make a notebook for image_overlay

[andrewgiessel]

I'll do it with a PR that but just leaving it here for now.

[ocefpaf]

@andrewgiessel how about this one:

http://nbviewer.ipython.org/github/ocefpaf/folium_notebooks/blob/master/test_image_overlay_gulf_stream.ipynb

We still need one where the projection is needed to correct the image array.

@koldunovn We need to add the legend now!

[andrewgiessel]

Looks good!

Here is a png of an array that is in geodetic and needs to be projected to mercator to display correctly.

data = plt.imread('temps.png')
map1 = folium.Map(location=[0,0], zoom_start=1)
map1.image_overlay(temps, opacity=0.5, data_projection=None)
# vs
map2 = folium.Map(location=[0,0], zoom_start=1)
map2.image_overlay(temps, opacity=0.5, data_projection=True) #using current 0.1.6 syntax

[ocefpaf]

I am re-thinking and I believe it is better to avoid any re-projection inside folium. Lets just say it needs the image in Web Mercator and leave the transformation to the user. We can easily create example with your geodetic_to_mercator(), rasterio or cartopy. I will try this image later with rasterio and cartopy.

[ocefpaf]

I added an example warping the array with cartopy

import cartopy.crs as ccrs
from cartopy.img_transform import warp_array

source_extent = [lon.min(), lon.max(), lat.min(), lat.max()]

new_data = warp_array(colored_data,
                      target_proj=ccrs.GOOGLE_MERCATOR,
                      source_proj=ccrs.PlateCarree(),
                      target_res=data.shape,
                      source_extent=source_extent,
                      target_extent=None,
                      mask_extrapolated=False)

However, we cannot warp images with cartopy (See https://github.com/SciTools/cartopy/blob/master/lib/cartopy/img_transform.py#L93-L120). rasterio can warp images, but have an awkward API that I still haven't figure out.

[rsignell-usgs]

!convert GS.png -trim gulf_stream.png

this does not work on windows. convert is a windows command to convert a hard drive to another format. Isn't there a way to do this in python?

[ocefpaf]

there a way to do this in python?

Probably yes. Using PIL or Pillow. I will take a look at it.

[ocefpaf]

Two new way: http://nbviewer.ipython.org/github/ocefpaf/folium_notebooks/blob/master/test_image_overlay_gulf_stream.ipynb

Trimming with PIL/Pillow and plotting directly from the array without creating another image.

[ocefpaf]

@andrewgiessel I am closing this. But feel free to send more example to this repo 😉

[rsignell-usgs]

@ocefpaf, this requires folium 0.1.6. Can you make a folium 0.1.6 release so I can submit a PR to the ioos conda-recipes?

[ocefpaf]

Folium v0.1.6 still needs some polishing. I am aiming for this weekend...