Wetland patterns are built from two separately generated pattern files by means of raster processing. The basic principle is shown by the following ImageMagick commands:
convert -density 720 pattern.svg -morphology Erode Disk:5.3 \( +clone -fill black -draw 'color 0,0 floodfill' -negate \) +swap -morphology Erode Disk:10.3 -compose Darken -composite -scale 12.5% -depth 8 pattern_casing.png
convert -depth 8 -density 90 wetland.svg wetland_tile.png
montage wetland_tile.png wetland_tile.png wetland_tile.png wetland_tile.png -geometry 256x256+0+0 wetland_512.png
convert wetland_512.png \( pattern_casing.png -negate \) -compose Lighten -composite -threshold 50% \( +clone -negate -morphology hitandmiss peaks:1.9 \) -compose Lighten -composite +level 20%,100% wetland_pattern_bkg.png
convert -depth 8 -size 512x512 xc:"$SYMBOL" \( pattern.png -negate \) -set colorspace RGB -alpha Off -compose CopyOpacity -composite pattern_col.png
convert -depth 8 -size 512x512 xc:"$WETLAND" \( wetland_pattern_bkg.png -negate \) -set colorspace RGB -alpha Off -compose CopyOpacity -composite +compose pattern_col.png -compose Over -composite wetland_pattern.png
In some cases, which has not been elucidated (#3051), the SVG conversions produce files with erroneous sizes. In this case, the following command sequence may work, by using Inkscape to rasterize the SVGs:
inkscape -z --export-png=swamp.png --export-dpi=96 --export-background=white swamp.svg
inkscape -z --export-png=swamp_hr.png --export-dpi=768 --export-background=white swamp.svg
convert swamp_hr.png -morphology Erode Disk:5.3 \( +clone -fill black -draw 'color 0,0 floodfill' -negate \) +swap -morphology Erode Disk:10.3 -compose Darken -composite -scale 12.5% -depth 8 pattern_casing.png
inkscape -z --export-png=wetland_tile.png --export-dpi=96 --export-background=white wetland.svg
montage wetland_tile.png wetland_tile.png wetland_tile.png wetland_tile.png -geometry 256x256+0+0 wetland_512.png
convert wetland_512.png \( pattern_casing.png -negate \) -compose Lighten -composite -threshold 50% \( +clone -negate -morphology hitandmiss peaks:1.9 \) -compose Lighten -composite +level 20%,100% wetland_pattern_bkg.png
convert -depth 8 -size 512x512 xc:"#93b685" \( swamp.png -negate \) -set colorspace RGB -alpha Off -compose CopyOpacity -composite pattern_col.png
convert -depth 8 -size 512x512 xc:"#4aa5fa" \( wetland_pattern_bkg.png -negate \) -set colorspace RGB -alpha Off -compose CopyOpacity -composite +compose pattern_col.png -compose Over -composite +gamma - -strip wetland_pattern.png