[librsvg/attribute-parsers-737: 15/26] feColorMatrix: Update coefficients for luminanceToAlpha per the Filter Effects Module Level 1 spec

[Federico Mena Quintero <federico src gnome org>]

commit 90c07e62092038e0e8a8b4c7f35131870fdcfe90
Author: Federico Mena Quintero <federico gnome org>
Date:   Thu Oct 20 16:59:53 2022 -0500

    feColorMatrix: Update coefficients for luminanceToAlpha per the Filter Effects Module Level 1 spec
    
    Old values from SVG 1.1: https://www.w3.org/TR/SVG11/filters.html#feColorMatrixElement
    
    New values: https://drafts.fxtf.org/filter-effects/#element-attrdef-fecolormatrix-values

 src/filters/color_matrix.rs | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)
---
diff --git a/src/filters/color_matrix.rs b/src/filters/color_matrix.rs
index 8b4f469b9..9376cec4a 100644
--- a/src/filters/color_matrix.rs
+++ b/src/filters/color_matrix.rs
@@ -79,15 +79,7 @@ impl SetAttributes for FeColorMatrix {
         // Now read the matrix correspondingly.
         // LuminanceToAlpha doesn't accept any matrix.
         if operation_type == OperationType::LuminanceToAlpha {
-            self.params.matrix = {
-                Matrix5::new(
-                    0.0,    0.0,    0.0,    0.0, 0.0,
-                    0.0,    0.0,    0.0,    0.0, 0.0,
-                    0.0,    0.0,    0.0,    0.0, 0.0,
-                    0.2125, 0.7154, 0.0721, 0.0, 0.0,
-                    0.0,    0.0,    0.0,    0.0, 1.0,
-                )
-            };
+            self.params.matrix = ColorMatrix::luminance_to_alpha_matrix();
         } else {
             for (attr, value) in attrs
                 .iter()
@@ -214,6 +206,18 @@ impl ColorMatrix {
         matrix[(4, 4)] = 1.0;
         matrix
     }
+
+    // https://drafts.fxtf.org/filter-effects/#element-attrdef-fecolormatrix-values
+    #[rustfmt::skip]
+    fn luminance_to_alpha_matrix() -> Matrix5<f64> {
+        Matrix5::new(
+            0.0,    0.0,    0.0,    0.0, 0.0,
+            0.0,    0.0,    0.0,    0.0, 0.0,
+            0.0,    0.0,    0.0,    0.0, 0.0,
+            0.2126, 0.7152, 0.0722, 0.0, 0.0,
+            0.0,    0.0,    0.0,    0.0, 1.0,
+        )
+    }
 }
 
 impl FilterEffect for FeColorMatrix {