[Python] QGIS Image Rendering is blurry

In QGIS 3.22 I want to save an extract of an OpenStreetMap layer I included with https://tile.openstreetmap.org/{z}/{x}/{y}.png. There is only one layer.

However, the extract of the layer is sharp in OSM and blurry in the exported image.

I changed various parameters:

• layer porpoerties: tile resolution
• resolution of the exported image
• dpi
• zoom

but the qualitiy of the png is always worse than the quality of the same OSM extract in QGIS.

What am I doing wrong?

Here is the code:

def to3857Coords(lat,lon):
from pyproj import Proj, transform
P3857 = Proj(init='epsg:3857')
P4326 = Proj(init='epsg:4326')
x,y = transform(P4326, P3857, lon, lat)
return x,y


def saveImg(xsize, ysize, dotspermeter):
img = QImage(QSize(xsize, ysize), QImage.Format_ARGB32_Premultiplied)
img.setDotsPerMeterX(dotspermeter)
img.setDotsPerMeterY(dotspermeter)

# create map settings
ms = QgsMapSettings()

# create painter
p = QPainter()
p.begin(img)
p.setRenderHint(QPainter.HighQualityAntialiasing)

# set layers to render
layers = list(reversed([lyr for lyr in QgsProject.instance().mapLayers().values()]))
ms.setLayers(layers)
for lyr in QgsProject.instance().mapLayers().values():
print(lyr)

# set extent
rect = iface.mapCanvas().extent()
print(rect)
#rect.scale(1.1)
ms.setExtent(rect)

# set ouptut size
ms.setOutputSize(img.size())

# setup qgis map renderer
render = QgsMapRendererCustomPainterJob(ms, p)
render.start()
render.waitForFinished()
p.end()

# save image
img.save('/tmp/test_render_'+str(xsize)+'_'+str(ysize)+'_'+str(dotspermeter)+'.png')
print('Done')


#wroclaw

#lat , lon , zoom (1128.5 corresponds to 18) , xsize , ysize , dotspermeter
conf=[
[51.11, 17.032222, 1128.5, 1540, 770, 1],
[51.11, 17.032222, 1128.5, 1540, 770, 10], # dotspermeter increased, no difference(?); I tried many values
[51.11, 17.032222, 1128.5, 15400, 7700, 1],
[51.11, 17.032222, 2257, 3080, 1540, 1],
[51.11, 17.032222, 4514, 6160, 3080, 1],
[51.11, 17.032222, 1128.5*8, 1540*8, 770*8, 1],
[51.11, 17.032222, 1128.5, 1550, 775, 1],
[51.11, 17.032222, 1128.5, 1546, 773, 1],
]
lat , lon , zoom , xsize , ysize , dotspermeter = conf[7]


canvas = iface.mapCanvas()
x, y = to3857Coords(lat, lon)
canvas.setCenter(QgsPointXY(x, y))
canvas.zoomScale(zoom)
saveImg(xsize, ysize, dotspermeter

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