def custom_stretch(the_raster_layer, values, canvas, mono = False):
"""
Applies a contrast between min and max. If given min and max are 0, then calculates the min and max from gdal.
"""
# logger.info("#######################")
logger.info("custom stretch: values")
logger.info(values)
# print "custom stretch"
# print canvas
# print "layer :", the_raster_layer
# type of layer : raster, vector, other
type_of_layer = the_raster_layer.type()
# take the layer renderer to get the min and max
layer_renderer = the_raster_layer.renderer() # for qgis > 1.9
data_provider = the_raster_layer.dataProvider()
# print "values", values
# the layer has to be a raster layer
if type_of_layer == 1:
if (the_raster_layer.rasterType() == 0 or mono) and layer_renderer:
min_layer, max_layer = values[0]
# gray band
# layer_renderer <qgis.core.QgsSingleBandGrayRenderer object at 0x514caf0>
gray_enhancement = QgsContrastEnhancement(data_provider.dataType(1))
# take the contrast enhancement of the layer threw the renderer
if gray_enhancement:
gray_enhancement.setContrastEnhancementAlgorithm(1) # qgis 1.9
gray_enhancement.setMinimumValue(min_layer)
gray_enhancement.setMaximumValue(max_layer)
layer_renderer.setContrastEnhancement(gray_enhancement)
elif the_raster_layer.rasterType() == 2 and layer_renderer:
# print "layer 3 bandes"
min_red, max_red = values[0]
min_green, max_green = values[1]
min_blue, max_blue = values[2]
logger.debug("red : " + str(min_red) + " " + str(max_red))
logger.debug("green : " + str(min_green) + " " + str(max_green))
logger.debug("blue : " + str(min_blue) + " " + str(max_blue))
red_enhancement = QgsContrastEnhancement(data_provider.dataType(1))
green_enhancement = QgsContrastEnhancement(data_provider.dataType(2))
blue_enhancement = QgsContrastEnhancement(data_provider.dataType(3))
logger.debug("red_enhancement : " + str(red_enhancement))
logger.debug("green_enhancement : " + str(green_enhancement))
logger.debug("blue_enhancement : " + str(blue_enhancement))
# set stretch to min max
red_enhancement.setMinimumValue(min_red)
red_enhancement.setMaximumValue(max_red)
green_enhancement.setMinimumValue(min_green)
green_enhancement.setMaximumValue(max_green)
blue_enhancement.setMinimumValue(min_blue)
blue_enhancement.setMaximumValue(max_blue)
logger.debug("red (1): " + str(red_enhancement.minimumValue()) + " " + str(red_enhancement.maximumValue()))
logger.debug("green (1): " + str(green_enhancement.minimumValue()) + " " + str(green_enhancement.maximumValue()))
logger.debug("blue (1): " + str(blue_enhancement.minimumValue()) + " " + str(blue_enhancement.maximumValue()))
red_enhancement.setContrastEnhancementAlgorithm(1)
green_enhancement.setContrastEnhancementAlgorithm(1)
blue_enhancement.setContrastEnhancementAlgorithm(1)
logger.debug("red (2): " + str(red_enhancement.minimumValue()) + " " + str(red_enhancement.maximumValue()))
logger.debug("green (2): " + str(green_enhancement.minimumValue()) + " " + str(green_enhancement.maximumValue()))
logger.debug("blue (2): " + str(blue_enhancement.minimumValue()) + " " + str(blue_enhancement.maximumValue()))
# print "blue enhancement", blue_enhancement
# print "blue max", blue_enhancement.maximumValue()
# print "blue min", blue_enhancement.minimumValue()
layer_renderer.setRedContrastEnhancement(red_enhancement) # , QgsRaster.ContrastEnhancementCumulativeCut )
layer_renderer.setGreenContrastEnhancement(green_enhancement) # , QgsRaster.ContrastEnhancementCumulativeCut )
layer_renderer.setBlueContrastEnhancement(blue_enhancement) # , QgsRaster.ContrastEnhancementCumulativeCut )
# print "layer renderer"
red_enhancement_debug = layer_renderer.redContrastEnhancement()
green_enhancement_debug = layer_renderer.greenContrastEnhancement()
blue_enhancement_debug = layer_renderer.blueContrastEnhancement()
logger.debug("red (3): " + str(red_enhancement_debug.minimumValue()) + " " + str(red_enhancement_debug.maximumValue()))
logger.debug("green (3): " + str(green_enhancement_debug.minimumValue()) + " " + str(green_enhancement_debug.maximumValue()))
logger.debug("blue (3): " + str(blue_enhancement_debug.minimumValue()) + " " + str(blue_enhancement_debug.maximumValue()))
# print "end"
the_raster_layer.setCacheImage(None)
the_raster_layer.triggerRepaint()
# print "2"
canvas.refresh()
canvas.repaint()
