1

I have hundreds of layers. I'd like to be able export each one as a PNG. I can do this by selecting one, and going to project, export map to image, calculate from layer -> select layer -> save. Is there any way I can export all of them as seperate PNG files as a batch process?

I have made progress with the python code below. Unfortunately they are all just white 5k png files.

# create image
img = QImage(QSize(800, 800), QImage.Format_ARGB32_Premultiplied)

# set background color
color = QColor(255, 255, 255, 255)
img.fill(color.rgba())

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

# create map settings
ms = QgsMapSettings()
ms.setBackgroundColor(color)

# set layers to render
#layer = QgsProject.instance().mapLayersByName('stream_order')
#ms.setLayers([layer[0]])


#get all map layers:

layers = QgsProject.instance().mapLayers().values()

#loop through layers

for layer in layers:

    # set extent
    rect = QgsRectangle(ms.fullExtent())
    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 the image
    img.save("C:/imageexport/"+layer.name()+".png")

    print('image saved')

replacing rect = QgsRectangle(ms.fullExtent()) with rect = QgsRectangle(layer.extent()) seemed like the logical solution if the issue was the extent being too big, but this just causes QGIS to crash instantly.

I tried the following code and just got a completely black image.

#image_location = os.path.join(QgsProject.instance().homePath(), "render.png")

vlayer = iface.activeLayer()
#vlayer = QgsProject.instance().mapLayersByName("id_")[0]
options = QgsMapSettings()
options.setLayers([vlayer])
options.setBackgroundColor(QColor(255, 255, 255))
options.setOutputSize(QSize(2000, 2000))
options.setExtent(vlayer.extent())

render = QgsMapRendererParallelJob(options)

def finished():
    img = render.renderedImage()
    img.save("C:/Users/smallfing.FINGBIAL/Documents/SHEFFIELD/Road PNG Export/render.png","png")
    #img.save(image_location, "png")
    print("saved")

render.finished.connect(finished)

render.start()
  • 1
    To do an automation task this I think you should use PyQGIS. – PolyGeo Sep 2 '19 at 21:35
  • Perhaps this answer might help. – Joseph Sep 3 '19 at 13:08
  • Thank you for the suggestion. I have tried with some python code (above) but these all come out as blank. – James Sep 3 '19 at 19:36
0

Try substituting:

render = QgsMapRendererCustomPainterJob(ms, p) 

for:

render = QgsMapRendererParallelJob(ms)
| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.