patch to add more informative error messages to gdal_crs.c

[schuyler@…]

The crs.c code actually has more informative error indications than was being thrown via CPLError(). This patch gives the developer slightly more clue as to where things went wrong.

diff -Naur gdal-1.3.2/alg/gdal_crs.c gdal-1.3.2-new/alg/gdal_crs.c
--- gdal-1.3.2/alg/gdal_crs.c   2004-12-26 11:12:21.000000000 -0500
+++ gdal-1.3.2-new/alg/gdal_crs.c       2006-12-12 16:23:38.000000000 -0500
@@ -101,6 +101,13 @@
 void *GDALDeserializeGCPTransformer( CPLXMLNode *psTree );
 CPL_C_END

+static char *CRS_error_message[] = {
+    "Failed to compute GCP transform: Not enough points available",
+    "Failed to compute GCP transform: Transform is not solvable",
+    "Failed to compute GCP transform: Not enough memory"
+    "Failed to compute GCP transform: Parameter error",
+    "Failed to compute GCP transform: Internal error"
+};
 /* crs.c */
 static int CRS_georef(double, double, double *, double *,
                               double [], double [], int);
@@ -217,14 +224,13 @@
 /* -------------------------------------------------------------------- */
 /*      Compute the forward and reverse polynomials.                    */
 /* -------------------------------------------------------------------- */
-    if( CRS_compute_georef_equations( &sPoints,
+    int nCRSresult = CRS_compute_georef_equations( &sPoints,
                                       psInfo->adfToGeoX, psInfo->adfToGeoY,
                                       psInfo->adfFromGeoX, psInfo->adfFromGeoY,
-                                      nReqOrder ) != 1 )
+                                      nReqOrder );
+    if (nCRSresult != 1 )
     {
-        CPLError( CE_Failure, CPLE_AppDefined,
-                  "Failed to compute polynomial equations of desired order\n"
-                  "for provided control points." );
+        CPLError( CE_Failure, CPLE_AppDefined, CRS_error_message[-nCRSresult] );
         goto CleanupAfterError;
     }

[warmerdam]

Swapnil,

Could you apply this patch, and find some way to test it?  I think the
easiest way would be to create an image with 3 colinear GCPs and then use
gdalwarp to warp it.  You should get the message about "Transform is not
solvable". 

GCPs can be added to an image with gdal_translate and the -gcp option. 

[hobu]

Swapnil,

I applied the patch, with some minor modification to make sure it works on windows.

Howard

[rouault]

Fixed since quite some time!