QGIS » QGIS Application

A raster layer file is loaded in QGIS. Then the contents of the file are changed on the filesystem. Forced redraw is applied but QGIS does not draw the correct data. Also, zoom in/zoom out draws different raster data on each zoom level of the same file contents.

I guess there is some deep caching, which is not cleaned. However, I was unable to find a way to empty the cache, even though there was a way in QGIS 2.

This script can be used to reproduce the bug:

import gdal, ogr, os, osr
import numpy as np

filename = 'test2.tif'

if not 'GLOBAL_COUNTER' in globals():
    GLOBAL_COUNTER = 0

def array2raster(filename, rasterOrigin, pixelWidth, pixelHeight, array):
    cols = array.shape[1]
    rows = array.shape[0]
    originX = rasterOrigin[0]
    originY = rasterOrigin[1]
    driver = gdal.GetDriverByName('GTiff')
    outRaster = driver.Create(filename, cols, rows, 1, gdal.GDT_Byte)
    outRaster.SetGeoTransform((originX, pixelWidth, 0, originY, 0, pixelHeight))
    outband = outRaster.GetRasterBand(1)
    outband.WriteArray(array)
    outRasterSRS = osr.SpatialReference()
    outRasterSRS.ImportFromEPSG(4326)
    outRaster.SetProjection(outRasterSRS.ExportToWkt())
    outband.FlushCache()

def generateLayer(filename):
    rasterOrigin = (0, 0)
    pixelWidth = 100
    pixelHeight = 100

    array = np.full((10, 10), 1)

    idx = GLOBAL_COUNTER % 10

    array[idx][idx] = 2

    print(idx, array[idx])

    array2raster(filename, rasterOrigin, pixelWidth, pixelHeight, array)

def layerRefresh(raster):
    raster.dataProvider().reloadData()
    raster.triggerRepaint()
    iface.mapCanvas().refresh()
    iface.layerTreeView().refreshLayerSymbology(raster.id())

generateLayer(filename)

if len(QgsProject.instance().mapLayersByName("testRasterLayer")) == 0:
    iface.addRasterLayer(filename, "testRasterLayer")

QgsProject.instance().reloadAllLayers()
layerRefresh(QgsProject.instance().mapLayersByName("testRasterLayer")[0])

GLOBAL_COUNTER += 1

There is an issue thread on StackExchange too:
https://gis.stackexchange.com/questions/300930/redrawing-raster-layer-after-file-changed-in-qgis