1 files changed, 61 insertions, 0 deletions
diff --git a/doc/twcs.c b/doc/twcs.c
new file mode 100644
index 0000000..2da9319
--- /dev/null
+++ b/doc/twcs.c
@@ -0,0 +1,61 @@
+/*
+ *
+ * twcs.c -- example using WCS Library
+ *
+ */
+
+#include <funtools.h>
+
+int main(int argc, char **argv)
+{
+  int i;
+  Fun fun;
+  struct WorldCoor *wcs;  /* WCS info */
+  double x,y,ra,dec,xr,yr;
+
+  if(argc == 1){
+    fprintf(stderr, "usage: twcs iname\n");
+    exit(1);
+  }
+
+  /* open Funtools file */
+  /* Funopen makes initial WCS library call: wcs = wcsinit(header_string) */
+  if( !(fun = FunOpen(argv[1], "r ", NULL)) ){
+    fprintf(stderr, "ERROR can't open file: %s\n", argv[1]);
+    exit(1);
+  }
+
+  /* get wcs structure */
+  FunInfoGet(fun,FUN_WCS,&wcs,0);
+  if( !wcs || !iswcs(wcs) ){
+    fprintf(stderr,"No WCS data");
+    return(1);
+  }
+
+  /* read input, convert pixels to wcs and back */
+  while(1){
+    fprintf(stdout,"\nInput x y: ");
+    if(scanf("%lf %lf", &x, &y) != EOF){
+      if(x <= -999)
+	break;
+      /* convert image pixels to sky coords */
+      pix2wcs(wcs, x, y, &ra, &dec);
+      fprintf(stdout,"Convert from pixels to ra,dec using pix2wcs()\n");
+      fprintf(stdout, "x=%.10g y=%.10g -> ra=%.10g dec=%.10g\n",
+	      x, y, ra, dec);
+      /* convert sky coords to image pixels */
+      fprintf(stdout,"Convert from ra,dec -> pixels using wcs2pix()\n");
+      wcs2pix(wcs, ra, dec, &xr, &yr, &i);
+      fprintf(stdout, "ra=%.10g dec=%.10g -> x=%.10g y=%.10g offscale=%d\n",
+	      ra, dec, xr, yr, i);
+    }
+    else
+      break;
+  }
+
+  /* clean up */
+  /* FunClose makes final WCS library call: wcsfree(wcs) */
+  FunClose(fun);
+  return(0);
+}
+