Add export function 'generate_pic()'

lokrez/export.py

@@ -1,3 +1,4 @@
+import io
 import os
 import subprocess
 import tempfile
@@ -146,3 +147,126 @@ def generate_outfile(
                         )
                     )
     return None
+
+# =============================================================================
+def generate_pic(
+        templatesdir,
+        templatename,
+        context,
+        outform="svg",
+        log = None,
+        cachedir = None,
+        ):
+
+    if outform not in ["svg", "png"]:
+        raise ValueError("unsupported output format '{}'".format(outform))
+
+    # Template rendering
+    # -------------------------------------------------------------------------
+    log.info("Generating SVG using '{}' template".format(templatename))
+    log.debug("Context : {}".format(context))
+
+    log.debug(
+            "Initializing jinja2 with template dir '{}'" \
+                    .format(templatesdir)
+                    )
+    jj2_env = jinja2.Environment(
+            loader = jinja2.FileSystemLoader(
+                str(templatesdir),
+                )
+            )
+
+    try:
+        jj2_tpl = jj2_env.get_template(
+                # Jinja specific path format
+                "{}/template.svg.j2".format(templatename),
+                )
+    except jinja2.exceptions.TemplateNotFound as e:
+        raise e
+    except Exception as e:
+        log.error("Could not find template '{}'".format(templatename))
+        log.debug(e, exc_info=1)
+        return None
+
+    # To SVG
+    # -------------------------------------------------------------------------
+    if outform == "svg":
+        return jj2_tpl.render(context)
+
+    # To PNG with inkscape
+    # -------------------------------------------------------------------------
+    if outform == "png":
+
+        if cachedir is None:
+            cachedir_tmp = tempfile.TemporaryDirectory()
+            cachedir = cachedir_tmp.name
+        else:
+            cachedir.mkdir(parents=True, exist_ok=True)
+
+        tmpsvg = tempfile.NamedTemporaryFile(
+                suffix=".svg",
+                mode = "w",
+                delete = False,
+                dir = str(cachedir),
+                )
+        tmpsvg.close()
+        tmppng = tempfile.NamedTemporaryFile(
+                suffix = ".png",
+                mode = "w",
+                delete = False,
+                dir = str(cachedir),
+                )
+        tmppng.close()
+        try:
+            log.info(
+                    "Exporting to {} using inkscape" \
+                            .format(outform),
+                            )
+            import subprocess
+
+            jj2_tpl.stream(context).dump( tmpsvg.name )
+
+            inkscape_process = subprocess.Popen(
+                    [
+                        "inkscape",
+                        tmpsvg.name,
+                        "--export-filename",
+                        tmppng.name,
+                        ],
+                    stdout = subprocess.PIPE,
+                    stderr = subprocess.STDOUT,
+                    universal_newlines = True,
+                    )
+
+            for line_out in iter(inkscape_process.stdout.readline, ""):
+                log.debug(line_out)
+
+            inkscape_process.stdout.close()
+
+            rv = inkscape_process.wait()
+
+            if rv != 0:
+                raise Exception(
+                        "Bad inkscape return code '{}'" \
+                                .format(inkscape_process.returncode)
+                                )
+
+            with open(tmppng.name, "rb") as fh:
+                buf = io.BytesIO(fh.read())
+
+            return buf
+
+        except Exception as e:
+            log.warning("Failed to export with inkscape")
+            log.debug(e, exc_info=True)
+
+        finally:
+            os.unlink(tmpsvg.name)
+            os.unlink(tmppng.name)
+
+            try:
+                cachedir_tmp.cleanup()
+            except:
+                pass
+
+        return None