[librsvg: 10/12] Use 32 bit floating point for Pixel::unpremultiply()

[Federico Mena Quintero <federico src gnome org>]

commit 184046914659b4b0b151d1ce49d620370a932eec
Author: Sven Neumann <sven svenfoo org>
Date:   Tue Oct 13 13:18:41 2020 +0200

    Use 32 bit floating point for Pixel::unpremultiply()
    
    This is slightly faster, at least on my machine.

 librsvg/pixbuf_utils.rs                 | 1 +
 rsvg_internals/src/surface_utils/mod.rs | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/librsvg/pixbuf_utils.rs b/librsvg/pixbuf_utils.rs
index 53e1406b..ebb92734 100644
--- a/librsvg/pixbuf_utils.rs
+++ b/librsvg/pixbuf_utils.rs
@@ -51,6 +51,7 @@ pub fn pixbuf_from_surface(surface: &SharedImageSurface) -> Result<Pixbuf, Rende
 
     for (src_row, dest_row) in surface.rows().zip(pixbuf_rows) {
         let row: &mut [Pixel] = dest_row.as_rgba_mut();
+
         for (src, dest) in src_row.iter().zip(row.iter_mut()) {
             *dest = if src.a == 0 {
                 Pixel::default()
diff --git a/rsvg_internals/src/surface_utils/mod.rs b/rsvg_internals/src/surface_utils/mod.rs
index c4e2182b..7fb35984 100644
--- a/rsvg_internals/src/surface_utils/mod.rs
+++ b/rsvg_internals/src/surface_utils/mod.rs
@@ -87,8 +87,8 @@ impl PixelOps for Pixel {
         if self.a == 0 {
             self
         } else {
-            let alpha = f64::from(self.a) / 255.0;
-            self.map_rgb(|x| ((f64::from(x) / alpha) + 0.5) as u8)
+            let alpha = f32::from(self.a) / 255.0;
+            self.map_rgb(|x| ((f32::from(x) / alpha) + 0.5) as u8)
         }
     }