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Figure.image: Add the alias 'invert' for option -I #4089

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Figure.image: Add the alias 'invert' for option -I #4089

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6 changes: 6 additions & 0 deletions pygmt/src/image.py
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ def image(
imagefile: PathLike,
projection=None,
box: Box | bool = False,
invert: bool = False,
verbose: Literal["quiet", "error", "warning", "timing", "info", "compat", "debug"]
| bool = False,
panel: int | tuple[int, int] | bool = False,
Expand All @@ -35,6 +36,7 @@ def image(

{aliases}
- F = box
- I = invert
- J = projection
- V = verbose
- c = panel
Expand Down Expand Up @@ -68,6 +70,9 @@ def image(
to make those pixels transparent. Can be repeated with different
settings. Alternatively, for color images you can select a single
*color* that should be made transparent instead (**+t**).
invert
Invert 1-bit image before plotting, i.e., black pixels (on) becomes white (off)
and vice versa. Ignored if used with color images.
Comment on lines +73 to +75
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@yvonnefroehlich yvonnefroehlich Sep 15, 2025 •
edited
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Hm, just trying this and maybe I am missing something here. I thought the remote raster image "vader1.png" is such a 1-bit image (see the last example at https://docs.generic-mapping-tools.org/dev/image.html#examples), but using I=True does not flip the black and white pixels as expected:

import pygmt

fig = pygmt.Figure()
fig.basemap(region=[-5, 5] * 2, projection="X3c/1c", frame=0)

fig.image(imagefile="@vader1.png", position="jLM")
fig.image(imagefile="@vader1.png", position="jMC", bitcolor=["gray+f", "blue+b"])
fig.image(imagefile="@vader1.png", position="jRM", I=True)  # Does not do something
# fig.image(imagefile="@vader1.png", position="jRM", bitcolor=["black+f", "white+b"])

fig.show()
image_invert

Same for

gmt image @vader1.png -I -png image_I_gmt
image_I_gmt

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Hmm, it looks like an upstream bug.

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I tested it with the gmt dev version, and still no inverted colors. Thus, I wrote an issue report at GenericMappingTools/gmt#8795.

monochrome : bool
Convert color image to monochrome grayshades using the (television)
YIQ-transformation.
Expand All @@ -80,6 +85,7 @@ def image(

aliasdict = AliasSystem(
F=Alias(box, name="box"),
I=Alias(invert, name="invert"),
).add_common(
J=projection,
V=verbose,
Expand Down
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