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Add gallery example for plotting an RGB image from an xarray.DataArray #2641

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Merged
merged 10 commits into from
Aug 30, 2023
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Add gallery example for plotting an RGB image from an xarray.DataArray #2641

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9d38316
Add gallery example for plotting an RGB image from an xarray.DataArray
weiji14 Aug 25, 2023
60d1be3
Add abbreviation for Cloud-Optimized GeoTIFF
weiji14 Aug 26, 2023
b516c19
Set title font to Times-Roman
weiji14 Aug 26, 2023
e7b66e6
Change apostrophe to Okina symbol ʻ
weiji14 Aug 26, 2023
9085f65
Inline comment on map scale projection
weiji14 Aug 26, 2023
4fd90be
Use ¯ and ` instead of \225 and \140
weiji14 Aug 26, 2023
7586ef7
Merge branch 'main' into gallery/rgb_image
weiji14 Aug 30, 2023
3c0712d
Force loading dataarray into memory
weiji14 Aug 30, 2023
00b427b
Apply suggestions from code review
weiji14 Aug 30, 2023
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weiji14 Aug 30, 2023
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39 changes: 39 additions & 0 deletions examples/gallery/images/rgb_image.py
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"""
RGB Image
---------
The :meth:`pygmt.Figure.grdimage` method can be used to plot Red, Green, Blue
(RGB) images, or any 3-band false color combination. Here, we'll use
:meth:`rioxarray.open_rasterio` to read a GeoTIFF file into an
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@yvonnefroehlich yvonnefroehlich Aug 30, 2023

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Is it possible to make this work as a link to https://corteva.github.io/rioxarray/stable/rioxarray.html#rioxarray.open_rasterio?

If this is not easy to do, then we leave it as is. At least in the code example below, the link works.

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@weiji14 weiji14 Aug 30, 2023

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Ah yes, good catch. I used the wrong intersphinx directive, should be :py:func:

Suggested change
:meth:`rioxarray.open_rasterio` to read a GeoTIFF file into an
:py:func:`rioxarray.open_rasterio` to read a GeoTIFF file into an

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@yvonnefroehlich yvonnefroehlich Aug 31, 2023

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Ah, great. Thanks!

:class:`xarray.DataArray` format, and plot it on a map.

The example below shows a Worldview 2 satellite image over
`Lāhainā, Hawaiʻi during the August 2023 wildfires
<https://en.wikipedia.org/wiki/2023_Hawaii_wildfires#L%C4%81hain%C4%81>`_.
Data is sourced from a Cloud-Optimized GeoTIFF (COG) file hosted on
`OpenAerialMap <https://map.openaerialmap.org>`_ under a
`CC BY-NC 4.0 <https://creativecommons.org/licenses/by-nc/4.0/>`_ license.
"""
import pygmt
import rioxarray

###############################################################################
# Read 3-band data from GeoTIFF into an xarray.DataArray object
image = rioxarray.open_rasterio(
filename="https://oin-hotosm.s3.us-east-1.amazonaws.com/64d6a49a19cb3a000147a65b/0/64d6a49a19cb3a000147a65c.tif",
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@seisman seisman Aug 26, 2023

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This GeoTiff file is almost 1 GB, which is too big to download.

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@weiji14 weiji14 Aug 26, 2023

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The next line overview_level=5 gets a reduced resolution version. Original image has shape (y: 115712, x: 99328), but at overview_level=5, the shape is (y: 1808, x: 1552).

overview_level=5,
)
# Subset to area of Lāhainā in EPSG:32604 coordinates
image = image.rio.clip_box(minx=738000, maxx=755000, miny=2300000, maxy=2318000)
image

###############################################################################
# Plot the RGB imagery
fig = pygmt.Figure()
with pygmt.config(FONT_TITLE="Times-Roman"): # Set title font to Times-Roman
fig.grdimage(
grid=image,
projection="x1:100000",
frame=[r"WSne+tL@!a\225hain@!a\225, Hawai\140i on 9 Aug 2023", "af"],
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@weiji14 weiji14 Aug 26, 2023

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Changed to using \140 instead of \047 as it looks a bit closer to the Okina ʻ letter (U+02BB) (see also #1474 (comment)). Now it looks like this:

Lāhainā, Hawaiʻi in Times-Roman font.

If anyone has ideas on how to use the actual Okina letter, let me know! I did try using ʻ directly, but it shows up like this:

Hawaiʻi with the Okina letter plotted incorrectly.

)
fig.savefig("Lāhainā.png")
fig.show()