Brendan Barnwell wrote:
> I'm trying to find the quickest way to erase a rectangular area of
> the figure canvas. I tried using canvas.restore_region with the
> optional bbox argument, but there seems to be some mismatch between
> the measurement units of the saved buffer object and the currently
> shown data. For instance, if I have a Text object on my plot, I tried
> this:
>
> bbox = g.text.get_window_extent()
> canvas.restore_region(background, bbox)
>
> . . . but it does not correctly block out the text. (The restored
> rectangle from the background appears elsewhere on the axes.) How can
> I convert the buffer coordinates to the coordinates of the the
> displayed plot?
I'm sorry to bump my own post, but I would really appreciate some
help with this. I've been wrestling with it for a couple days now,
and I cannot figure out how the coordinate system of the saved canvas
is related to the axes coordinates. I have found that with
bbox.transformed(ax.transData) I can at least get the coordinates
scaled to fit on the axes, but they are still offset in position from
where the box actually appears on the canvas. I can't figure out how
to compute this offset.
By playing around with the coordinates manually, for instance, I've
found that adjusting x by -52 and y by 21 appears to line up the
canvas with the axes, but I can't see where these numbers -52 and 21
would come from. My saved canvas buffer's get_extents() method
returns (65, 50, 586, 443), so I thought that the appropriate offsets
would be 65 and 50, but that doesn't work.
So, what coordinates (x1, y1, x2, y2) do I need to use in
canvas.restore_region(savedBuffer, (x1, y1, x2, y2)) in order to
restore precisely the area of canvas occupied by a patch drawn at axis
coordinates (a1, b1, a2, b2)?
Thanks?
--
Brendan Barnwell
"Do not follow where the path may lead. Go, instead, where there is
no path, and leave a trail."
--author unknown
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