Plotting text

It is often useful to add text annotations to a plot or map. This is handled by the pygmt.Figure.text method of the pygmt.Figure class.

from pathlib import Path

import pygmt

Adding a single text label

To add a single text label to a plot, use the text and x and y parameters to specify the text and position.

fig = pygmt.Figure()
fig.basemap(region=[-5, 5, -5, 5], projection="X5c", frame=True)
fig.text(x=0, y=0, text="My text")
fig.show()
text

Adjusting the text label

There are several optional parameters to adjust the text label:

  • font: Sets the size, family/weight, and color of the font for the text. A list of all recognized fonts can be found at PostScript Fonts Used by GMT, including details of how to use non-default fonts.

  • angle: Specifies the rotation of the text. It is measured counter-clockwise from the horizontal in degrees.

  • justify: Defines the anchor point of the bounding box for the text. It is specified by a two-letter (order independent) code, chosen from:

    • Vertical: T(op), M(iddle), B(ottom)

    • Horizontal: L(eft), C(entre), R(ight)

  • offset: Shifts the text relatively to the reference point.

fig = pygmt.Figure()

# -----------------------------------------------------------------------------
# Left: "font", "angle", and "offset" parameters
fig.basemap(region=[-5, 5, -5, 5], projection="X5c", frame="rtlb")

# Change font size, family/weight, color of the text
fig.text(x=0, y=3, text="my text", font="12p,Helvetica-Bold,blue")

# Rotate the text by 30 degrees counter-clockwise from the horizontal
fig.text(x=0, y=0, text="my text", angle=30)

# Plot marker and text label for reference
fig.plot(x=0, y=-3, style="s0.2c", fill="darkorange", pen="0.7p,darkgray")
fig.text(x=0, y=-3, text="my text")
# Shift the text label relatively to the position given via the x and y parameters
# by 1 centimeter to the right (positive x direction) and 0.5 centimeters down
# (negative y direction)
fig.text(x=0, y=-3, text="my text", offset="1c/-0.5c")

fig.shift_origin(xshift="w+0.5c")

# -----------------------------------------------------------------------------
# Right: "justify" parameter
fig.basemap(region=[-1, 1, -1, 1], projection="X5c", frame="rtlb")

# Plot markers for reference
fig.plot(
    x=[-0.5, 0, 0.5, -0.5, 0, 0.5, -0.5, 0, 0.5],
    y=[0.5, 0.5, 0.5, 0, 0, 0, -0.5, -0.5, -0.5],
    style="s0.2c",
    fill="darkorange",
    pen="0.7p,darkgray",
)

# Plot text labels at the x and y positions of the markers while varying the anchor
# point via the justify parameter
fig.text(x=-0.5, y=0.5, text="TL", justify="TL")  # TopLeft
fig.text(x=0, y=0.5, text="TC", justify="TC")  # TopCenter
fig.text(x=0.5, y=0.5, text="TR", justify="TR")  # TopRight
fig.text(x=-0.5, y=0, text="ML", justify="ML")  # MiddleLeft
fig.text(x=0, y=0, text="MC", justify="MC")  # MiddleCenter
fig.text(x=0.5, y=0, text="MR", justify="MR")  # MiddleRight
fig.text(x=-0.5, y=-0.5, text="BL", justify="BL")  # BottomLeft
fig.text(x=0, y=-0.5, text="BC", justify="BC")  # BottomCenter
fig.text(x=0.5, y=-0.5, text="BR", justify="BR")  # BottomRight

fig.show()
text

Adding a text box

There are different optional parameters to add and customize a text box:

  • fill: Fills the text box with a color.

  • pen: Outlines the text box.

