Make plot resolution configurable

Set plotting resolution from workflow config via rose edit. The plot
resolution is then read via a function. This keeps importing the module
from having side effects.

Setting and getting plot resolution is tested.

cset-workflow/app/run_cset_recipe/bin/run-cset-recipe.py

@@ -159,6 +159,7 @@ def parallel():
                 f"--input-dir={data_directory()}",
                 f"--output-dir={output_directory()}",
                 f"--style-file={os.getenv('COLORBAR_FILE', '')}",
+                f"--plot-resolution={os.getenv('PLOT_RESOLUTION', '')}",
                 "--parallel-only",
             ),
             check=True,
@@ -188,6 +189,7 @@ def collate():
                 f"--recipe={recipe_file()}",
                 f"--output-dir={output_directory()}",
                 f"--style-file={os.getenv('COLORBAR_FILE', '')}",
+                f"--plot-resolution={os.getenv('PLOT_RESOLUTION', '')}",
                 "--collate-only",
             ),
             check=True,

cset-workflow/flow.cylc

@@ -72,6 +72,7 @@ URL = https://metoffice.github.io/CSET
         LOGLEVEL = {{LOGLEVEL}}
         WEB_DIR = {{WEB_DIR}}
         COLORBAR_FILE = {{COLORBAR_FILE}}
+        PLOT_RESOLUTION = {{PLOT_RESOLUTION}}
 
     [[PARALLEL]]
     script = rose task-run -v --app-key=run_cset_recipe

cset-workflow/meta/rose-meta.conf

@@ -171,6 +171,16 @@ help=
 type=quoted
 compulsory=true
 
+[template variables=PLOT_RESOLUTION]
+ns=General
+description=Resolution of output plot in dpi.
+help=This is passed through to the plotting operators and sets the resolution
+    of the output plots to the given number of pixels per inch. If unset
+    defaults to 100 dpi. The plots are all 8 by 8 inches, so this corresponds
+    to 800 by 800 pixels.
+type=integer
+compulsory=true
+
 [template variables=WEB_DIR]
 ns=General
 description=Path to directory that is served by the webserver.

src/CSET/__init__.py

@@ -76,6 +76,9 @@ def main():
     parser_bake.add_argument(
         "-s", "--style-file", type=Path, help="colour bar definition to use"
     )
+    parser_bake.add_argument(
+        "--plot-resolution", type=int, help="plotting resolution in dpi"
+    )
     parser_bake.set_defaults(func=_bake_command)
 
     parser_graph = subparsers.add_parser("graph", help="visualise a recipe file")
@@ -207,10 +210,15 @@ def _bake_command(args, unparsed_args):
             args.output_dir,
             recipe_variables,
             args.style_file,
+            args.plot_resolution,
         )
     if not args.parallel_only:
         execute_recipe_collate(
-            args.recipe, args.output_dir, recipe_variables, args.style_file
+            args.recipe,
+            args.output_dir,
+            recipe_variables,
+            args.style_file,
+            args.plot_resolution,
         )
 
 

src/CSET/operators/__init__.py

@@ -142,7 +142,14 @@ def _step_parser(step: dict, step_input: any) -> str:
         return operator(**kwargs)
 
 
-def _run_steps(recipe, steps, step_input, output_directory: Path, style_file: Path):
+def _run_steps(
+    recipe,
+    steps,
+    step_input,
+    output_directory: Path,
+    style_file: Path = None,
+    plot_resolution: int = None,
+) -> None:
     """Execute the steps in a recipe."""
     original_working_directory = Path.cwd()
     os.chdir(output_directory)
@@ -159,6 +166,8 @@ def _run_steps(recipe, steps, step_input, output_directory: Path, style_file: Pa
         # Create metadata file used by some steps.
         if style_file:
             recipe["style_file_path"] = str(style_file)
+        if plot_resolution:
+            recipe["plot_resolution"] = plot_resolution
         _write_metadata(recipe)
         # Execute the recipe.
         for step in steps:
@@ -174,6 +183,7 @@ def execute_recipe_parallel(
     output_directory: Path,
     recipe_variables: dict = None,
     style_file: Path = None,
+    plot_resolution: int = None,
 ) -> None:
     """Parse and executes the parallel steps from a recipe file.
 
@@ -188,8 +198,12 @@ def execute_recipe_parallel(
         input.
     output_directory: Path
         Pathlike indicating desired location of output.
-    recipe_variables: dict
+    recipe_variables: dict, optional
         Dictionary of variables for the recipe.
+    style_file: Path, optional
+        Path to a style file.
+    plot_resolution: int, optional
+        Resolution of plots in dpi.
 
     Raises
     ------
@@ -213,14 +227,15 @@ def execute_recipe_parallel(
         logging.error("Output directory is a file. %s", output_directory)
         raise err
     steps = recipe["parallel"]
-    _run_steps(recipe, steps, step_input, output_directory, style_file)
+    _run_steps(recipe, steps, step_input, output_directory, style_file, plot_resolution)
 
 
 def execute_recipe_collate(
     recipe_yaml: Union[Path, str],
     output_directory: Path,
     recipe_variables: dict = None,
     style_file: Path = None,
+    plot_resolution: int = None,
 ) -> None:
     """Parse and execute the collation steps from a recipe file.
 
@@ -234,6 +249,10 @@ def execute_recipe_collate(
         Pathlike indicating desired location of output. Must already exist.
     recipe_variables: dict
         Dictionary of variables for the recipe.
+    style_file: Path, optional
+        Path to a style file.
+    plot_resolution: int, optional
+        Resolution of plots in dpi.
 
