Skip to content
Permalink
Browse files

[processing]added new example script (contributed by Michael Douchin)

  • Loading branch information
volaya committed Mar 27, 2014
1 parent 7b0af0d commit 7f0bc42ea5c68e2a986abf12278acae6e5b88eea
@@ -0,0 +1,103 @@
##[Example scripts]=group
##Create rasters from canvas for each vector feature extent=name
##vector_layer=vector
##scale=number 250000.0
##dpi=number 96
##image_width_mm=number 0
##image_height_mm=number 0
##output_directory=folder
##outputDir=output string

from qgis.core import *
from qgis.gui import *
from qgis.utils import iface
from PyQt4.QtCore import *
from PyQt4.QtGui import *
import os

# Loop though grid layerfeatures
layer = processing.getObject(vector_layer)
provider = layer.dataProvider()

# Get map renderer
mapRenderer = iface.mapCanvas().mapRenderer()

# Create a new composition
c = QgsComposition(mapRenderer)
c.setPrintResolution(dpi)

# Add a composer map object
x, y = 0, 0
composerMap = QgsComposerMap(c, x, y, image_width_mm, image_height_mm)
c.addComposerMap(composerMap)
composerMap.setBackgroundEnabled(False)

# World file
c.setWorldFileMap(composerMap)
c.setGenerateWorldFile( True )

# Get vector layer features
feats = processing.features(layer)
nFeat = len(feats)
i = 0
progress.setText(u'%s tiles to be generated' % nFeat)

# Iterate over the features
for feat in feats:
# Log progression
progress.setPercentage(int(100 * i / nFeat))
i+=1

# Get the feature bouding box
geom = feat.geometry()
rect = geom.boundingBox()

# Recalculate paper width and heigh if not given
if not image_width_mm and scale > 0:
image_width_mm = rect.width() * 1000 / scale
if not image_height_mm and scale > 0:
image_height_mm = rect.height() * 1000 / scale

# Calculate image size in Pixel
inch2mm = 25.4
image_width_pixel = int(image_width_mm * dpi / inch2mm)
image_height_pixel = int(image_height_mm * dpi / inch2mm)
progress.setText(u'Feature %s - Image width : %s * %s mm / %s * %s pixels' % (
i,
image_width_mm,
image_height_mm,
image_width_pixel,
image_height_pixel
)
)

# Set paper and composerMap width and height
c.setPaperSize(image_width_mm, image_height_mm)
composerMap.setItemPosition(x, y, image_width_mm, image_height_mm)

# Set the map extent and scale
composerMap.setNewExtent(rect)
if scale > 0:
composerMap.setNewScale(scale)

# Image destination path
outputPath= "tile_%s_%s" % (scale, i)
outputImagePath = os.path.join(output_directory, outputPath + '.png')

# Generate image from composition
myImage = c.printPageAsRaster(0)
myImage.save(outputImagePath)

# Generate World file
wf = c.computeWorldFileParameters()
outputWorldPath = os.path.join(output_directory, outputPath + '.pgw')
with open(outputWorldPath, 'w') as f:
f.write('%s\n' % wf[0])
f.write('%s\n' % wf[1])
f.write('%s\n' % wf[3])
f.write('%s\n' % wf[4])
f.write('%s\n' % wf[2])
f.write('%s\n' % wf[5])

# export chosen output directory as a output variable
outputDir = output_directory
@@ -0,0 +1,42 @@
(dp0
S'outputDir'
p1
VThe directory where the rasters will be saved. This output can be used as a parameter for another script or algorithm (for example upcoming gdalbuildvrt )
p2
sS'ALG_DESC'
p3
VBuilding a good looking map often implies to create a QGIS project with many layers : roads, styled dem, contour lines, rivers, etc.\u000aFor large areas, QGIS can suffer to render each layers every time the user pan or zoom in or out. \u000a\u000aThis algorithm allows to create a georeferenced raster which mimics the image rendered by QGIS for all displayed layers. This way you can use the exported raster instead of all the layers as a base layer for your projects.\u000a\u000aThe user chooses the input vector layer, a scale and optionnaly the size of the raster in mm. The script iterate over the vector features. \u000a\u000aFor each feature:\u000a\u000a* the extent of the feature is calculated\u000a* the size of the output raster is calculated in mm "paper size", unless width and height are given\u000a* the canvas is rendered for the feature extent, at the given scale, and the result is saved as a png\u000a* a world file containing the georeferencement parameters is also saved ( *.pgw )
p4
sS'image_height_mm'
p5
V(optionnal) The height in mm of the output raster. If left to 0, the script will calculate it automatically to render the whole feature extent.
p6
sS'ALG_CREATOR'
p7
VMicha�l DOUCHIN ( 3liz.com )
p8
sS'vector_layer'
p9
VThe vector layer containing the features to use to calculate each raster extent. You can use an existing layer, or a layer created with other algorithm (for example a regular grid of 250km by 250km)
p10
sS'output_directory'
p11
VThe directory where the rasters will be saved.
p12
sS'scale'
p13
VThe scale at which the canvas will be rendered
p14
sS'ALG_HELP_CREATOR'
p15
VMicha�l DOUCHIN ( 3liz.com )
p16
sS'image_width_mm'
p17
V(optionnal) The width in mm of the output raster. If left to 0, the script will calculate it automatically to render the whole feature extent.
p18
sS'dpi'
p19
VThe resolution of the output rasters. "dpi" means "dot per inch"
p20
s.

0 comments on commit 7f0bc42

Please sign in to comment.
You can’t perform that action at this time.