feat: add sentinel 2 script#335
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Python script and Topo50 index sheets shapefile for processing Sentinel 2 imagery.
| rgb_files = glob.glob("R10m/*B0[2-4]_10m.jp2") | ||
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| blue = rgb_files[0] | ||
| green = rgb_files[1] | ||
| red = rgb_files[2] |
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If rgb_files is supposed to have exactly three files you can unpack all of them in one go:
| rgb_files = glob.glob("R10m/*B0[2-4]_10m.jp2") | |
| blue = rgb_files[0] | |
| green = rgb_files[1] | |
| red = rgb_files[2] | |
| blue, green, red = glob.glob("R10m/*B0[2-4]_10m.jp2") |
| import subprocess | ||
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| # user definated variables |
| TILE_INDEX = "nz-150k-tile-index.shp" | ||
| MIN = "800" | ||
| MAX = "3000" | ||
| CWD = "C:/Temp/image-processing/test" |
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"CWD" ("current working directory") has a specific meaning in operating systems, being the directory from which a program was executed (not the directory where the script lives). You can get this directory using os.getcwd().
| MAX = "3000" | ||
| CWD = "C:/Temp/image-processing/test" | ||
| SENTINEL_IMAGE_DIR = "R10m" | ||
| GDAL_DIR = "C:/Program Files/QGIS 3.34.4/apps/Python39/Scripts" |
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This is very brittle, because the directory path will be different for anyone using a different OS or version of QGIS. This can be made more flexible in a couple of ways:
- Pass the directory as an option, like
--gdal-dir="C:/Program Files/QGIS 3.34.4/apps/Python39/Scripts". - If files from that directory are discoverable by the surrounding shell, that is, if you can run for example
gdal_merge.pywithout specifying its directory, then you can useshutil.which("gdal_merge.py")to get its absolute path.
| if os.path.exists(path): | ||
| shutil.rmtree(path) |
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This is very risky! It would be pretty easy for a programming mistake to delete a bunch of files which shouldn't be deleted. I'd recommend either:
- raising an exception telling the user what to do, or
- using
tempfile.mkdtempto create a new random directory every run and tell the user which directory to look for their data in.
| """ | ||
| Create directors for the various processed images to be saved into. | ||
| """ | ||
| path = os.path.join(CWD, dir_name) |
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If you from os.path import join you can shorten these expressions. But this is a stylistic choice, so I'll leave it to you whether you want to do that.
| print("Merging image tiles into one RGB image") | ||
| subprocess.run( | ||
| [ | ||
| "python.exe", |
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If you run just "python" instead, it should work on other platforms without changes. But this line shouldn't even be necessary, since gdal_merge.py should be executable.
| ogr_info = subprocess.Popen( | ||
| ["ogrinfo", "-ro", "-al", TILE_INDEX], stdout=subprocess.PIPE | ||
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| # tile into Topo50 sheet extents | ||
| ogr_output = ogr_info.communicate()[0].decode("utf-8") |
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It looks like you run this and then just wait for it to finish immediately. In that case I'd recommend ogr_output = subprocess.run([…], capture_output=True, check=True, encoding="utf-8").output.
| MIN = "800" | ||
| MAX = "3000" |
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These are passed to gdal_translate -scale; based on its documentation, would it be useful to name them something like MIN_SCALE and MAX_SCALE?
| "1", | ||
| "255", |
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According to the documentation, "If omitted the output range is 0 to 255". Do we actually want to use the output range 1 to 255 instead?
| import os | ||
| import glob | ||
| import shutil | ||
| from osgeo import gdal |
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It doesn't look like you're using this import anywhere. Did you mean to change the subprocess uses below to use this library? That would be preferable.
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Python script and Topo50 index sheets shapefile for processing Sentinel 2 imagery.