celiagg Kiva backend #247

jwiggins · 2016-10-26T20:43:45Z

This requires https://github.com/celiagg/celiagg (or pip install celiagg!) to be built and installed.

This works fairly well now. We should discuss how to proceed.

codecov-io · 2016-10-26T20:52:53Z

Current coverage is 52.05% (diff: 100%)

Merging #247 into master will not change coverage

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corranwebster · 2016-10-27T09:09:53Z

kiva/pyagg.py

+                          'text_transform', 'font'])
+
+
+class GraphicsContext(object):


It might make sense to inherit from AbstractGraphicsContext or basecore2d.GraphicsContextBase. Although at this point it may be more hassle than its worth.

Ah, I see that you've registered it with the ABC below. Ignore the above, then.

corranwebster · 2016-10-27T09:10:13Z

Yay! Will try this out at some point soon.

corranwebster · 2016-10-27T09:14:26Z

kiva/pyagg.py

+        raise NotImplementedError(msg)
+
+    def set_text_drawing_mode(self):
+        """ XXX: What is this for??


This is how to draw text: filled, outline, etc. See constants.py for the options.

Ahhh... You can probably see that I based this on the QPainter backend. Also, based on what I've read in the AGG backend, this isn't possible to implement there (fonts are raster only).

Do you know of a backend which implements this correctly? Quartz?

Yep, Quartz, although it is cheating somewhat because it just maps to the appropriate Quartz constant and passes it through to Quartz's corresponding method.

The raster-only stuff is likely why the current agg backend has a vendorized freetype2. Eg. see https://github.com/enthought/enable/blob/master/kiva/agg/src/kiva_graphics_context_base.cpp#L579, https://github.com/enthought/enable/blob/master/kiva/agg/src/kiva_graphics_context_base.cpp#L644 and https://github.com/enthought/enable/blob/master/kiva/agg/src/kiva_graphics_context.h#L1286

There are ctypes-based FreeType wrappers for Python (eg. https://pypi.python.org/pypi/freetype-py/) but I don't think they will help. I didn't see a Cython-based wrapper, which would be nicer for this use case.

pyagg already has support for vector and raster font representations. In fact, I've got it hard-coded to use vectors in the current backend code (see agg.FontCacheType.VectorFontCache in the set_font method). That should basically cover it, right (minus the complication of switching between representations in the Font instances)?

Yes, if pyagg has vector font support that should cover it if you can specify the render method (fill, stroke, etc.) for the vector path of the text.

Implemented!

jwiggins · 2016-10-29T15:53:28Z

I removed some previously committed changes to the examples... Force pushed. Mind the gap.

This is almost usable now. 😄

The pyagg backend is now functionally complete!

jwiggins · 2016-10-29T21:20:39Z

This is now functionally complete. Bugs included at no extra cost to you!

Also, fixed the implementation of CompiledPath.add_path

jwiggins · 2016-10-30T22:22:52Z

I've fixed all the bugs I could find. This actually works pretty well with all of the Chaco demos now!

Still faking it, but just about making it!

This was introduced by recent pyagg API changes

corranwebster · 2016-12-22T14:33:06Z

Playing around with this right now. I noticed that there are some artifacts when using gc.draw_image and not aligned to exact pixel edges. Eg.

gc.draw_image(a, (200, 400, 100, 100))

looks like this:

(notice line at right border) where if I force image to draw precisely on pixel boundaries, eg.

gc.draw_image(a, (200.5, 400.5, 100, 100))

there is no such problem:

Possibly related to the alpha?

Image is generated by:

a = np.empty((100, 100, 4), dtype='uint8')
a[:, :, 0] = np.linspace(0, 255, 100)
a[:, :, 1] = np.linspace(0, 255, 100).reshape(-1, 1)
a[:, :, 2] = np.linspace(255, 0, 100)
a[:, :, 3] = np.linspace(255, 0, 100).reshape(-1, 1)

corranwebster · 2016-12-22T14:46:39Z

Not sure if I should be putting these into the celiagg repo or here?

