QGIS: MapExporter using QPainter()

qgis_MapExporter.py

from qgis.core import QgsProject, QgsMapSettings, QgsRectangle, QgsMapRendererCustomPainterJob
from qgis.PyQt.QtGui import QImage, QPainter
from PyQt5.QtCore import QSize
from pathlib import Path
import time

class MapExporter:
    def __init__(self, canvas):
        self.canvas = canvas
        self.project = QgsProject.instance()

    def calculate_size_from_extent(self, extent, scale, dpi):
        width_meters = extent.width()
        height_meters = extent.height()
        
        width_pixels = int((width_meters * dpi) / (scale * 0.0254))
        height_pixels = int((height_meters * dpi) / (scale * 0.0254))
        
        return width_pixels, height_pixels

    def export_map_to_image(self, output_path, extent, scale=2500, dpi=96, width_px=None, height_px=None):
        if not width_px or not height_px:
            width_px, height_px = self.calculate_size_from_extent(extent, scale, dpi)
        
        map_settings = self.canvas.mapSettings()
        map_settings.setExtent(extent)
        map_settings.setOutputSize(QSize(width_px, height_px))
        map_settings.setOutputDpi(dpi)

        # Use the canvas's current layer set
        map_settings.setLayers(self.canvas.layers())

        image = QImage(width_px, height_px, QImage.Format_ARGB32_Premultiplied)
        image.setDotsPerMeterX(int(dpi / 25.4 * 1000))
        image.setDotsPerMeterY(int(dpi / 25.4 * 1000))

        painter = QPainter(image)
        job = QgsMapRendererCustomPainterJob(map_settings, painter)
        job.start()
        job.waitForFinished()

        image.save(str(output_path), "png")
        painter.end()

    def export_layer_extent(self, output_path, layer_name):
        layer = self.project.mapLayersByName(layer_name)[0]
        extent = layer.extent()
        self.export_map_to_image(output_path, extent)

# Usage example:
canvas = iface.mapCanvas()
exporter = MapExporter(canvas)

# Set filename with Unix timestamp
timestamp = int(time.time())
filename = f"export_{timestamp}.png"
output_path = Path(r'/tmp/') / filename

# Export current canvas extent
exporter.export_map_to_image(output_path, canvas.extent())

# Or export using layer extent
# exporter.export_layer_extent(output_path, "export area")

# Or export using custom extent
# custom_extent = QgsRectangle(243154.6823, 4681314.4688, 243624.3177, 4681714.5313)
# exporter.export_map_to_image(output_path, custom_extent)