implement shortcutting proj.4 for 4326->3857 transforms

configure

@@ -639,6 +639,7 @@ PHP_REGEX_INC
 PHP_VERSION_FLAG
 PHPCONFIG
 DEBUG_FLAGS
+PROJ_FASTPATH_ENABLED
 USE_NINT
 USE_POINT_Z_M
 IGNORE_MISSING_DATA
@@ -898,6 +899,7 @@ enable_ignore_missing_data
 enable_point_z_m
 with_warnings
 enable_debug
+enable_proj_fastpath
 enable_cgi_cl_debug_args
 enable_gcov
 with_php
@@ -1550,6 +1552,8 @@ Optional Features:
   --disable-fast-nint     Use safe MS_NINT with reliable rounding
   --enable-debug          Include "-g" in CFLAGS for debugging.
   --disable-debug         Do not include "-g" in CFLAGS (the default).
+  --enable-proj-fastpath  bypass proj.4 for epsg:4326 to epsg:3857
+                          reprojections
   --enable-cgi-cl-debug-args
                           Enable mapserv CGI command-line debug arguments
                           (disabled by default). These command-line args may
@@ -21972,6 +21976,21 @@ else
   CFLAGS=`echo "$CFLAGS -DNDEBUG " | sed "s/-g //"`
 fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to enable proj shortcuts..." >&5
+$as_echo "$as_me: checking whether to enable proj shortcuts..." >&6;}
+# Check whether --enable-proj-fastpath was given.
+if test "${enable_proj_fastpath+set}" = set; then :
+  enableval=$enable_proj_fastpath;
+fi
+
+
+if test "$enable_proj_fastpath" = "yes" ; then
+   PROJ_FASTPATH_ENABLED="-DUSE_PROJ_FASTPATHS"
+   ALL_ENABLED="$PROJ_FASTPATH_ENABLED $ALL_ENABLED"
+fi
+PROJ_FASTPATH_ENABLED=$PROJ_FASTPATH_ENABLED
+
+
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether we should enable mapserv CGI command-line debug arguments..." >&5
 $as_echo "$as_me: checking whether we should enable mapserv CGI command-line debug arguments..." >&6;}
@@ -25153,6 +25172,8 @@ $as_echo "" >&6; }
 $as_echo " -------------- Support Libraries --------- " >&6; }
 { $as_echo "$as_me:${as_lineno-$LINENO}: result:   Proj.4 support:            ${PROJ_ENABLED}" >&5
 $as_echo "  Proj.4 support:            ${PROJ_ENABLED}" >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result:   Proj Fastpaths:            ${PROJ_FASTPATH_ENABLED}" >&5
+$as_echo "  Proj Fastpaths:            ${PROJ_FASTPATH_ENABLED}" >&6; }
 { $as_echo "$as_me:${as_lineno-$LINENO}: result:   Libxml2 support:           ${XML2_ENABLED}" >&5
 $as_echo "  Libxml2 support:           ${XML2_ENABLED}" >&6; }
 { $as_echo "$as_me:${as_lineno-$LINENO}: result:   FriBidi support:           ${FRIBIDI_ENABLED}" >&5

configure.in

@@ -2529,6 +2529,16 @@ else
   CFLAGS=`echo "$CFLAGS -DNDEBUG " | sed "s/-g //"`
 fi
 
+AC_CHECKING(whether to enable proj shortcuts)
+AC_ARG_ENABLE(proj-fastpath,
+     AC_HELP_STRING([--enable-proj-fastpath], [bypass proj.4 for epsg:4326 to epsg:3857 reprojections]),,) 
+
+if test "$enable_proj_fastpath" = "yes" ; then
+   PROJ_FASTPATH_ENABLED="-DUSE_PROJ_FASTPATHS"
+   ALL_ENABLED="$PROJ_FASTPATH_ENABLED $ALL_ENABLED"
+fi
+AC_SUBST(PROJ_FASTPATH_ENABLED,$PROJ_FASTPATH_ENABLED)
+
 dnl ---------------------------------------------------------------------
 dnl Check --enable-cgi-cl-debug-args option (OFF by default)
 dnl ---------------------------------------------------------------------
@@ -2836,6 +2846,7 @@ AC_MSG_RESULT()
 
