Fonts and Labels

All text in anyplotlib — titles, axis labels, the colorbar label and texts markers — is drawn straight onto the canvas. Sizes are CSS pixels, and strings may use a small TeX subset inside $...$.

This example walks through the options for text markers added with add_texts(): size, weight, outline, rotation, anchor alignment and math, plus the panel’s own labels.

import numpy as np
import anyplotlib as apl

rng = np.random.default_rng(11)
# A busy, non-square image: 180 rows x 260 columns.
data = rng.standard_normal((180, 260)).cumsum(0).cumsum(1)
data = (data - data.min()) / np.ptp(data)
# Calibrated axes so the panel shows ticks and axis labels.  Marker offsets
# below stay in image pixels (column, row).
x_nm = np.arange(260) * 0.05
y_nm = np.arange(180) * 0.05


def panel(title):
    fig, ax = apl.subplots(1, 1, figsize=(560, 420))
    plot = ax.imshow(data, axes=[x_nm, y_nm], units="nm", cmap="gray")
    plot.set_title(title, fontsize=14)
    return fig, plot

Panel labels

Titles, axis labels and the colorbar label take an optional fontsize and the same $...$ markup as text markers.

fig, v = panel(r"Panel labels: $\lambda$ = 2.5 $\AA$")
v.set_xlabel(r"$x$ (nm)", fontsize=13)
v.set_ylabel(r"$y$ (nm)", fontsize=13)
v.set_colorbar_visible(True)
v.set_colorbar_label(r"Intensity ($\times 10^{3}$)", fontsize=11)
v.set_tick_label_size(11)
fig

Size and weight

fontsize and fontweight apply to the whole group, so labels that differ in either go in separate groups.

fig, v = panel("Size and weight")
for i, (size, weight) in enumerate([(12, "normal"), (16, "normal"),
                                    (16, "bold"), (24, "bold")]):
    v.add_texts([[12, 20 + 38 * i]], [f"{size} px {weight}"],
                name=f"size{i}", color="#ffeb3b",
                fontsize=size, fontweight=weight)
fig

Outline for legibility

Over a busy image a label can vanish into the background. An outline_color strokes a halo under the fill; outline_width sets its thickness in pixels.

fig, v = panel("Outline (halo)")
v.add_texts([[12, 40]], ["no outline"], name="plain",
            color="#ffffff", fontsize=20, fontweight="bold")
v.add_texts([[12, 100]], ["outline_color='black'"], name="halo",
            color="#ffffff", fontsize=20, fontweight="bold",
            outline_color="#000000", outline_width=4)
fig

Rotation

rotation is in radians (matplotlib’s TextCollection convention) and turns the label counter-clockwise about its anchor point.

fig, v = panel("Rotation about the anchor")
anchor = [40, 165]
v.add_points([anchor], name="anchor", sizes=4, color="#ff1744",
             facecolors="#ff1744")
for deg in (0, 45, 90):
    # Leading spaces push the text off the anchor dot.
    v.add_texts([anchor], [f"   rotation = {deg}\N{DEGREE SIGN}"],
                name=f"rot{deg}", color="#00e5ff", fontsize=16,
                outline_color="#000000", rotation=np.deg2rad(deg),
                verticalalignment="center")
fig

Alignment

horizontalalignment ("left", "center", "right") and verticalalignment ("top", "center", "bottom", "baseline") choose which point of the text sits on the anchor. The defaults, "left" and "top", hang the label below and to the right.

fig, v = panel("horizontal / vertical alignment")
cols = {"left": 45, "center": 130, "right": 215}
rows = {"top": 40, "center": 90, "bottom": 140}
for ha, x in cols.items():
    for va, y in rows.items():
        v.add_points([[x, y]], name=f"pt-{ha}-{va}", sizes=3,
                     color="#ff1744", facecolors="#ff1744")
        v.add_texts([[x, y]], [f"{ha}/{va}"], name=f"txt-{ha}-{va}",
                    color="#ffeb3b", fontsize=13, outline_color="#000000",
                    horizontalalignment=ha, verticalalignment=va)
fig

Math in labels

Text with an even number of $ signs is typeset: superscripts, subscripts, Greek letters and \mathrm{} for upright text. Weight and outline still apply. As in matplotlib, a string with a single (odd) $ is plain text, so prices and shell prompts draw as written.

fig, v = panel("TeX in text markers")
v.add_texts([[12, 25]], [r"$\mathrm{Fe} K_{\alpha}$ edge"], name="edge",
            color="#ffeb3b", fontsize=18, outline_color="#000000")
v.add_texts([[12, 65]], [r"$\sigma$ = $10^{-3}$ nm$^{-1}$"],
            name="sigma", color="#ffeb3b", fontsize=18, fontweight="bold",
            outline_color="#000000")
v.add_texts([[12, 105]], [r"$\Delta E \approx$ 1.2 eV"],
            name="delta", color="#00e5ff", fontsize=18,
            outline_color="#000000")
v.add_texts([[12, 145]], ["Plain text: $5 each"], name="plain",
            color="#ffffff", fontsize=16, outline_color="#000000")
fig

Live update

Every option can change after the label is drawn with set(...).

v.markers["texts"]["edge"].set(fontsize=22, fontweight="bold",
                               rotation=np.deg2rad(-8))
fig