[librsvg: 38/53] Convert the result of ImageSurface::create_from_png() to ARGB

[Federico Mena Quintero <federico src gnome org>]

commit a6b927fd96da8a659cafcf09438306665ca1fc67
Author: Federico Mena Quintero <federico gnome org>
Date:   Wed Oct 21 19:32:36 2020 -0500

    Convert the result of ImageSurface::create_from_png() to ARGB
    
    It may come out as Rgb24, who knew...

 tests/src/reference.rs | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)
---
diff --git a/tests/src/reference.rs b/tests/src/reference.rs
index 8c25f173..01e2474f 100644
--- a/tests/src/reference.rs
+++ b/tests/src/reference.rs
@@ -250,18 +250,37 @@ mod duplicated_from_librsvg_crate {
         path
     }
 
+    // FIXME: proper errors?
+    fn load_png_as_argb(path: &PathBuf) -> Result<cairo::ImageSurface, ()> {
+        let file = File::open(path).map_err(|_| ())?;
+
+        let mut reference_file = BufReader::new(file);
+
+        let png = cairo::ImageSurface::create_from_png(&mut reference_file).map_err(|_| ())?;
+        let argb = cairo::ImageSurface::create(
+            cairo::Format::ARgb32,
+            png.get_width(),
+            png.get_height(),
+        ).map_err(|_| ())?;
+
+        {
+            // convert to ARGB; the PNG may come as Rgb24
+            let cr = cairo::Context::new(&argb);
+            cr.set_source_surface(&png, 0.0, 0.0);
+            cr.paint();
+        }
+
+        Ok(argb)
+    }
+
     // FIXME: this is slightly different from librsvg_crate
     pub fn compare_to_file(
         output_surf: &SharedImageSurface,
         output_base_name: &str,
         reference_path: &PathBuf,
     ) {
-        let file = File::open(reference_path).unwrap();
-
-        let mut reference_file = BufReader::new(file);
-
-        let reference = cairo::ImageSurface::create_from_png(&mut reference_file).unwrap();
-        let reference_surf = SharedImageSurface::wrap(reference, SurfaceType::SRgb).unwrap();
+        let png = load_png_as_argb(reference_path).unwrap();
+        let reference_surf = SharedImageSurface::wrap(png, SurfaceType::SRgb).unwrap();
 
         compare_to_surface(output_surf, &reference_surf, output_base_name);
     }