matplotlib-users

[Matplotlib-users] bluemarble is too dark

[Dr. P. M. F. <pfe...@ve...>]

When I generate a map with a background generated via Basemap.bluemarble(),
the background is extremely dark.  Is there any way to get a
lighter/brighter version?  (I've looked at all of the available parameters,
but none of them seems to allow for adjustment of the luminance).
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Re: [Matplotlib-users] bluemarble is too dark

[Jose Gomez-D. <jgo...@gm...>]

Hi,

2009/12/14 Dr. Phillip M. Feldman <pfe...@ve...>

> When I generate a map with a background generated via Basemap.bluemarble(),
> the background is extremely dark.  Is there any way to get a
> lighter/brighter version?  (I've looked at all of the available parameters,
> but none of them seems to allow for adjustment of the luminance).
>

I find this problem when generating a PDF and viewing it in Linux,but the
on-screen version seems to work fine. One reason for your darkness might be
the actual bluemarble scene. There is one for every month <
http://earthobservatory.nasa.gov/Features/BlueMarble/>, so you can have a
look at the different month and pick u which is better for your
area/application. Another thing you can do is to modify the bluemarble that
comes with matplotlib using the gimp, as it is just an image file you can
edit easily. Starts looking like data cooking, tho' ;-)

J

Re: [Matplotlib-users] bluemarble is too dark

[Phillip M. F. <pfe...@ve...>]

Hello Jose-

I searched the Python installation on my computer, but have not been 
able to find the bluemarble image.

I also followed the link that you provided, but didn't find any images 
that cover the entire surface of the Earth.

Python Developers-

I'd really like to have an option in Basemap.bluemarble() to select from 
a set of images, rather than just having a single hardwired image.

Phillip

Jose Gomez-Dans wrote:
> Hi,
>
> 2009/12/14 Dr. Phillip M. Feldman <pfe...@ve... 
> <mailto:pfe...@ve...>>
>
>     When I generate a map with a background generated via
>     Basemap.bluemarble(),
>     the background is extremely dark.  Is there any way to get a
>     lighter/brighter version?  (I've looked at all of the available
>     parameters,
>     but none of them seems to allow for adjustment of the luminance).
>
>
> I find this problem when generating a PDF and viewing it in Linux,but 
> the on-screen version seems to work fine. One reason for your darkness 
> might be the actual bluemarble scene. There is one for every month 
> <http://earthobservatory.nasa.gov/Features/BlueMarble/>, so you can 
> have a look at the different month and pick u which is better for your 
> area/application. Another thing you can do is to modify the bluemarble 
> that comes with matplotlib using the gimp, as it is just an image file 
> you can edit easily. Starts looking like data cooking, tho' ;-)
>
> J 

Re: [Matplotlib-users] bluemarble is too dark

[Jeff W. <js...@fa...>]

Phillip M. Feldman wrote:
> Hello Jose-
>
> I searched the Python installation on my computer, but have not been 
> able to find the bluemarble image.
>
> I also followed the link that you provided, but didn't find any images 
> that cover the entire surface of the Earth.
>
> Python Developers-
>
> I'd really like to have an option in Basemap.bluemarble() to select from 
> a set of images, rather than just having a single hardwired image.
>   

You already can.

See the documentation for the warpimage method at 
http://matplotlib.sourceforge.net/basemap/doc/html/api/basemap_api.html.

-Jeff
> Phillip
>
> Jose Gomez-Dans wrote:
>   
>> Hi,
>>
>> 2009/12/14 Dr. Phillip M. Feldman <pfe...@ve... 
>> <mailto:pfe...@ve...>>
>>
>>     When I generate a map with a background generated via
>>     Basemap.bluemarble(),
>>     the background is extremely dark.  Is there any way to get a
>>     lighter/brighter version?  (I've looked at all of the available
>>     parameters,
>>     but none of them seems to allow for adjustment of the luminance).
>>
>>
>> I find this problem when generating a PDF and viewing it in Linux,but 
>> the on-screen version seems to work fine. One reason for your darkness 
>> might be the actual bluemarble scene. There is one for every month 
>> <http://earthobservatory.nasa.gov/Features/BlueMarble/>, so you can 
>> have a look at the different month and pick u which is better for your 
>> area/application. Another thing you can do is to modify the bluemarble 
>> that comes with matplotlib using the gimp, as it is just an image file 
>> you can edit easily. Starts looking like data cooking, tho' ;-)
>>
>> J 
>>     

Re: [Matplotlib-users] bluemarble is too dark

[Jouni K. S. <jk...@ik...>]

Jose Gomez-Dans <jgo...@gm...> writes:

> I find this problem when generating a PDF and viewing it in Linux,but the
> on-screen version seems to work fine. 

While the PDF format has advanced support for different color spaces and
rendering intents, the current PDF backend just uses DeviceRGB and
whatever the default rendering intent is. I wonder if some kind of
different color space or such setting would help - but this is a subject
that I know almost nothing about, and the PDF support is so complex that
I don't even know what the next reasonable step would be above just
using DeviceRGB.

Does the bluemarble image come with a specification or documentation
that mentions a color space, or what the pixel values are supposed to
mean, or how they are recommended to be rendered?

> Another thing you can do is to modify the bluemarble that
> comes with matplotlib using the gimp, as it is just an image file you can
> edit easily. Starts looking like data cooking, tho' ;-)

The fact is that different devices (displays, printers, projectors) have
different gamuts, and unless there is a specified color space, a set of
pixel values has no "right" mapping to the colors of the gamut (and even
if the space is known, mapping out-of-gamut colors can be done in
several ways). So I wouldn't call it "data cooking" if you are just
trying to get a reasonable contrast in your visualization of some data
that consists of values in some arbitrary space, although of course it
will not be any kind of true-color image either.

-- 
Jouni K. Seppänen
http://www.iki.fi/jks