Idea: enable customization of ACI RGB values for drawing add-on export

[seanpk]

Simply provide some greater control over the colors used to render ACI colors from the drawing add-on.

It is useful to adjust the colors to have better contrast on some background (it is already possible to set the background color and the contrast color with LayoutProperties). It could also be useful to force all elements to a single color, say blue, to provide a simplified visual, say like a blueprint.

Just "reaching into" the ezdxf.colors module and changing the color values in the DXF_DEFAULT_COLORS and DXF_DEFAULT_PAPERSPACE_COLORS lists doesn't seem to have the intended effect.

I could work on a PR, assuming this would be a welcome feature.

[seanpk]

hmm. I just noticed this comment at the top of the draw_layout() implementation in frontend.py, is it related to how it seemed that setting values in those lists didn't work:

        if layout_properties is not None:
            # TODO: this does not work, layer properties have to be re-evaluated!
            self.ctx.current_layout_properties = layout_properties
        else:
            self.ctx.set_current_layout(layout)

[mozman]

This seems to be an old comment, the feature works as expected in the qsave() function of the Matplotlib backend.

This is an old feature, it is better to set the layout properties by the config settings color_policy and background_policy.

[seanpk]

ok, that is good, I will check with those

[mozman]

The ColorPolicy does what you want.

# black and white output
config = Configuration(
    color_policy = ColorPolicy.BLACK,
    background_policy=BackgroundPolicy.WHITE,  
)

# or map all colors to custom color
config = Configuration(
    color_policy = ColorPolicy.CUSTOM,
    custom_fg_color = "#FF0000",
    background_poliy=BackgroundPolicy.CUSTOM,
    custom_bg_color = "#0000FF",
)

frontend = Frontend(
    ctx=RenderContext(doc), 
    out=svg.SVGBackend(), 
    config=config,
)

Additional ways to override the ACI

The way CAD applications allow users to set their own ACI colors is the .ctb plot style file and they have GUI applications to manage these .ctb files. Ezdxf can load and create .ctb files via the ezdxf.addons.acadctb add-on.

The .ctb file is evaluated by the RenderContext class, and this class is also the point where to override the associated .ctb file stored in the LAYOUT entity. Ezdxf searches the support directories defined in the config file for the .ctb files.

Override .ctb files:

   ctx = RenderContext(doc, ctb="your.ctb")

Another way to override the default ACI colors is to inherit from the Frontend class and override the override_properties() method:

class MyFrontend(Frontend):
    def override_properties(self, entity: DXFGraphic, properties: Properties) -> None:
        if properties.pen = 7:  # the ACI
            properties.color = "#AABBCC"

These are old features and there are better ways to do that. The override_properties() method should be a function to pass in and not a method to override. The .ctb file should be set as an acadctb.PlotStyle instance, so you don't have to load it from the file system and you can create a new one on the fly in the script.

But the drawing add-on is complex and I don't want to break existing code.

EDIT: I can/will fix this two problems without breaking existing code.

[seanpk]

What a great answer! I will make use of the capabilities that exist now and look forward to those two fixes/features becoming available. If there is anything I can do to assist, let me know :-)

Thank you!