Saya telah menemukan solusi berbasis gdal dan numpy. Ini memecah matriks raster menjadi baris dan kolom dan menjatuhkan baris / kolom kosong. Dalam implementasi ini "kosong" adalah kurang dari 1, dan hanya raster band tunggal yang diperhitungkan.
(Saya menyadari ketika saya menulis bahwa pendekatan scanline ini hanya cocok untuk gambar dengan "kerah" nodata. Jika data Anda adalah pulau-pulau di lautan nol, ruang antar pulau akan turun juga, menyelipkan semuanya bersama-sama, dan benar-benar mengacaukan georeferencing .)
Bagian bisnis (perlu disempurnakan, tidak akan berfungsi apa adanya):
#read raster into a numpy array
data = np.array(gdal.Open(src_raster).ReadAsArray())
#scan for data
non_empty_columns = np.where(data.max(axis=0)>0)[0]
non_empty_rows = np.where(data.max(axis=1)>0)[0]
# assumes data is any value greater than zero
crop_box = (min(non_empty_rows), max(non_empty_rows),
min(non_empty_columns), max(non_empty_columns))
# retrieve source geo reference info
georef = raster.GetGeoTransform()
xmin, ymax = georef[0], georef[3]
xcell, ycell = georef[1], georef[5]
# Calculate cropped geo referencing
new_xmin = xmin + (xcell * crop_box[0]) + xcell
new_ymax = ymax + (ycell * crop_box[2]) - ycell
cropped_transform = new_xmin, xcell, 0.0, new_ymax, 0.0, ycell
# crop
new_data = data[crop_box[0]:crop_box[1]+1, crop_box[2]:crop_box[3]+1]
# write to disk
band = out_raster.GetRasterBand(1)
band.WriteArray(new_data)
band.FlushCache()
out_raster = None
Dalam skrip lengkap:
import os
import sys
import numpy as np
from osgeo import gdal
if len(sys.argv) < 2:
print '\n{} [infile] [outfile]'.format(os.path.basename(sys.argv[0]))
sys.exit(1)
src_raster = sys.argv[1]
out_raster = sys.argv[2]
def main(src_raster):
raster = gdal.Open(src_raster)
# Read georeferencing, oriented from top-left
# ref:GDAL Tutorial, Getting Dataset Information
georef = raster.GetGeoTransform()
print '\nSource raster (geo units):'
xmin, ymax = georef[0], georef[3]
xcell, ycell = georef[1], georef[5]
cols, rows = raster.RasterYSize, raster.RasterXSize
print ' Origin (top left): {:10}, {:10}'.format(xmin, ymax)
print ' Pixel size (x,-y): {:10}, {:10}'.format(xcell, ycell)
print ' Columns, rows : {:10}, {:10}'.format(cols, rows)
# Transfer to numpy and scan for data
# oriented from bottom-left
data = np.array(raster.ReadAsArray())
non_empty_columns = np.where(data.max(axis=0)>0)[0]
non_empty_rows = np.where(data.max(axis=1)>0)[0]
crop_box = (min(non_empty_rows), max(non_empty_rows),
min(non_empty_columns), max(non_empty_columns))
# Calculate cropped geo referencing
new_xmin = xmin + (xcell * crop_box[0]) + xcell
new_ymax = ymax + (ycell * crop_box[2]) - ycell
cropped_transform = new_xmin, xcell, 0.0, new_ymax, 0.0, ycell
# crop
new_data = data[crop_box[0]:crop_box[1]+1, crop_box[2]:crop_box[3]+1]
new_rows, new_cols = new_data.shape # note: inverted relative to geo units
#print cropped_transform
print '\nCrop box (pixel units):', crop_box
print ' Stripped columns : {:10}'.format(cols - new_cols)
print ' Stripped rows : {:10}'.format(rows - new_rows)
print '\nCropped raster (geo units):'
print ' Origin (top left): {:10}, {:10}'.format(new_xmin, new_ymax)
print ' Columns, rows : {:10}, {:10}'.format(new_cols, new_rows)
raster = None
return new_data, cropped_transform
def write_raster(template, array, transform, filename):
'''Create a new raster from an array.
template = raster dataset to copy projection info from
array = numpy array of a raster
transform = geo referencing (x,y origin and pixel dimensions)
filename = path to output image (will be overwritten)
'''
template = gdal.Open(template)
driver = template.GetDriver()
rows,cols = array.shape
out_raster = driver.Create(filename, cols, rows, gdal.GDT_Byte)
out_raster.SetGeoTransform(transform)
out_raster.SetProjection(template.GetProjection())
band = out_raster.GetRasterBand(1)
band.WriteArray(array)
band.FlushCache()
out_raster = None
template = None
if __name__ == '__main__':
cropped_raster, cropped_transform = main(src_raster)
write_raster(src_raster, cropped_raster, cropped_transform, out_raster)
Skripnya ada di simpanan kode saya di Github, jika tautannya berbunyi 404; folder ini sudah matang untuk reorganisasi.
