import os
from osgeo import gdal, ogr, osr
import tempfile
from polsartools.utils.utils import time_it
[docs]
@time_it
def clip(folder_path, output_folder=None,
start_x=None, start_y=None, dx=None, dy=None,
north=None, south=None, east=None, west=None,
vector_path=None, outType='tif', auto_reference=True):
"""
Subsets PolSAR matrix rasters (e.g., C3, C2, T3) from a given folder using spatial or pixel-based criteria.
This function processes all raster files in the input folder and clips them based on one of three methods:
- Pixel-based window (`start_x`, `start_y`, `dx`, `dy`)
- Geographic bounding box (`north`, `south`, `east`, `west`)
- Vector file mask (`vector_path`)
The clipped rasters are saved to the specified output folder in either GeoTIFF (.tif) or ENVI binary (.bin) format.
Examples
--------
>>> clip("input_path", "out_path", start_x=100, start_y=200, dx=512, dy=512)
>>> clip("input_path", "out_path", north=45.0, south=44.5, east=-66.0, west=-67.0)
>>> clip("input_path", "out_path", vector_path="clip_mask.shp", outType='bin')
Parameters
----------
folder_path : str
Path to the input folder containing PolSAR matrix rasters (e.g., C3, C2, T3).
output_folder : str
Path to the folder where clipped rasters will be saved. Defaults to a subfolder named "clip" in the input folder.
start_x : int, optional
Starting pixel index along the x-axis (column) for pixel-based clipping.
start_y : int, optional
Starting pixel index along the y-axis (row) for pixel-based clipping.
dx : int, optional
Width of the pixel window to clip.
dy : int, optional
Height of the pixel window to clip.
north : float, optional
Northern latitude boundary for geographic clipping.
south : float, optional
Southern latitude boundary for geographic clipping.
east : float, optional
Eastern longitude boundary for geographic clipping.
west : float, optional
Western longitude boundary for geographic clipping.
vector_path : str, optional
Path to a vector file (e.g., shapefile or GeoJSON) used for spatial masking.
outType : str, optional
Output format: 'tif' for GeoTIFF or 'bin' for ENVI binary. Defaults to 'tif'.
auto_reference : bool, optional
If True, automatically infers georeferencing from input rasters. Defaults to True.
Returns
-------
None
The function saves clipped raster files to the specified output folder.
Notes
-----
- Only one clipping method should be used per call: pixel window, geographic bbox, or vector mask.
- All rasters in the input folder are processed and clipped uniformly.
- ENVI binary output includes accompanying `.hdr` header files.
"""
if output_folder is None:
output_folder = os.path.join(os.path.dirname(folder_path), "clip")
if not os.path.exists(output_folder):
os.makedirs(output_folder)
# Validate clipping mode
pixel_params = all(v is not None for v in [start_x, start_y, dx, dy])
geo_params = all(v is not None for v in [north, south, east, west])
vector_param = vector_path is not None
mode_count = sum([pixel_params, geo_params, vector_param])
if mode_count != 1:
print("Error: Please provide only one clipping method: pixel-based, geo-based (NSEW), or vector file.")
return
raster_exts = ['.tif', '.bin']
shape_counter = {}
shape_map = {}
#collect shapes
for filename in os.listdir(folder_path):
if not any(filename.lower().endswith(ext) for ext in raster_exts):
continue
input_path = os.path.join(folder_path, filename)
dataset = gdal.Open(input_path)
if not dataset:
continue
shape = (dataset.RasterXSize, dataset.RasterYSize)
shape_map[filename] = shape
shape_counter[shape] = shape_counter.get(shape, 0) + 1
if not shape_counter:
print("No valid raster files found.")
return
ref_shape = max(shape_counter.items(), key=lambda x: x[1])[0]
# process matching rasters
for filename in os.listdir(folder_path):
if not any(filename.lower().endswith(ext) for ext in raster_exts):
continue
if shape_map.get(filename) != ref_shape:
print(f"Skipping {filename}: shape mismatch.")
