Modifying and updating QGIS renderer XML configurations
This tutorial demonstrates how to change the rendering of different single symbol renderers from within qgisremote:
Vector renderers
Polygon rendering
Get some polygon data
borders <- raster::getData("GADM", country = "LUX", level = 2)
# start with blank project
library(qgisremote)
iface.newProject()## NULL# add data
l <- iface.addVectorLayer(borders)
# get default renderer
r <- mapLayer.renderer(l)
# inspect renderer
as.character(r)## [1] "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<!DOCTYPE xml>\n<renderer-v2 forceraster=\"0\" symbollevels=\"0\" type=\"singleSymbol\" enableorderby=\"0\">\n <symbols>\n <symbol alpha=\"1\" clip_to_extent=\"1\" type=\"fill\" name=\"0\">\n <layer pass=\"0\" class=\"SimpleFill\" locked=\"0\">\n <prop k=\"border_width_map_unit_scale\" v=\"0,0,0,0,0,0\"/>\n <prop k=\"color\" v=\"181,121,72,255\"/>\n <prop k=\"joinstyle\" v=\"bevel\"/>\n <prop k=\"offset\" v=\"0,0\"/>\n <prop k=\"offset_map_unit_scale\" v=\"0,0,0,0,0,0\"/>\n <prop k=\"offset_unit\" v=\"MM\"/>\n <prop k=\"outline_color\" v=\"0,0,0,255\"/>\n <prop k=\"outline_style\" v=\"solid\"/>\n <prop k=\"outline_width\" v=\"0.26\"/>\n <prop k=\"outline_width_unit\" v=\"MM\"/>\n <prop k=\"style\" v=\"solid\"/>\n </layer>\n </symbol>\n </symbols>\n <rotation/>\n <sizescale scalemethod=\"diameter\"/>\n</renderer-v2>\n"qgisxml(r)## name attrname value
## 1 renderer-v2 forceraster 0
## 2 renderer-v2 symbollevels 0
## 3 renderer-v2 type singleSymbol
## 4 renderer-v2 enableorderby 0
## 5 symbol alpha 1
## 6 symbol clip_to_extent 1
## 7 symbol type fill
## 8 symbol name 0
## 9 layer pass 0
## 10 layer class SimpleFill
## 11 layer locked 0
## 12 layer border_width_map_unit_scale 0,0,0,0,0,0
## 13 layer color 181,121,72,255
## 14 layer joinstyle bevel
## 15 layer offset 0,0
## 16 layer offset_map_unit_scale 0,0,0,0,0,0
## 17 layer offset_unit MM
## 18 layer outline_color 0,0,0,255
## 19 layer outline_style solid
## 20 layer outline_width 0.26
## 21 layer outline_width_unit MM
## 22 layer style solid
## 23 sizescale scalemethod diameterSet fill transparent with dashed blue outline:
qgisxml(r, 'layer', 'color') <- '0,0,0,0'
qgisxml(r, 'layer', 'outline_color') <- 'blue'
qgisxml(r, 'layer', 'outline_style') <- 'dash'
qgisxml(r, 'layer', 'outline_width') <- 0.3
# add offset to where lines are drawn
qgisxml(r, 'offset')## [1] "0,0"qgisxml(r, 'offset') <- '1,2'
mapLayer.renderer(l) <- r
raster::plotRGB(mapCanvas.saveAsImage())
Simply switching a polygon layer over to the line symbol type does not work, since the line renderer will simply fail to show polygon data on the canvas.
Line rendering
Want to style polygons using a line renderer only? Add the data as a line layer:
borders <- as(borders, 'SpatialLines')
l <- iface.addVectorLayer(borders, 'borderlines')
r <- mapLayer.renderer(l)
qgisxml(r)## name attrname value
## 1 renderer-v2 forceraster 0
## 2 renderer-v2 symbollevels 0
## 3 renderer-v2 type singleSymbol
## 4 renderer-v2 enableorderby 0
## 5 symbol alpha 1
## 6 symbol clip_to_extent 1
## 7 symbol type line
## 8 symbol name 0
## 9 layer pass 0
## 10 layer class SimpleLine
## 11 layer locked 0
## 12 layer capstyle square
## 13 layer customdash 5;2
## 14 layer customdash_map_unit_scale 0,0,0,0,0,0
## 15 layer customdash_unit MM
## 16 layer draw_inside_polygon 0
## 17 layer joinstyle bevel
## 18 layer line_color 70,235,10,255
## 19 layer line_style solid
## 20 layer line_width 0.26
## 21 layer line_width_unit MM
## 22 layer offset 0
## 23 layer offset_map_unit_scale 0,0,0,0,0,0
## 24 layer offset_unit MM
## 25 layer use_custom_dash 0
## 26 layer width_map_unit_scale 0,0,0,0,0,0
## 27 sizescale scalemethod diameter# compare the offset and non-offset borders
raster::plotRGB(mapCanvas.saveAsImage())
Point (symbol) rendering
l <- iface.addVectorLayer('https://d2ad6b4ur7yvpq.cloudfront.net/naturalearth-3.3.0/ne_50m_populated_places.geojson')
r <- mapLayer.renderer(l)
