Render eqn utility

Author: swo

docs/render_eq.py

@@ -0,0 +1,71 @@
+"""
+Render equation block as a png
+"""
+
+import subprocess
+import tempfile
+from pathlib import Path
+
+import pdf2image
+
+
+def get_eqn(path="docs/lpl.md") -> str:
+    """Collect the first back-ticked math block from `path`"""
+    lines = []
+    in_eq = False
+    with open(path) as f:
+        for line in f:
+            line = line.strip()
+            if not in_eq and line == "```math":
+                in_eq = True
+            elif in_eq and line == "```":
+                in_eq = False
+                break
+            elif in_eq:
+                lines.append(line)
+            else:
+                pass
+
+    return "\n".join(lines)
+
+
+def latex_to_png(latex_str: str, out_path: str, dpi: int = 400, verbose: bool = False):
+    """Render `latex_str` using pdflatex"""
+    content = (
+        r"""
+\documentclass[preview,border=2pt]{standalone}
+\usepackage{amsmath,amssymb}
+\begin{document}
+%s
+\end{document}
+"""
+        % latex_str
+    )
+
+    with tempfile.TemporaryDirectory() as td:
+        path = Path(td) / "eq.tex"
+        path.write_text(content)
+        result = subprocess.run(
+            [
+                "pdflatex",
+                "-interaction=nonstopmode",
+                "-output-directory",
+                td,
+                str(path),
+            ],
+            capture_output=True,
+        )
+
+        if verbose:
+            print(result.stdout.decode("utf-8"))
+            print(result.stderr.decode("utf-8"))
+
+        pages = pdf2image.convert_from_path(str(Path(td) / "eq.pdf"), dpi=dpi)
+
+    pages[0].save(out_path, "PNG")
+
+
+if __name__ == "__main__":
+    eqn = get_eqn()
+    print(eqn)
+    latex_to_png(eqn, "tmp_eqn.png", verbose=False)