continue
input_path = os.path.join(folder_path, filename)
dataset = gdal.Open(input_path)
if not dataset:
print(f"Failed to open {filename}")
continue
geotransform = dataset.GetGeoTransform()
projection = dataset.GetProjection()
output_path = os.path.join(output_folder, f"{os.path.splitext(filename)[0]}.{outType}")
if vector_path:
# Vector-based clipping
vector_ds = ogr.Open(vector_path)
layer = vector_ds.GetLayer()
vector_srs = layer.GetSpatialRef()
raster_srs = osr.SpatialReference()
raster_srs.ImportFromWkt(projection)
if not raster_srs.IsSame(vector_srs):
print(f"Reprojecting vector to match raster CRS for {filename}...")
# Create temporary GeoJSON file
temp_vector_path = os.path.join(
tempfile.gettempdir(),
f"reprojected_{os.path.splitext(os.path.basename(vector_path))[0]}.geojson"
)
driver = ogr.GetDriverByName("GeoJSON")
if os.path.exists(temp_vector_path):
os.remove(temp_vector_path)
reproj_ds = driver.CreateDataSource(temp_vector_path)
reproj_layer = reproj_ds.CreateLayer("reprojected", srs=raster_srs, geom_type=layer.GetGeomType())
coord_transform = osr.CoordinateTransformation(vector_srs, raster_srs)
layer_defn = layer.GetLayerDefn()
for i in range(layer_defn.GetFieldCount()):
field_defn = layer_defn.GetFieldDefn(i)
reproj_layer.CreateField(field_defn)
for feature in layer:
geom = feature.GetGeometryRef()
geom.Transform(coord_transform)
new_feature = ogr.Feature(reproj_layer.GetLayerDefn())
new_feature.SetGeometry(geom)
for i in range(layer_defn.GetFieldCount()):
new_feature.SetField(layer_defn.GetFieldDefn(i).GetNameRef(), feature.GetField(i))
reproj_layer.CreateFeature(new_feature)
new_feature = None
vector_ds = None
layer = None
vector_path = temp_vector_path # Use reprojected GeoJSON
warp_options = gdal.WarpOptions(
format='GTiff' if outType == 'tif' else 'ENVI',
cutlineDSName=vector_path,
cropToCutline=True,
dstNodata=0,
options=['COMPRESS=DEFLATE', 'PREDICTOR=2', 'ZLEVEL=9', 'TILED=YES'] if outType == 'tif' else None
)
gdal.Warp(output_path, dataset, options=warp_options)
print(f"Saved file {output_path}")
continue
# Pixel-based or geo-based clipping
if pixel_params:
xoff, yoff = start_x, start_y
xsize, ysize = dx, dy
elif geo_params:
origin_x, pixel_width, _, origin_y, _, pixel_height = geotransform
xoff = int((west - origin_x) / pixel_width)
yoff = int((north - origin_y) / pixel_height)
xsize = int((east - west) / pixel_width)
ysize = int((south - north) / pixel_height)
else:
print(f"Skipping {filename}: insufficient clipping parameters.")
continue
clipped = dataset.ReadAsArray(xoff, yoff, xsize, ysize)
driver = gdal.GetDriverByName('ENVI' if outType == 'bin' else 'GTiff')
out_ds = driver.Create(output_path, xsize, ysize, dataset.RasterCount,
dataset.GetRasterBand(1).DataType,
options=['COMPRESS=DEFLATE', 'PREDICTOR=2', 'ZLEVEL=9', 'TILED=YES'] if outType == 'tif' else None)
for i in range(dataset.RasterCount):
out_ds.GetRasterBand(i + 1).WriteArray(clipped[i] if dataset.RasterCount > 1 else clipped)
new_gt = (
geotransform[0] + xoff * geotransform[1],
geotransform[1],
geotransform[2],
geotransform[3] + yoff * geotransform[5],
geotransform[4],
geotransform[5]
)
out_ds.SetGeoTransform(new_gt)
out_ds.SetProjection(projection)
out_ds.FlushCache()
print(f"Saved file {output_path}")
