qgis-21-qgisprocess-cli-headless

name	qgis-21-qgisprocess-cli-headless
description	Sub-skill of qgis: 2.1 qgis_process CLI (Headless) (+2).
version	1.0.0
category	engineering/gis
type	reference
scripts_exempt	true

2.1 qgis_process CLI (Headless) (+2)

2.1 qgis_process CLI (Headless)

# List available algorithms
qgis_process list

# Run an algorithm
qgis_process run native:buffer \
  --INPUT=/data/wells.gpkg \
  --DISTANCE=5000 \
  --SEGMENTS=36 \
  --OUTPUT=/data/wells_5km_buffer.gpkg

# Run with JSON params file
qgis_process run native:reprojectlayer \
  --parameters=reproject_params.json

2.2 Python Processing Framework

import processing
from qgis.core import QgsVectorLayer

# Reproject wells to UTM Zone 31N (offshore NW Europe)
result = processing.run("native:reprojectlayer", {
    "INPUT":      layer,
    "TARGET_CRS": QgsCoordinateReferenceSystem("EPSG:32631"),
    "OUTPUT":     "memory:"
})
utm_layer = result["OUTPUT"]

# Buffer: 500 m radius around each well
result = processing.run("native:buffer", {
    "INPUT":    utm_layer,
    "DISTANCE": 500,
    "SEGMENTS": 32,
    "OUTPUT":   "/data/well_exclusion_zones.gpkg"
})

2.3 Common Processing Algorithms

Algorithm	ID	Use
Reproject	native:reprojectlayer	CRS transform
Buffer	native:buffer	Proximity zones
Spatial join	native:joinattributesbylocation	Overlay
Clip	native:clip	Mask to AOI
Merge layers	native:mergevectorlayers	Combine datasets
Raster clip	gdal:cliprasterbymasklayer	Crop bathymetry
Contour	gdal:contour	Depth contours

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