Switch sand and wetland patterns to SVG

landcover.mss

@@ -616,7 +616,7 @@
 
 #landcover-area-symbols {
   [int_wetland != null][zoom >= 10] {
-    polygon-pattern-file: url('symbols/wetland.png');
+    polygon-pattern-file: url('symbols/wetland.svg');
     polygon-pattern-alignment: global;
   }
   [natural = 'reef'][zoom >= 10] {
@@ -651,7 +651,7 @@
     [natural = 'beach'],
     [natural = 'shoal'] {
       [surface = 'sand'] {
-        polygon-pattern-file: url('symbols/beach.png');
+        polygon-pattern-file: url('symbols/beach.svg');
         polygon-pattern-alignment: global;
       }
       [surface = 'gravel'],

symbols/generating_patterns/beach.md

@@ -1,11 +1,9 @@
+Pattern file for beach is generated in two steps.
 
-The beach and reef patterns are rasterized and colored versions of the provided SVGs
+In the first step visit [jsdotpattern (command sequence is recorded)](http://www.imagico.de/map/jsdotpattern.php#x,128,jdp59980;g,2.25,16,16;rx,250,2,8,8;rx,250,2,8,8;s,jdp58799;s,jdp49103;rx,250,2,8,8;rd,0,0,1,scree,0.1,5,10,0,jdp31724,dbb677,fff1ba;)
 
-```
-convert -depth 8 beach.svg beach_raw.png
-convert -depth 8 reef.svg reef_raw.png
+Use "get pattern SVG data" (it is expected that background will be transparent, background colour in jsdotpattern is only for display).
 
-convert -depth 8 -size 128x128 xc:"#685d45" \( beach_raw.png -negate \) -set colorspace RGB -alpha Off -compose CopyOpacity -composite -set colorspace sRGB +gamma - beach.png
-convert -depth 8 -size 256x256 xc:"#969696" \( reef_raw.png -negate \) -set colorspace RGB -alpha Off -compose CopyOpacity -composite -set colorspace sRGB +gamma - beach_coarse.png
-convert -depth 8 -size 256x256 xc:"#549ccd" \( reef_raw.png -negate \) -set colorspace RGB -alpha Off -compose CopyOpacity -composite -set colorspace sRGB +gamma - reef.png
-```
+Generated SVG image is sanitized for use with Mapnik by the script svg_pattern.sh from the jsdotpattern repository at http://github.com/imagico/jsdotpattern.
+
+The final file is beach.svg

symbols/generating_patterns/reef.md

@@ -0,0 +1,9 @@
+
+The reef patterns are rasterized and colored versions of the provided SVG
+
+```
+convert -depth 8 reef.svg reef_raw.png
+
+convert -depth 8 -size 256x256 xc:"#969696" \( reef_raw.png -negate \) -set colorspace RGB -alpha Off -compose CopyOpacity -composite -set colorspace sRGB +gamma - beach_coarse.png
+convert -depth 8 -size 256x256 xc:"#549ccd" \( reef_raw.png -negate \) -set colorspace RGB -alpha Off -compose CopyOpacity -composite -set colorspace sRGB +gamma - reef.png
+```