     Raises
     ------
@@ -249,4 +268,6 @@ def execute_recipe_collate(
     recipe = parse_recipe(recipe_yaml, recipe_variables)
     # If collate doesn't exist treat it as having no steps.
     steps = recipe.get("collate", [])
-    _run_steps(recipe, steps, output_directory, output_directory, style_file)
+    _run_steps(
+        recipe, steps, output_directory, output_directory, style_file, plot_resolution
+    )

src/CSET/operators/plot.py

@@ -181,6 +181,11 @@ def _colorbar_map_levels(varname: str, **kwargs):
     return cmap, levels, norm
 
 
+def _get_plot_resolution() -> int:
+    """Get resolution of rasterised plots in pixels per inch."""
+    return get_recipe_metadata().get("plot_resolution", 100)
+
+
 def _plot_and_save_contour_plot(
     cube: iris.cube.Cube,
     filename: str,
@@ -248,7 +253,7 @@ def _plot_and_save_contour_plot(
     cbar.set_label(label=f"{cube.name()} ({cube.units})", size=20)
 
     # Save plot.
-    fig.savefig(filename, bbox_inches="tight", dpi=100)
+    fig.savefig(filename, bbox_inches="tight", dpi=_get_plot_resolution())
     logging.info("Saved contour plot to %s", filename)
     plt.close(fig)
 
@@ -311,7 +316,7 @@ def _plot_and_save_postage_stamp_contour_plot(
     # Overall figure title.
     fig.suptitle(title)
 
-    fig.savefig(filename, bbox_inches="tight", dpi=100)
+    fig.savefig(filename, bbox_inches="tight", dpi=_get_plot_resolution())
     logging.info("Saved contour postage stamp plot to %s", filename)
     plt.close(fig)
 
@@ -347,7 +352,7 @@ def _plot_and_save_line_series(
     ax.autoscale()
 
     # Save plot.
-    fig.savefig(filename, bbox_inches="tight", dpi=100)
+    fig.savefig(filename, bbox_inches="tight", dpi=_get_plot_resolution())
     logging.info("Saved line plot to %s", filename)
     plt.close(fig)
 
@@ -436,7 +441,7 @@ def _plot_and_save_vertical_line_series(
     ax.autoscale()
 
     # Save plot.
-    fig.savefig(filename, bbox_inches="tight", dpi=100)
+    fig.savefig(filename, bbox_inches="tight", dpi=_get_plot_resolution())
     logging.info("Saved line plot to %s", filename)
     plt.close(fig)
 
@@ -492,7 +497,7 @@ def _plot_and_save_scatter_plot(
     ax.autoscale()
 
     # Save plot.
-    fig.savefig(filename, bbox_inches="tight", dpi=100)
+    fig.savefig(filename, bbox_inches="tight", dpi=_get_plot_resolution())
     logging.info("Saved scatter plot to %s", filename)
     plt.close(fig)
 
@@ -551,7 +556,7 @@ def _plot_and_save_histogram_series(
     )
 
     # Save plot.
-    fig.savefig(filename, bbox_inches="tight", dpi=100)
+    fig.savefig(filename, bbox_inches="tight", dpi=_get_plot_resolution())
     logging.info("Saved line plot to %s", filename)
     plt.close(fig)
 
@@ -620,7 +625,7 @@ def _plot_and_save_postage_stamp_histogram_series(
     # Overall figure title.
     fig.suptitle(title)
 
-    fig.savefig(filename, bbox_inches="tight", dpi=100)
+    fig.savefig(filename, bbox_inches="tight", dpi=_get_plot_resolution())
     logging.info("Saved histogram postage stamp plot to %s", filename)
     plt.close(fig)
 
@@ -658,7 +663,7 @@ def _plot_and_save_postage_stamps_in_single_plot_histogram_series(
     ax.legend()
 
     # Save the figure to a file
-    plt.savefig(filename, bbox_inches="tight", dpi=100)
+    plt.savefig(filename, bbox_inches="tight", dpi=_get_plot_resolution())
 
     # Close the figure
     plt.close(fig)

tests/operators/test_plots.py

@@ -255,3 +255,17 @@ def test_scatter_plot_too_many_y_dimensions(
     cube_x = collapse.collapse(vertical_profile_cube, ["time"], "MEAN")[0:4]
     with pytest.raises(ValueError):
         plot.scatter_plot(cube_x, cube_y)
+
+
+def test_get_plot_resolution(tmp_working_dir):
+    """Test getting the plot resolution."""
+    with open("meta.json", "wt", encoding="UTF-8") as fp:
+        fp.write('{"plot_resolution": 72}')
+    resolution = plot._get_plot_resolution()
+    assert resolution == 72
+
+
+def test_get_plot_resolution_unset(tmp_working_dir):
+    """Test getting the default plot resolution when unset."""
+    resolution = plot._get_plot_resolution()
+    assert resolution == 100

tests/test_run_recipes.py

@@ -94,3 +94,11 @@ def test_run_steps_style_file_metadata_written(tmp_path: Path):
     with open(tmp_path / "meta.json", "rb") as fp:
         metadata = json.load(fp)
     assert metadata["style_file_path"] == style_file_path
+
+
+def test_run_steps_plot_resolution_metadata_written(tmp_path: Path):
+    """Style file path metadata written out."""
+    CSET.operators._run_steps({}, [], None, tmp_path, plot_resolution=72)
+    with open(tmp_path / "meta.json", "rb") as fp:
+        metadata = json.load(fp)
+    assert metadata["plot_resolution"] == 72