Port hardsubx imgops (CCExtractor#1439)

* add hardsubx rust module and expose it

* port rgb_to_hsv to rust

* add dependency fast-math and extern it

* port rgb_to_lab to rust

also make preprocessor to not allow compilation of hardsubx_imgops
if WITHOUT_RUST is OFF

* improve if-else constructs for readability

* unroll  macros that were only used once and remove their definition

* Improve readability of rgb_to_lab function (and fixes)

The function in Rust behaves slightly differently than its C counterpart

* remove fast math library, use palette library and rewrite imgops using it

* run formatter

* replace destructuring assignment statement with normal assignment statements because of build rust compiler issues

* run formatter on C code for imgops

* remove extern for modules because it is not required

* improve comment placement in rust imgops

Co-authored-by: Punit Lodha <[email protected]>

src/lib_ccx/hardsubx_imgops.c

@@ -1,8 +1,8 @@
 #include "lib_ccx.h"
 #include "utility.h"
 
-#ifdef ENABLE_HARDSUBX
-//TODO: Correct FFMpeg integration
+#if defined(ENABLE_HARDSUBX) && defined(DISABLE_RUST)
+// TODO: Correct FFMpeg integration
 #include <libavcodec/avcodec.h>
 #include <libavformat/avformat.h>
 #include <libavutil/imgutils.h>
@@ -18,7 +18,7 @@
 
 void rgb_to_hsv(float R, float G, float B, float *H, float *S, float *V)
 {
-	//Conversion into HSV color space to get Hue
+	// Conversion into HSV color space to get Hue
 	float r = R / 255.0f;
 	float g = G / 255.0f;
 	float b = B / 255.0f;
@@ -68,7 +68,7 @@ void rgb_to_hsv(float R, float G, float B, float *H, float *S, float *V)
 
 void rgb_to_lab(float R, float G, float B, float *L, float *a, float *b)
 {
-	//Conversion to the CIE-LAB color space to get the Luminance
+	// Conversion to the CIE-LAB color space to get the Luminance
 	float X, Y, Z, fX, fY, fZ;
 
 	X = 0.412453 * R + 0.357580 * G + 0.180423 * B;

src/rust/Cargo.toml

@@ -14,6 +14,7 @@ crate-type = ["staticlib"]
 log = "0.4.0"
 env_logger = "0.8.4"
 iconv = "0.1.1"
+palette = "0.6.0"
 
 [build-dependencies]
 bindgen = "0.58.1"

src/rust/src/hardsubx/imgops.rs

@@ -0,0 +1,24 @@
+use palette::{FromColor, Hsv, Lab, Srgb};
+
+#[no_mangle]
+pub extern "C" fn rgb_to_hsv(R: f32, G: f32, B: f32, H: &mut f32, S: &mut f32, V: &mut f32) {
+    let rgb = Srgb::new(R, G, B);
+
+    let hsv_rep = Hsv::from_color(rgb);
+
+    *H = hsv_rep.hue.to_positive_degrees();
+    *S = hsv_rep.saturation;
+    *V = hsv_rep.value;
+}
+
+#[no_mangle]
+pub extern "C" fn rgb_to_lab(R: f32, G: f32, B: f32, L: &mut f32, a: &mut f32, b: &mut f32) {
+    let rgb = Srgb::new(R, G, B);
+
+    // This declaration sets the white-point as per the D65 standard
+    let lab_rep = Lab::<palette::white_point::D65, f32>::from_color(rgb);
+
+    *L = lab_rep.l;
+    *a = lab_rep.a;
+    *b = lab_rep.b;
+}

src/rust/src/hardsubx/mod.rs

@@ -0,0 +1 @@
+pub mod imgops;

src/rust/src/lib.rs

@@ -13,6 +13,7 @@ pub mod bindings {
     include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
 }
 pub mod decoder;
+pub mod hardsubx;
 pub mod utils;
 
 #[cfg(windows)]