Re: [Matplotlib-users] Matplotlib & Basemap / What is the Best Graphical Back-end for Raster Data Display (.png) ?

[Benjamin Root]

AGG is used for image handling, particularly for handling transforms,
scaling, interpolation and such. The AxesImage object that you get from
calling imshow() is handled through the AGG library. This is true
regardless of the backend being used because it is based in the AxesImage
class (and others). An SVG of a plot that used imshow() has raster data in
it that comes from AGG (and you can choose to rasterize other things, as
well). Cairo still needs the image buffer.

So, the distinction is the use of the AGG library, and the use of the AGG
backend. The AGG library is required, but the AGG backend is not (but
highly recommended).

I will admit that I didn't have this distinction very clear in my own head
until very recently when reviewing some PRs that reworked the image
handling architecture. I hope that clears it up for you, too.

Cheers!
Ben Root


On Thu, Mar 3, 2016 at 10:05 AM, Jerzy Karczmarczuk <
jerzy.karczmarc...@unicaen.fr> wrote:

> Le 03/03/2016 15:43, Benjamin Root a écrit :
> > Matplotlib will not work at all without AGG. Even the AGG-less
> > backends still use AGG for image handling (imshow() and such).
>
> Is it so? I never found such strong statement in the docs.
>
> 1. SVG backend produces vector graphics, no rasterisation in principle,
> so why AGG?
> 2. Cairo uses its own engine. Why AGG?
> 3. Image (PNG) "production" from curves, etc. uses AntiGrain, but if
> imshow() shows an image which is just a pixel array, there is no
> manipulation needing AGG, an element (triple RGB) becomes a pixel, and
> that's it.
>
> Jerzy Karczmarczuk
>
>
>
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