  • clearance: Adds margins in x and y directions between the text and the outline of the text box. Can be used to get a text box with rounded edges.

fig = pygmt.Figure()

fig.basemap(region=[-5, 5, -5, 5], projection="X5c", frame="rtlb")

# Add a box with a fill in green color
fig.text(x=0, y=3, text="My text", fill="green")

# Add box with a seagreen, 1-point thick, solid outline
fig.text(x=0, y=1, text="My text", pen="1p,seagreen,solid")

# Add margins between the text and the outline of the text box of 0.1
# centimeters in x direction and 0.2 centimeters in y direction
fig.text(x=0, y=-1, text="My text", pen="1p,seagreen,dashed", clearance="0.1c/0.2c")

# Get rounded edges by passing "+tO" to the "clearance" parameter
fig.text(x=0, y=-3, text="My text", pen="1p,seagreen,solid", clearance="0.2c/0.2c+tO")

fig.show()
text

Adding multiple text labels with individual configurations

To add multiple text labels with individual font, angle, and justify, one can provide lists with the corresponding arguments.

fig = pygmt.Figure()
fig.basemap(region=[-5, 5, -5, 5], projection="X5c", frame=True)

fig.text(
    x=[0, 0, 0],
    y=[3, 2, -2],
    font=["5p,Helvetica,black", "5p,Helvetica,blue", "6p,Courier-Bold,red"],
    angle=[0, 0, 30],
    justify=["CM", "LT", "CM"],
    text=[
        "black text with justify='CM'",
        "blue text with justify='LT'",
        "red text with angle=30",
    ],
)

fig.show()
text

Using an external input file

It is also possible to add text labels via an external input file containing x, y, and text columns. Addionaly, columns to set the angle, front, and justify parameters can be provided. Here, we give a complete example.

fig = pygmt.Figure()
fig.basemap(region=[108, 121, -5, 8], projection="M10c", frame="a2f1")
fig.coast(land="darkgray", water="steelblue", shorelines="1/0.1p,gray30")

# Create space-delimited file with region / sea names:
# - longitude (x) and latitude (y) coordinates are in the first two columns
# - angle, font, and justify muss be present in this order in the next three columns
# - the text to be printed is given in the last column
with Path.open("examples.txt", "w") as f:
    f.write("114.00  0.50   0 15p,Helvetica-Bold,white CM BORNEO\n")
    f.write("119.00  3.25   0  8p,Helvetica-Bold,black CM CELEBES SEA\n")
    f.write("112.00 -4.60   0  8p,Helvetica-Bold,black CM JAVA SEA\n")
    f.write("112.00  6.00  40  8p,Helvetica-Bold,black CM SOUTH CHINA SEA\n")
    f.write("119.12  7.25 -40  8p,Helvetica-Bold,black CM SULU SEA\n")
    f.write("118.40 -1.00  65  8p,Helvetica-Bold,black CM MAKASSAR STRAIT\n")

# Setting the angle, font, and justify parameters to True indicates that those columns
# are present in the text file
fig.text(textfiles="examples.txt", angle=True, font=True, justify=True)

# Cleanups
Path("examples.txt").unlink()

fig.show()
text

Using the position parameter

Instead of using the x and y parameters, the position parameter can be specified to set the reference point for the text on the plot. As for the justify parameter, the position parameter is specified by a two-letter (order independent) code, chosen from:

  • Vertical: T(op), M(iddle), B(ottom)

  • Horizontal: L(eft), C(entre), R(ight)

This can be helpful to add a tag to a subplot or text labels out of the plot or map frame, e.g., for depth slices.

fig = pygmt.Figure()

# -----------------------------------------------------------------------------
# Left: Add a tag to a subplot
fig.basemap(region=[-5, 5, -5, 5], projection="X5c", frame=["WStr", "af"])

fig.text(
    text="(a)",
    position="TL",  # Top Left
    justify="TL",  # Top Left
    offset="0.1c/-0.1c",
)

fig.shift_origin(xshift="w+1c")

# -----------------------------------------------------------------------------
# Right: Add a text label outside of the plot or map frame
fig.basemap(region=[-30, 30, 10, 60], projection="L0/35/23/47/5c", frame=["wSnE", "af"])

fig.text(
    text="@@100 km",  # "@@" gives "@" in GMT or PyGMT
    position="TC",  # Top Center
    justify="MC",  # Middle Center
    offset="0c/0.2c",
    no_clip=True,  # Allow plotting outside of the map or plot frame
)

fig.show()
text

Advanced configuration

For crafting more advanced styles, including using special symbols and other character sets, be sure to check out the GMT documentation at https://docs.generic-mapping-tools.org/6.5/text.html and also the Technical References at https://docs.generic-mapping-tools.org/6.5/reference/features.html#placement-of-text. Good luck!

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