Generating resized & rotated images with coastlines from composites in satpy

[Miruna]

Dear Pytrollists,

I am trying to generate images of the Airmass composite from MSG HRIT files, of a certain size, and with coastlines on top. I managed to do this in mpop with pycoast (ContourWriterAGG): I load the data, reproject it, generate the composite, then do the following:

- img=global_data.image.airmass()

-img_pil=img.pil_image()   

-cw.add_coastlines(img_pil,areadef,outline='black',width=1)

then I resize the image and save it to disk.

With satpy, I have the following issues:

1) Colours

If I load the composite in my Scene object and then do Scene.save_dataset, I get the colours I expect to get for Airmass, but with the globe upside down. To counter this, I convert the composite to a TrollImage (img=to_image(scene['airmass']), then to a PIL image (because I couldn't find a rotate function inside TrollImage, maybe I am missing it). The problem is that when I save this rotated PIL Image to disk, I do not get the same colours as when saving it with save_dataset from the Scene object. Also, if I save the TrollImage obtained via to_image from the composite, I don't get the expected colours. What additional steps (stretching, gamma etc.) would I need to apply to the Image object in order to get the same thing as with save_dataset?

2) Coastlines

With mpop, I was using ContourWriterAGG from pycoast, which needs as input parameter an area definition (from mpop.projector). How can I add coastlines in satpy? In the documentation of satpy, I found the method satpy.writers.add_overlay(orig, area, coast_dir, color=(0, 0, 0), width=0.5, resolution=None) but it's not clear to me how to use it. What is the "area" input parameter here?

Thank you very much for your help.

Miruna

[Martin Raspaud]

Dear Miruna,

1. trollimage doesn't have a rotate function, but it would be fairly easy to add: a pr is welcome😀. Maybe a more sustainable approach would be to flip the data at reading time. I think it shouldn't that hard to implement. 

2. For the coastlines, you could do the following, when you save the image:

scn.save_dataset('airmass', "./test.png", overlay={'coast_dir': '/data/my/shapefiles/', 'width':1})

Best regards

Martin 

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Martin Raspaud, PhD

Software engineer

SMHI, SE-60176

[Miruna]

Dear Martin,

Thank you! What about the colours, how can I obtain the same colours when saving the image (GeoImage or PIL) as when I save the dataset from the Scene object?

Best regards,

Miruna

[miruna stoicescu]

Dear Martin,

What about the resizing and the colour issue? I was converting to PIL image to be able to rotate and resize but I encountered this problem with the colourscale, not being the same as when I save the dataset from Scene. 

Regards,

Miruna

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[Christian Peters]

Dear Martin,

I tried to add coastlines with your provide line, but got this error:

local_scn.save_dataset('natural', 'my_nice_overview2_realistic.png', overlay={'coast_dir':'/root/GSHHS_shp/','width':'1'})

  File "/usr/local/lib/python2.7/dist-packages/satpy/scene.py", line 662, in save_dataset
    overlay=overlay, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/satpy/writers/__init__.py", line 369, in save_dataset
    dataset, self.enhancer, fill_value, overlay=overlay, decorate=decorate)
  File "/usr/local/lib/python2.7/dist-packages/satpy/writers/__init__.py", line 248, in get_enhanced_image
    add_overlay(img, dataset.info['area'], **overlay)
  File "/usr/local/lib/python2.7/dist-packages/satpy/writers/__init__.py", line 114, in add_overlay
    resolution=resolution, width=width, level=level_coast)
TypeError: add_coastlines() got an unexpected keyword argument 'width'

I figured out that I need to install AggDraw 1.3.
Nwo I get:

local_scn.save_dataset('natural', 'my_nice_overview2_realistic.png', overlay={'coast_dir':'/root/','width':'1'})
  File "/usr/local/lib/python2.7/dist-packages/satpy/scene.py", line 662, in save_dataset
    overlay=overlay, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/satpy/writers/__init__.py", line 369, in save_dataset
    dataset, self.enhancer, fill_value, overlay=overlay, decorate=decorate)
  File "/usr/local/lib/python2.7/dist-packages/satpy/writers/__init__.py", line 248, in get_enhanced_image
    add_overlay(img, dataset.info['area'], **overlay)
  File "/usr/local/lib/python2.7/dist-packages/satpy/writers/__init__.py", line 114, in add_overlay
    resolution=resolution, width=width, level=level_coast)
  File "/usr/local/lib/python2.7/dist-packages/pycoast/cw_agg.py", line 418, in add_coastlines
    y_offset=y_offset)
  File "/usr/local/lib/python2.7/dist-packages/pycoast/cw_base.py", line 598, in _add_feature
    x_offset=x_offset, y_offset=y_offset, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/pycoast/cw_base.py", line 575, in add_shapes
    **new_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/pycoast/cw_agg.py", line 62, in _draw_polygon
    kwargs['outline_opacity'])
TypeError: a float is required


What am I doing wrong??

Regards,

Christian

[Martin Raspaud]

Hi Christian,

Whithout having testing myself, did you try providing the width as a float ?

Best regards,

Martin

[Christian Peters]

Martin,

yes...I tried.

But it dosn't change anything.

The log with setting width=1.0 :

[INFO: 2018-01-22 14:09:39 : satpy.writers] Add coastlines and political borders to image.
[DEBUG: 2018-01-22 14:09:39 : satpy.writers] Automagically choose resolution h
Traceback (most recent call last):
  File "compute2.py", line 84, in <module>
    local_scn.save_dataset('natural', 'my_nice_overview2_realistic.png', overlay={'coast_dir':'/root/','width':'1.0'})

  File "/usr/local/lib/python2.7/dist-packages/satpy/scene.py", line 662, in save_dataset
    overlay=overlay, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/satpy/writers/__init__.py", line 369, in save_dataset
    dataset, self.enhancer, fill_value, overlay=overlay, decorate=decorate)
  File "/usr/local/lib/python2.7/dist-packages/satpy/writers/__init__.py", line 248, in get_enhanced_image
    add_overlay(img, dataset.info['area'], **overlay)
  File "/usr/local/lib/python2.7/dist-packages/satpy/writers/__init__.py", line 114, in add_overlay
    resolution=resolution, width=width, level=level_coast)
  File "/usr/local/lib/python2.7/dist-packages/pycoast/cw_agg.py", line 418, in add_coastlines
    y_offset=y_offset)
  File "/usr/local/lib/python2.7/dist-packages/pycoast/cw_base.py", line 598, in _add_feature
    x_offset=x_offset, y_offset=y_offset, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/pycoast/cw_base.py", line 575, in add_shapes
    **new_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/pycoast/cw_agg.py", line 62, in _draw_polygon
    kwargs['outline_opacity'])
TypeError: a float is required

Regards,

Christian

[Martin Raspaud]

Hi Christian,

I realise it's been a long time since your last email, but I was wondering if you had found a solution for this ? Otherwise, it might be an aggdraw problem.

Best regards,

Martin

[Christian Peters]

HI Martin,

no...I didn't got it working.

I hope there will be some more examples for satpy (with adding coastlines) in the future to get an idea how it works.

I managed it with mpop but not with satpy.

Regards,

Christian