kenji-miyake/how-to-generate-xyz-tiles-using-qgis3.md

## how-to-generate-xyz-tiles-using-qgis3.md

      
    Raw
  

              how-to-generate-xyz-tiles-using-qgis3.md
            
          
    How to generate XYZ tiles using QGIS3

Overview

QGIS3 has a tool called 'gdal2tiles.py' which can generate map tiles, but currently, it only supports TMS, not XYZ.
However, QGIS3 loads XYZ by default and requires checkbox for TMS, so it's better to convert TMS to XYZ.
The difference between TMS and XYZ is just the name of Y-coordinate, so renaming works well.
tms2xyz.py is a script for that.
Workflow

Suppose you have raster images with world files.

Generate GeoTIFF files

This command converts an image to GeoTIFF.
It's better to iterate files using shell script if you have many files.
gdal_translate -of GTiff -a_srs EPSG:{src-srs-number} {input-image-name} {output-tiff-name}

Merge GeoTIFF files to one file

First, list up file names of .tiff files.

Windows: dir /B {tiff-dir-name}\*.tiff > list.txt
Linux: ls {tiff-dir-name} | grep '.tiff' > list.txt

Then, create VRT(Virtual Dataset).
This is probably the fastest way to merge.
gdalbuildvrt -o merge.vrt -input_file_list list.txt
Finally, create a merged GeoTIFF file from VRT.
gdal_translate -ot Byte -co COMPRESS=LZW -co BIGTIFF=YES merge.vrt merge.tiff

Convert GeoTIFF to tiles

This command converts the merged GeoTIFF file to TMS tiles.
gdal2tiles -r "bilinear" -s "EPSG:{src-srs-number}" -z "16-20" --processes=8 merge.tiff tms-tiles

Convert TMS to XYZ

This command converts TMS tiles to XYZ tiles.
python tms2xyz.py tms-tiles xyz-tiles
See the following links for more options of GDAL commands.

https://gdal.org/programs/gdal_translate.html
https://gdal.org/programs/gdalbuildvrt.html
https://gdal.org/programs/gdal2tiles.html

References


https://gist.github.com/tmcw/4954720
https://gist.github.com/smnorris/4866ac1c17a37cab907d11d20de491dc
https://gist.github.com/kannes/ebfe021458f96e4f30b5
https://gis.stackexchange.com/questions/132242/what-are-the-differences-between-tms-xyz-wmts?noredirect=1&lq=1


## tms2xyz.py
import argparse
import shutil
from pathlib import Path

def tms2xyz(args):
  for old_path in args.input_tms_dir.glob(f'**/*{args.ext}'):
    z = int(old_path.parent.parent.stem)
    x = int(old_path.parent.stem)
    y = int(old_path.stem)

    new_y = 2**z - y - 1
    new_path = args.output_xyz_dir / str(z) / str(x) / (str(new_y) + args.ext)

    if args.verbose:
      print(f'{old_path} -> {new_path}')

    if not args.dry_run:
      new_path.parent.mkdir(parents=True, exist_ok=True)
      shutil.copy(old_path, new_path)

if __name__ == '__main__':
  parser = argparse.ArgumentParser(description="Convert TMS tiles to XYZ tiles")
  parser.add_argument('input_tms_dir', type=Path)
  parser.add_argument('-o', '--output_xyz_dir', type=Path, default='./xyz-tiles')
  parser.add_argument('-e', '--ext', default='.png')
  parser.add_argument('-v', '--verbose', action='store_true')
  parser.add_argument('--dry-run', action='store_true')
  args = parser.parse_args()

  tms2xyz(args)
	import argparse
	import shutil
	from pathlib import Path

	def tms2xyz(args):
	for old_path in args.input_tms_dir.glob(f'*/{args.ext}'):
	z = int(old_path.parent.parent.stem)
	x = int(old_path.parent.stem)
	y = int(old_path.stem)

	new_y = 2**z - y - 1
	new_path = args.output_xyz_dir / str(z) / str(x) / (str(new_y) + args.ext)

	if args.verbose:
	print(f'{old_path} -> {new_path}')

	if not args.dry_run:
	new_path.parent.mkdir(parents=True, exist_ok=True)
	shutil.copy(old_path, new_path)

	if __name__ == '__main__':
	parser = argparse.ArgumentParser(description="Convert TMS tiles to XYZ tiles")
	parser.add_argument('input_tms_dir', type=Path)
	parser.add_argument('-o', '--output_xyz_dir', type=Path, default='./xyz-tiles')
	parser.add_argument('-e', '--ext', default='.png')
	parser.add_argument('-v', '--verbose', action='store_true')
	parser.add_argument('--dry-run', action='store_true')
	args = parser.parse_args()

	tms2xyz(args)