A basic 2-dimensional Frame is used to represent the pixel coordinate system in the returned Polygon.
The Domain attribute is set to
" , the Title attribute is set to
" Pixel coordinates
" , and the Unit
attribute for each axis is set to
" . All other attributes are left unset. The nature of the pixel
coordinate system is determined by parameter STARPIX.
You should use a function which matches the numerical type of the data you are processing by replacing
in the generic function name AST_CONVEXX
are procesing data with type REAL, you should use the function AST_CONVEXR (see the
" Data Type
" section below for the codes appropriate to other numerical types).
AST__LT: include pixels with value less than VALUE.
AST__LE: include pixels with value less than or equal to VALUE.
AST__EQ: include pixels with value equal to VALUE.
AST__NE: include pixels with value not equal to VALUE.
AST__GE: include pixels with value greater than or equal to VALUE.
AST__GT: include pixels with value greater than VALUE.
The storage order of data within this array should be such that the index of the first grid dimension varies most rapidly and that of the second dimension least rapidly (i.e. normal Fortran array storage order).
Note that LBND and UBND together define the shape and size of
the input grid, its extent along a particular (J
’ th) dimension being
They also define the input grid
’ s coordinate system, each pixel having unit extent along each
dimension with integral coordinate values at its centre or upper corner, as selected by parameter
AST__NULL will be returned if this function is invoked with the global error status set, or if it should fail for any reason.
D: DOUBLE PRECISION
UI: INTEGER (treated as unsigned)
S: INTEGER2 (short integer)
US: INTEGER2 (short integer, treated as unsigned)
B: BYTE (treated as signed)
UB: BYTE (treated as unsigned)
For example, AST_CONVEXD would be used to process DOUBLE PRECISION data, while AST_CONVEXS would be used to process short integer data (stored in an INTEGER2 array), etc.
For compatibility with other Starlink facilities, the codes W and UW are provided as synonyms for S and US respectively (but only in the Fortran interface to AST).
"interface for this function should be used. This alternative interface uses 8 byte integer arguments (instead of 4-byte) to hold pixel indices and pixel counts. Specifically, the arguments LBND and UBND are changed from type INTEGER to type INTEGER8. The function name is changed by inserting the digit
"before the trailing data type code. Thus, AST_CONVEXX becomes AST_CONVEX8X.