There is an issue that coloring isn't working for fonts. In the default kiva_explorer.py script, the fonts should be coloured like this:

but instead are just rendererd in black

(although FWIW the text layout is better)

corranwebster · 2016-12-22T15:02:45Z

To answer the question about how to proceed. There are two ways we could do this:

the way that this is structured now, where we have the current Agg backend and the new Celiagg backend and you access them with ETS_TOOLKIT=....celiagg or whatever. We would need to be careful about use of the current Image graphics context and code shouldn't assume the existence of Agg or Celiagg for rendering images (maybe lean more heavily on Pillow for that stuff).
we replace the Agg backend with the Celiagg backend everywhere. We'd need Celiagg to be reasonably feature-comparable to the current backend before doing this.

I'm not sure which is best. I'd be happy to see the back of the current Agg wrappers, but they work for the most part, so it may make sense to have a more gradual transition

jwiggins · 2016-12-22T18:39:25Z

The font color issue is an interesting one. If you try kiva_explorer.py with the Quartz backend, you will see that it matches celiagg. Basically, some backends use stroke color for text, others use fill color. I kinda punted and followed Quartz, but honestly it's not hard to change.

corranwebster · 2016-12-23T08:36:05Z

Hmmm... The qpainter backend also uses stroke color for text. Given that changing those is likely to be difficult (QPainter is just reflecting the underlying behaviour of Qt, I imagine Quartz is similar) I'm willing to live with using set_stroke_color instead of set_fill_color for celiagg.

Making sure we are consistent in the change throughout the dependent codebases will be a little finicky.

corranwebster · 2016-12-23T10:16:22Z

Thought a bit more about the way forward. I'm happy for this to be merged as-is so that we can work on further improvements based on this. We can revisit what to do with the current agg backend as things go forward.

jwiggins · 2016-12-23T14:23:22Z

I'd like to explore the image drawing issue a little bit first, but I suspect that it lies completely within celiagg. We shall see.

After that, yes, I think this should just be merged since it's not disruptive on its own. Then we can begin to discuss the more disruptive changes.

jwiggins · 2016-12-23T19:59:47Z

Okie dokie. I'm pulling the trigger. Thanks for the feedback Corran!

corranwebster reviewed Oct 27, 2016

View reviewed changes

Rough implementation of a pyagg kiva backend [ci skip]

7172029

jwiggins force-pushed the feat/pyagg-backend branch from 4f7bd69 to 7172029 Compare October 29, 2016 15:51

jwiggins added 2 commits October 29, 2016 21:30

Fix clip_to_rect and draw_image

f0a9204

Implement the last of the missing features

1e8df2a

The pyagg backend is now functionally complete!

Fix draw_path_at_points! [ci skip]

393a6b2

Also, fixed the implementation of CompiledPath.add_path

jwiggins force-pushed the feat/pyagg-backend branch from 758c9be to 393a6b2 Compare October 30, 2016 22:21

Implement get_text_extent a little better. [ci skip]

3a1274f

Still faking it, but just about making it!

jwiggins changed the title ~~[WIP]: pyagg Kiva backend~~ pyagg Kiva backend Oct 30, 2016

jwiggins added 4 commits November 1, 2016 23:06

Match changes made to pyagg

cb4d568

Add support for more pixel formats

1b398ea

Fix a bug in clipping

4d6ebb3

This was introduced by recent pyagg API changes

Rename pyagg -> celiagg [ci skip]

e2ef36f

jwiggins changed the title ~~pyagg Kiva backend~~ celiagg Kiva backend Nov 9, 2016

corranwebster added this to the 5.0.0 Release milestone Dec 19, 2016

jwiggins mentioned this pull request Dec 23, 2016

Use bilinear filtering for draw_image w/ non-simple transformation celiagg/celiagg#32

Merged

jwiggins merged commit 04d82e0 into master Dec 23, 2016

jwiggins deleted the feat/pyagg-backend branch December 23, 2016 20:00

jdeschenes mentioned this pull request Jul 23, 2017

Difference in rendering issues with celiagg celiagg/celiagg#43

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celiagg Kiva backend #247

celiagg Kiva backend #247

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celiagg Kiva backend #247

celiagg Kiva backend #247

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jwiggins commented Oct 26, 2016 • edited Loading

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Current coverage is 52.05% (diff: 100%)

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