as.character(r)## [1] "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<!DOCTYPE xml>\n<renderer-v2 forceraster=\"0\" symbollevels=\"0\" type=\"singleSymbol\" enableorderby=\"0\">\n <symbols>\n <symbol alpha=\"1\" clip_to_extent=\"1\" type=\"marker\" name=\"0\">\n <layer pass=\"0\" class=\"SimpleMarker\" locked=\"0\">\n <prop k=\"angle\" v=\"0\"/>\n <prop k=\"color\" v=\"181,91,137,255\"/>\n <prop k=\"horizontal_anchor_point\" v=\"1\"/>\n <prop k=\"joinstyle\" v=\"bevel\"/>\n <prop k=\"name\" v=\"circle\"/>\n <prop k=\"offset\" v=\"0,0\"/>\n <prop k=\"offset_map_unit_scale\" v=\"0,0,0,0,0,0\"/>\n <prop k=\"offset_unit\" v=\"MM\"/>\n <prop k=\"outline_color\" v=\"0,0,0,255\"/>\n <prop k=\"outline_style\" v=\"solid\"/>\n <prop k=\"outline_width\" v=\"0\"/>\n <prop k=\"outline_width_map_unit_scale\" v=\"0,0,0,0,0,0\"/>\n <prop k=\"outline_width_unit\" v=\"MM\"/>\n <prop k=\"scale_method\" v=\"diameter\"/>\n <prop k=\"size\" v=\"2\"/>\n <prop k=\"size_map_unit_scale\" v=\"0,0,0,0,0,0\"/>\n <prop k=\"size_unit\" v=\"MM\"/>\n <prop k=\"vertical_anchor_point\" v=\"1\"/>\n </layer>\n </symbol>\n </symbols>\n <rotation/>\n <sizescale scalemethod=\"diameter\"/>\n</renderer-v2>\n"qgisxml(r)## name attrname value
## 1 renderer-v2 forceraster 0
## 2 renderer-v2 symbollevels 0
## 3 renderer-v2 type singleSymbol
## 4 renderer-v2 enableorderby 0
## 5 symbol alpha 1
## 6 symbol clip_to_extent 1
## 7 symbol type marker
## 8 symbol name 0
## 9 layer pass 0
## 10 layer class SimpleMarker
## 11 layer locked 0
## 12 layer angle 0
## 13 layer color 181,91,137,255
## 14 layer horizontal_anchor_point 1
## 15 layer joinstyle bevel
## 16 layer name circle
## 17 layer offset 0,0
## 18 layer offset_map_unit_scale 0,0,0,0,0,0
## 19 layer offset_unit MM
## 20 layer outline_color 0,0,0,255
## 21 layer outline_style solid
## 22 layer outline_width 0
## 23 layer outline_width_map_unit_scale 0,0,0,0,0,0
## 24 layer outline_width_unit MM
## 25 layer scale_method diameter
## 26 layer size 2
## 27 layer size_map_unit_scale 0,0,0,0,0,0
## 28 layer size_unit MM
## 29 layer vertical_anchor_point 1
## 30 sizescale scalemethod diameterChange the marker type and colour:
qgisxml(r, 'layer', 'name') <- 'triangle'
qgisxml(r, 'color') <- 'blue'
mapLayer.renderer(l) <- r
mapCanvas.zoomOut()## [1] 522106.9raster::plotRGB(mapCanvas.saveAsImage())
Raster renderers
Get some SRTM elevation data and add it to QGIS.
elevation <- raster::getData("alt", country = "DNK")
iface.newProject()## NULLl <- iface.addRasterLayer(elevation)
mapCanvas.zoomToFullExtent()## [1] 1875079r <- mapLayer.renderer(l)
as.character(r)## [1] "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<!DOCTYPE xml>\n<QgsSingleBandGrayRenderer>\n <rasterrenderer gradient=\"BlackToWhite\" opacity=\"1\" alphaBand=\"-1\" type=\"singlebandgray\" grayBand=\"1\">\n <rasterTransparency/>\n <contrastEnhancement>\n <minValue>-0.988</minValue>\n <maxValue>92.866</maxValue>\n <algorithm>StretchToMinimumMaximum</algorithm>\n </contrastEnhancement>\n </rasterrenderer>\n</QgsSingleBandGrayRenderer>\n"qgisxml(r)## name attrname value
## 1 rasterrenderer gradient BlackToWhite
## 2 rasterrenderer opacity 1
## 3 rasterrenderer alphaBand -1
## 4 rasterrenderer type singlebandgray
## 5 rasterrenderer grayBand 1Tile layers
Tile layers might be different in how their data is retrieved, but they are otherwise simply raster layers which are displayed using a singlebandcolordata renderer.
l <- iface.addTileLayer('http://c.tile.openstreetmap.org/{z}/{x}/{y}.png')
qgisxml(mapLayer.renderer(l))## name attrname value
## 1 rasterrenderer opacity 1
## 2 rasterrenderer alphaBand -1
## 3 rasterrenderer band 1
## 4 rasterrenderer type singlebandcolordataTheir display can primarily be changed by adjusting lower-level options in their corresponding style:
## name attrname value
## 1 rasterrenderer opacity 1
## 2 rasterrenderer alphaBand -1
## 3 rasterrenderer band 1
## 4 rasterrenderer type singlebandcolordata
## 5 brightnesscontrast brightness 0
## 6 brightnesscontrast contrast 0
## 7 huesaturation colorizeGreen 128
## 8 huesaturation colorizeOn 0
## 9 huesaturation colorizeRed 255
## 10 huesaturation colorizeBlue 128
## 11 huesaturation grayscaleMode 0
## 12 huesaturation saturation 0
## 13 huesaturation colorizeStrength 100
## 14 rasterresampler maxOversampling 2