 AC_MSG_RESULT([ -------------- Support Libraries --------- ])
 AC_MSG_RESULT([  Proj.4 support:            ${PROJ_ENABLED}])
+AC_MSG_RESULT([  Proj Fastpaths:            ${PROJ_FASTPATH_ENABLED}])
 AC_MSG_RESULT([  Libxml2 support:           ${XML2_ENABLED}])
 AC_MSG_RESULT([  FriBidi support:           ${FRIBIDI_ENABLED}])
 AC_MSG_RESULT([  Curl support:              ${CURL_ENABLED}])

mapcopy.c

@@ -72,6 +72,7 @@ int msCopyProjection(projectionObj *dst, projectionObj *src) {
 
     }
 #endif
+    MS_COPYSTELEM(wellknownprojection);
     return MS_SUCCESS;
 }
 

mapfile.c

@@ -1308,7 +1308,17 @@ int msLoadProjectionStringEPSG(projectionObj *p, const char *value)
 #ifdef USE_PROJ
    if(p) msFreeProjection(p);
 
+#ifdef USE_FASTPATH_PROJS
     p->gt.need_geotransform = MS_FALSE;
+    if(strcasestr(value,"epsg:4326")) {
+       p->wellknownprojection = wkp_lonlat;
+    } else if(strcasestr(value,"epsg:3857")) {
+       p->wellknownprojection = wkp_gmerc;
+    } else {
+       p->wellknownprojection = wkp_none;
+    }
+#endif
+
 
     if (strncasecmp(value, "EPSG:", 5) == 0)
     {

mapproject.c

@@ -292,6 +292,30 @@ msProjectShapeLine(projectionObj *in, projectionObj *out,
     int line_alloc = numpoints_in;
     int wrap_test;
 
+#ifdef USE_PROJ_FASTPATHS
+#define MAXEXTENT 20037508.34
+#define M_PIby360 .0087266462599716479
+#define MAXEXTENTby180 111319.4907777777777777777
+ if(in->wellknownprojection == wkp_lonlat && out->wellknownprojection == wkp_gmerc) {
+       for( i = line->numpoints-1; i >= 0; i-- ) {
+#define p_x line->point[i].x
+#define p_y line->point[i].y
+          p_x *= MAXEXTENTby180;
+          p_y = log(tan((90 + p_y) * M_PIby360)) * MS_RAD_TO_DEG;
+          p_y *= MAXEXTENTby180;
+          if (p_x > MAXEXTENT) p_x = MAXEXTENT;
+          if (p_x < -MAXEXTENT) p_x = -MAXEXTENT;
+          if (p_y > MAXEXTENT) p_y = MAXEXTENT;
+          if (p_y < -MAXEXTENT) p_y = -MAXEXTENT;
+#undef p_x
+#undef p_y
+       }
+       return MS_SUCCESS;
+    }
+#endif
+
+
+
     wrap_test = out != NULL && out->proj != NULL && pj_is_latlong(out->proj)
         && !pj_is_latlong(in->proj);
 
@@ -473,6 +497,30 @@ int msProjectShape(projectionObj *in, projectionObj *out, shapeObj *shape)
 {
 #ifdef USE_PROJ
   int i;
+#ifdef USE_PROJ_FASTPATHS
+  int j;
+
+  if(in->wellknownprojection == wkp_lonlat && out->wellknownprojection == wkp_gmerc) {
+     for( i = shape->numlines-1; i >= 0; i-- ) {
+        for( j = shape->line[i].numpoints-1; j >= 0; j-- ) {
+#define p_x shape->line[i].point[j].x
+#define p_y shape->line[i].point[j].y
+           p_x *= MAXEXTENTby180;
+           p_y = log(tan((90 + p_y) * M_PIby360)) * MS_RAD_TO_DEG;
+           p_y *= MAXEXTENTby180;
+           if (p_x > MAXEXTENT) p_x = MAXEXTENT;
+           if (p_x < -MAXEXTENT) p_x = -MAXEXTENT;
+           if (p_y > MAXEXTENT) p_y = MAXEXTENT;
+           if (p_y < -MAXEXTENT) p_y = -MAXEXTENT;
+#undef p_x
+#undef p_y
+        }
+     }
+     return MS_SUCCESS;
+  }
+#endif
+
+
 
   for( i = shape->numlines-1; i >= 0; i-- )
   {

mapproject.h

@@ -41,6 +41,10 @@ extern "C" {
 #  include <proj_api.h>
 #endif
 
+#define wkp_none 0
+#define wkp_lonlat 1
+#define wkp_gmerc 2
+
 
 typedef struct {
 #ifdef SWIG
@@ -63,6 +67,7 @@ typedef struct {
 #endif
   geotransformObj gt; /* extra transformation to apply */
 #endif
+  int wellknownprojection;
 } projectionObj;
 
 #ifndef SWIG