Figure.pygmtlogo: Force the default logo size to 2-cm and rename test_pygmtlogo to test_pygmtlogo_circle_no_wordmark

[seisman]

As shown in the table in PR #4616, we will likely have 24 PyGMT logo variants. Maintaining 24 separate baseline images is impractical, so we plan to group multiple variants into a single test. A reasonable approach is to define six tests based on logo shape and wordmark configuration. Each test would include four variants: colored and black-and-white logos in both light and dark themes.

This PR renames the existing test from test_pygmtlogo (which is too general) to test_pygmtlogo_circle_no_wordmark. It also adds a basemap to make the default logo size easier to inspect.

It appears that the default width/height of the logos is slightly smaller than 2 cm, although I am not sure why this value is used.

[seisman]

Other tests will be named like

• test_pygmtlogo_circle_horizontal_wordmark
• test_pygmtlogo_circle_vertical_wordmark
• test_pygmtlogo_hexagon_no_wordmark
• test_pygmtlogo_hexagon_horizontal_wordmark
• test_pygmtlogo_hexagon_vertical_wordmark

[seisman]

Plan to add the two black-and-white logos below the colored versions in later PRs.

[github-actions]

Summary of changed images

This is an auto-generated report of images that have changed on the DVC remote

Status	Path
added	pygmt/tests/baseline/test_pygmtlogo_circle_no_wordmark.png

Image diff(s)

Details

Added images

• test_pygmtlogo_circle_no_wordmark.png

Modified images

Path	Old	New

Report last updated at commit aafb290

[seisman]

It appears that the default width/height of the logos is slightly smaller than 2 cm, although I am not sure why this value is used.

One question, should we use the default logo size? I have no idea how the value is determined.

The default GMT logo is 2.54 cm high, and the "no label" version is close to 2 cm. Maybe we should force the PyGMT logo height to 2-cm for the no-wordmark and horizontal-wordmark version, and width to 2-cm for the vertical-wordmark version?

importpygmtfrompygmt.paramsimportPositionfig=pygmt.Figure()
fig.basemap(region=[0, 8, 0, 2], projection="x1c", frame="g1")
fig.logo(style="no_label")
fig.pygmtlogo(position=(6, 0))
fig.show()

[yvonnefroehlich]

It appears that the default width/height of the logos is slightly smaller than 2 cm, although I am not sure why this value is used.

One question, should we use the default logo size? I have no idea how the value is determined.

The default GMT logo is 2.54 cm high, and the "no label" version is close to 2 cm. Maybe we should force the PyGMT logo height to 2-cm for the no-wordmark and horizontal-wordmark version, and width to 2-cm for the vertical-wordmark version?

Hmm. This is an interesting question! I have to think about this tomorrow in more detail to understand the behaviour.

Currently we have in _create_logo:

size=4region= [-size, size] *2# -> 8 plot-unitsproj="x1c"# -> 1 cm per plot-units

I thougth the PyGMT logo saved to a file will have a size (diameter) of 8 cm for the circle version without wordmark.
For the PNG format (right), the default size is as expected when adding the image via Figure.image (code is at the end of the comment). But for the EPS format (left), the default size seems to be different:

---

Generating the PNG and EPS files with

size=1region= [-size, size] *2proj="x1c"

Leads to:

---

Setting position="jMC+jMC+w2c gives:

---

Code:

importpygmtfig=pygmt.Figure()
fig.basemap(region=[-4, 4] *2, projection="x1c", frame=1)
fig.image(imagefile="pygmt_logo_saved_external.eps")#, position="jMC+jMC+w2c")fig.basemap(frame="g1")
fig.shift_origin(xshift="+w+1c")
fig.basemap(region=[-4, 4] *2, projection="x1c", frame=1)
fig.image(imagefile="pygmt_logo_saved_external.png")#, position="jMC+jMC+w2c")fig.basemap(frame="g1")
fig.show()

[seisman]

From the image source code, it seems the default size is controlled by the GMT_GRAPHICS_DPU setting, which defaults to 300 dots per inch.

[yvonnefroehlich]

From the image source code, it seems the default size is controlled by the GMT_GRAPHICS_DPU setting, which defaults to 300 dots per inch.

Thanks for potting out this parameter, I did not know about it and that it affects the image module.

Currently we have

size=4region= [-size, size] *2# -> 8 plot-unitsproj="x1c"# -> 1 cm per plot-units

with GMT_GRAPHICS_DPU = 300 (default).

By only adding the logo image in EPS format (without a basemap) and using -V we can manually find out the width and hight after applying Figure.image. For the circle version (without the wordmark) the width (or hight) is the diameter.

importpygmtfig=pygmt.Figure()
fig.image(imagefile="pygmt_logo_saved_external.eps") # Logo is circle; use no basemap fig.show(V=True)

psconvert [INFORMATION]: Figure dimensions: Width: 54.4932 points [1.9224 cm] Height: 54.4932 points [1.9224 cm]

So we could either adjust size or GMT_GRAPHICS_DPU to make the default size of the logo (added via Figure.image using the EPS format) match 2 cm:

• size = (4 / 1.9224) * 2 = 4.161464835622139
• GMT_GRAPHICS_DPU = 300 - ((300/1.9224) * 2 - 300) = 287.8901373283396

Figure dimensions: Width: 56.7848 points [2.00324 cm] Height: 56.7848 points [2.00324 cm]

Not sure if this is an ideal solution.

[seisman]

I've rounded size to 4.1615 so the default logo width is ~2-cm.

[seisman]

I've rounded size to 4.1615 so the default logo width is ~2-cm.

Actually I feel this is not a good idea, since the actual size still depends on the GMT_GRAPHICS_DPU setting. Users would be surprised to see that GMT_GRAPHICS_DPU can affect the size of the default PyGMT logo size. I think the best solution is still to set the default logo size to 2-cm.

[yvonnefroehlich]

I've rounded size to 4.1615 so the default logo width is ~2-cm.

Actually I feel this is not a good idea, since the actual size still depends on the GMT_GRAPHICS_DPU setting. Users would be surprised to see that GMT_GRAPHICS_DPU can affect the size of the default PyGMT logo size. I think the best solution is still to set the default logo size to 2-cm.

I am fine with both ways.
My estimation is definitely not an elegant way to solve this issue 🙂. Besides the effect by GMT_GRAPHICS_DPU am I am especially surprised, that the default size depends on the file format.

[seisman]

Then I guess this PR can be approved and merged, right?

[yvonnefroehlich]

Then I guess this PR can be approved and merged, right?

Yes, sure. Sorry, did not see that you already changed code and docs.