Coordinate transforms — pin markers to the axes or the screen

Every add_* marker method takes a transform that decides which coordinate system its positions live in:

• "data" (default) — data coordinates; the marker moves and scales with zoom / pan, staying glued to the underlying data.

• "axes" — axes-normalised (0, 0) bottom-left … (1, 1) top-right; the marker stays in the same corner of the panel no matter how you zoom.

• "display" — raw CSS pixels within the panel; a fixed-size decoration.

The "axes" and "display" transforms are how you build overlays that should not track the data — a navigation index in the corner, a scale bar, a persistent legend chip.

import numpy as np
import anyplotlib as apl

rng  = np.random.default_rng(1)
data = rng.standard_normal((128, 128)).cumsum(0).cumsum(1)
data = (data - data.min()) / (data.max() - data.min())
xy   = np.linspace(0, 10, 128)

fig, ax = apl.subplots(1, 1, figsize=(480, 480))
v = ax.imshow(data, axes=[xy, xy], units="nm")

# Data-anchored label — sits at (5, 5) in nm and rides along on zoom/pan.
v.add_texts(offsets=[(5, 5)], texts=["feature @ (5, 5)"],
            color="#ffffff", fontsize=12, name="data_label")

# Axes-anchored index — stays pinned to the top-left corner of the panel
# regardless of zoom (0, 1 = top-left in axes fractions).
v.add_texts(offsets=[(0.04, 0.96)], texts=["frame 3 / 20"],
            transform="axes", color="#ffd54f", fontsize=13, name="nav_index")

fig

Try it

Zoom into the image: the white feature label moves with the data, while the yellow frame 3 / 20 index stays locked to the corner — because it is positioned in "axes" coordinates.

fig.set_help("Zoom in: the corner index stays put; the data label moves.")

fig  # Interactive

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