed by FunImageGet(). Generally, you then will
100 want to call FunInfoGet() to retrieve the axis dimensions (and data
101 type) of the section you are processing (so as to take account of sec‐
102 tioning and blocking of the original data):
103 double *buf;
105 int i, j;
106 int dim1, dim2;
107 ... other declarations, etc.
108 /* open the input FITS file */
110 if( !(fun = FunOpen(argv[1], "rc", NULL)) )
111 gerror(stderr, "could not FunOpen input file: %s\n", argv[1]);
112 /* extract and bin the data section into a double float image buffer */
114 if( !(buf = FunImageGet(fun, NULL, "bitpix=-64")) )
115 gerror(stderr, "could not FunImageGet: %s\n", argv[1]);
116 /* get dimension information from funtools structure */
118 FunInfoGet(fun, FUN_SECT_DIM1, &dim1, FUN_SECT_DIM2, &dim2, 0);
119 /* loop through pixels and reset values below limit to value */
121 for(i=0; i<dim1*dim2; i++){
122 if( buf[i] <= blimit ) buf[i] = bvalue;
123 }
124 Another useful plist string value is "mask=all", which returns an image
126 populated with regions id values. Image pixels within a region will
127 contain the associated region id (region values start at 1), and other‐
128 wise will contain a 0 value. Thus, the returned image is a region mask
129 which can be used to process the image data (which presumably is
130 retrieved by a separate call to FunImageGet) pixel by pixel.
131 If a FITS binary table or a non-FITS raw event file is being binned
133 into an image, it is necessary to specify the two columns that will be
134 used in the 2D binning. This usually is done on the command line using
135 the bincols=(x,y) keyword:
136 funcnts "foo.ev[EVENTS,bincols=(detx,dety)]"
138 The full form of the bincols= specifier is:
140 bincols=([xname[:tlmin[:tlmax:[binsiz]]]],[yname[:tlmin[:tlmax[:binsiz]]]])
142 where the tlmin, tlmax, and binsiz specifiers determine the image bin‐
144 ning dimensions:
145 dim = (tlmax - tlmin)/binsiz (floating point data)
147 dim = (tlmax - tlmin)/binsiz + 1 (integer data)
148 These tlmin, tlmax, and binsiz specifiers can be omitted if TLMIN,
150 TLMAX, and TDBIN header parameters (respectively) are present in the
151 FITS binary table header for the column in question. Note that if only
152 one parameter is specified, it is assumed to be tlmax, and tlmin
153 defaults to 1. If two parameters are specified, they are assumed to be
154 tlmin and tlmax.
155 If bincols is not specified on the command line, Funtools tries to use
157 appropriate defaults: it looks for the environment variable FITS_BIN‐
158 COLS (or FITS_BINKEY). Then it looks for the Chandra parameters CPREF
159 (or PREFX) in the FITS binary table header. Failing this, it looks for
160 columns named "X" and "Y" and if these are not found, it looks for col‐
161 umns containing the characters "X" and "Y".
162 See Binning FITS Binary Tables and Non-FITS Event Files for more infor‐
164 mation.
165
167 See funtools(n) for a list of Funtools help pages
168version 1.4.0 August 15, 2007 funimageget(3)