Feature: add etopo plotting to stock_img

[smartlixx]

Rationale

Close #1734

Implications

None as far as I can see.

Example

import matplotlib.pyplot as plt
import cartopy.crs as ccrs

fig = plt.figure(figsize=[4, 6])
ax1 = fig.add_subplot(2, 1, 1, projection=ccrs.PlateCarree())
ax2 = fig.add_subplot(2, 1, 2, projection=ccrs.Orthographic())

ax1.stock_img(name='etopo')
ax1.coastlines()
ax2.stock_img(name='etopo')
ax2.coastlines()

plt.show()

The output is

[dopplershift]

Currently the PR is showing an empty etopo1.jpg committed? Any reason that needs to be included?

[smartlixx]

The file etopo1.jpg is not empty. its size is 1.28M (64 dpi). it is the picture of the bathymetry data to plot. I took it from Basemao repo, because the original file downloaded from NOAA is about 2M (96 dpi). This file definitely will increase the size of cartopy. Alternatively, we can download it on the fly from NOAA website. Please let me know your opinion.

[greglucas]

I think grabbing it from the source is better whenever possible, that way we get any updates they have. It also looks like there are multiple "versions" of etopo, focusing on ice, or other features too? It looks like the original data is 300+MB! I didn't see the downsampled version immediately on NOAA's site, do you have a link to that?

[smartlixx]

I think grabbing it from the source is better whenever possible, that way we get any updates they have. It also looks like there are multiple "versions" of etopo, focusing on ice, or other features too? It looks like the original data is 300+MB! I didn't see the downsampled version immediately on NOAA's site, do you have a link to that?

When you click on the thumbnail on https://www.ngdc.noaa.gov/mgg/global/, you will get to the downsampled version of etopo1: https://www.ngdc.noaa.gov/mgg/image/color_etopo1_ice_low.jpg.

Yes, there are several versions of this dataset, depending on using the ice top or the ice bottom for altitude. The above link should suffice for our purpose. If we choose to grab it on the fly, its size is about 2M.

[smartlixx]

Now I have modified the code to download the etopo1 image from NOAA website, and delete the etopo1.jpg file from the commit.

[dopplershift]

Can you rebase your commits to "squash" together the original commit adding the file and the one deleting it? Otherwise, there will be a copy of the 1.3MB file sitting in the history for this repo.

[smartlixx]

Can you rebase your commits to "squash" together the original commit adding the file and the one deleting it? Otherwise, there will be a copy of the 1.3MB file sitting in the history for this repo.

Thanks. I squashed all the commits into one.

The test failure message below seems not to be related with this PR.

FAILED lib/cartopy/tests/mpl/test_ticks.py::test_set_xticks_no_transform - Fi...

[marqh]

this PR appears to be reviwed and have passing tests, but there are conflicts between it and master

@smartlixx please may i suggest that you rebase this PR branch with respect to upstream/master

i would hope that reviewers would then be able to re-assess and potentially merge this onto master

@dopplershift @QuLogic is this reasonable from your points of view?

[smartlixx]

this PR appears to be reviwed and have passing tests, but there are conflicts between it and master

@smartlixx please may i suggest that you rebase this PR branch with respect to upstream/master

i would hope that reviewers would then be able to re-assess and potentially merge this onto master

@dopplershift @QuLogic is this reasonable from your points of view?

Yes, it is done. Please review and let me know your thoughts. @QuLogic @dopplershift

[greglucas]

Looks good to me, just one minor suggestion.

As a side comment/follow-up PR, would this make sense to have as a RasterSource feature artist? So, make it usable outside of the stock_img function, and have stock_img add the RasterSource features instead.

[smartlixx]

Looks good to me, just one minor suggestion.

Thanks for your comments. I have updated the PR to incorporate the new changes since my last commit, and the PR has passed all the test. Hopefully it can be accepted (quite a long time has passed). Or if it is OK, I can also combine this PR with #2230.

As a side comment/follow-up PR, would this make sense to have as a RasterSource feature artist? So, make it usable outside of the stock_img function, and have stock_img add the RasterSource features instead.

I can see there is a RasterSource class in io/__init__.py

cartopy/lib/cartopy/io/__init__.py

Lines 310 to 365 in a6c0835

	class RasterSource:
	"""
	Define the cartopy raster fetching interface.
	A :class:`RasterSource` instance is able to supply images and
	associated extents (as a sequence of :class:`LocatedImage` instances)
	through its :meth:`~RasterSource.fetch_raster` method.
	As a result, further interfacing classes, such as
	:class:`cartopy.mpl.slippy_image_artist.SlippyImageArtist`, can then
	make use of the interface for functionality such as interactive image
	retrieval with pan and zoom functionality.
	.. _raster-source-interface:
	"""
	def validate_projection(self, projection):
	"""
	Raise an error if this raster source cannot provide images in the
	specified projection.
	Parameters
	----------
	projection: :class:`cartopy.crs.Projection`
	The desired projection of the image.
	"""
	raise NotImplementedError()
	def fetch_raster(self, projection, extent, target_resolution):
	"""
	Return a sequence of images with extents given some constraining
	information.
	Parameters
	----------
	projection: :class:`cartopy.crs.Projection`
	The desired projection of the image.
	extent: iterable of length 4
	The extent of the requested image in projected coordinates.
	The resulting image may not be defined exactly by these extents,
	and so the extent of the resulting image is also returned. The
	extents must be defined in the form
	``(min_x, max_x, min_y, max_y)``.
	target_resolution: iterable of length 2
	The desired resolution of the image as ``(width, height)`` in
	pixels.
	Returns
	-------
	images
	A sequence of :class:`LocatedImage` instances.
	"""
	raise NotImplementedError()

This may be a good starting point, but it's beyond my hands at this moment.

[rcomer]

Hi, I’m just checking on the status of this one. It looks like it was ready to go but unfortunately now has conflicts with the main branch again. @smartlixx do you have the bandwidth to rebase this again?

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