[QGIS-Developer] How to create QgsRasterLayer from gdal "MEM" dataset

[zhang liye]

Hi, All

I try to visualize the numpy.array matrix 'm' as a raster layer from Qgis.  Because I have to show the matrix dynamically, I  do not want to save the raster to *.tif file.
Is there any way to do this.   I can create raster dataset using gdal library, but do not know how to create a raster layer to show on Qgis window.  The code is as follows.  Thank you so much!

def show_matrix_as_raster(self, m, lng_min, lat_min, pixelWidth, pixelHeight):
    cols = m.shape[1]
    rows = m.shape[0]

    driver = gdal.GetDriverByName('MEM')
    outRaster = driver.Create('', cols, rows, 1, gdal.GDT_Byte)   # create dataset in memory
    outRaster.SetGeoTransform((lng_min, pixelWidth, 0, lat_min, 0, pixelHeight))
   outband = outRaster.GetRasterBand(1)
    outband.WriteArray(m)
    outRasterSRS = osr.SpatialReference()
    outRasterSRS.ImportFromEPSG(4326)
    outRaster.SetProjection(outRasterSRS.ExportToWkt())
    outband.FlushCache()

   layer = QgsRasterLayer( file_name_???, layer_name)    # how to create QgsRsterLayer from 'outRaster', rather than file?
   QgsMapLayerRegistry.instance().addMapLayer( layer )

    ###### render
    ##
    myGrayRenderer = QgsSingleBandGrayRenderer(layer.dataProvider(), 1)
    layer.setRenderer(myGrayRenderer)
    renderer = layer.renderer()
    uses_band = renderer.usesBands()

    myType = renderer.dataType(uses_band[0])
    myEnhancement = QgsContrastEnhancement(myType)
    contrast_enhancement = QgsContrastEnhancement.StretchToMinimumMaximum
    myEnhancement.setContrastEnhancementAlgorithm(contrast_enhancement, True)

    myEnhancement.setMinimumValue(m.min())
    myEnhancement.setMaximumValue(m.max())

    layer.renderer().setContrastEnhancement(myEnhancement)
    layer.renderer().setOpacity(0.5)
    layer.triggerRepaint()

    if layer.isValid() is False:
        print "Unable to show the raster layer."


Best regards!
Liye,

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