add poc blender preview

Author: inkhey

preview.py

@@ -0,0 +1,63 @@
+import subprocess
+from abc import ABC
+
+import typing
+from enum import Enum
+
+from preview_generator.preview.generic_preview import ImagePreviewBuilder
+from preview_generator.utils import MimetypeMapping, ImgDims
+
+class BlenderEngine(str, Enum):
+    WORKBENCH_ENGINE = "BLENDER_WORKBENCH" # The fastest, don't render much (no texture, etc,…)
+    EEVE_ENGINE = "BLENDER_EEVEE" # fastest real render, videogame-like render.
+    CYCLE_ENGINE = "CYCLES" # Raytracing engine, very slow !
+
+class ImagePreviewBuilderBlender(ImagePreviewBuilder):
+    weight: int = 150
+    engine: BlenderEngine = BlenderEngine.WORKBENCH_ENGINE
+    thread_number: int = 4
+
+    @classmethod
+    def get_label(cls) -> str:
+        return "Blender Preview Builder"
+
+    @classmethod
+    def get_supported_mimetypes(cls) -> typing.List[str]:
+        return ['application/x-blender']
+
+    @classmethod
+    def get_mimetypes_mapping(cls) -> typing.List[MimetypeMapping]:
+        return [MimetypeMapping("application/x-blender", ".blend")]
+
+
+    @classmethod
+    def check_dependencies(cls) -> None:
+        #TODO - check bpy exist.
+        pass
+
+    def build_jpeg_preview(
+        self,
+        file_path: str,
+        preview_name: str,
+        cache_path: str,
+        page_id: int,
+        extension: str = ".jpeg",
+        size: ImgDims = None,
+        mimetype: str = "",
+    ) -> None:
+        if not size:
+            size = self.default_size
+        preview_file_path = "{path}".format(
+            path=cache_path + preview_name, extension=extension, page_id="####"
+        )
+        # TODO : use bpy instead to:
+        # - set the render size
+        # - get the frame number
+        # - give proper name to preview
+        # I didn't do it now, as bpy doesn't run on my debian unstable (hard to troubleshoot).
+        command = ["blender", "-b", file_path, "-o", preview_file_path, "-E", self.engine, "-t", str(self.thread_number), "-f", str(page_id+1), "-F", "JPEG"]
+        subprocess.check_call(
+            command,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.STDOUT,
+        )