Transparency
lazarus / 55-TAChart

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Ask · 2012-09-01 15:48

After a lot of investigation, I have finally found a method to
implement transparency in TAChart.

Since r38472, you can set Series.Transparency to a value between 0
(opaque) and 255 (fully transparent). The actual effect you see
depends on the drawing back-end.
BGRABitmap offers the best support, AggPas, SVG and Canvas (the
default) support is "good enough", and other back-ends currently
ignore transparency.

So first, if anyone is interested, please test -- especially the
default drawer on non-Windows widgetsets.
Second, I have a few questions for maintainers of LCL and various
graphics libraries:

1) Transparency support for the canvas drawer is quite a hack: see
source. Is there a better way? (I think not, but maybe I missed
something). Is it portable enough?
2) Is there a way to support transparency at the TFPCustomCanvas
level? (Again, I think not)
3) Are there any plans for transparency support in FPVectorial?
4) Does anyone have any idea about possibility to support transparency
on printer canvas?

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wp · 2012-09-01 16:29

Tested only the canvas, and on Windows -- very impressive, excellent
work