♻️ refactor: rustify writer utility get_zoom_factor (#316)

Author: SigureMo

packages/biliass/Cargo.lock

@@ -14,6 +14,7 @@ bytes = "1.7.1"
 prost = "0.13.2"
 thiserror = "1.0.63"
 quick-xml = "0.36.1"
+cached = "0.53.1"
 
 [build-dependencies]
 prost-build = "0.13.2"

packages/biliass/rust/Cargo.toml

@@ -28,5 +28,6 @@ fn biliass_pyo3(m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_function(wrap_pyfunction!(python::py_convert_timestamp, m)?)?;
     m.add_function(wrap_pyfunction!(python::py_ass_escape, m)?)?;
     m.add_function(wrap_pyfunction!(python::py_convert_color, m)?)?;
+    m.add_function(wrap_pyfunction!(python::py_get_zoom_factor, m)?)?;
     Ok(())
 }

packages/biliass/rust/src/lib.rs

@@ -6,4 +6,4 @@ mod writer;
 pub use comment::{PyComment, PyCommentPosition};
 pub use proto::{PyDanmakuElem, PyDmSegMobileReply};
 pub use reader::{py_read_comments_from_protobuf, py_read_comments_from_xml};
-pub use writer::{py_ass_escape, py_convert_color, py_convert_timestamp};
+pub use writer::{py_ass_escape, py_convert_color, py_convert_timestamp, py_get_zoom_factor};

packages/biliass/rust/src/python/mod.rs

@@ -17,3 +17,11 @@ pub fn py_ass_escape(text: &str) -> PyResult<String> {
 pub fn py_convert_color(rgb: u32, width: u32, height: u32) -> PyResult<String> {
     Ok(writer::utils::convert_color(rgb, Some(width), Some(height)))
 }
+
+#[pyfunction(name = "get_zoom_factor")]
+pub fn py_get_zoom_factor(
+    source_size: (u32, u32),
+    target_size: (u32, u32),
+) -> PyResult<(f32, f32, f32)> {
+    Ok(writer::utils::get_zoom_factor(source_size, target_size))
+}

packages/biliass/rust/src/python/writer.rs

@@ -1,3 +1,5 @@
+use cached::proc_macro::cached;
+
 fn divmod(a: f64, b: f64) -> (f64, f64) {
     (a / b, a % b)
 }
@@ -74,3 +76,30 @@ pub fn convert_color(rgb: u32, width: Option<u32>, height: Option<u32>) -> Strin
         )
     }
 }
+
+#[cached]
+pub fn get_zoom_factor(source_size: (u32, u32), target_size: (u32, u32)) -> (f32, f32, f32) {
+    let source_size = (source_size.0 as f32, source_size.1 as f32);
+    let target_size = (target_size.0 as f32, target_size.1 as f32);
+    let source_aspect = source_size.0 / source_size.1;
+    let target_aspect = target_size.0 / target_size.1;
+    if target_aspect < source_aspect {
+        // narrower
+        let scale_factor = target_size.0 / source_size.0;
+        (
+            scale_factor,
+            0.0,
+            (target_size.1 - target_size.0 / source_aspect) / 2.0,
+        )
+    } else if target_aspect > source_aspect {
+        // wider
+        let scale_factor = target_size.1 / source_size.1;
+        (
+            scale_factor,
+            (target_size.0 - target_size.1 * source_aspect) / 2.0,
+            0.0,
+        )
+    } else {
+        (target_size.0 / source_size.0, 0.0, 0.0)
+    }
+}

packages/biliass/rust/src/writer/utils.rs

@@ -59,4 +59,5 @@ def read_comments_from_xml(text: str, fontsize: float) -> list[Comment]: ...
 def read_comments_from_protobuf(data: bytes, fontsize: float) -> list[Comment]: ...
 def convert_timestamp(timestamp: float) -> float: ...
 def ass_escape(text: str) -> str: ...
-def convert_color(rgb: int, width: int = ..., height: int = ...): ...
+def convert_color(rgb: int, width: int = ..., height: int = ...) -> str: ...
+def get_zoom_factor(source_size: tuple[int, int], target_size: tuple[int, int]) -> tuple[float, float, float]: ...