tests: add fast gaussian blur test

The test tolerance is set to 5% to allow OpenGL/Vulkan software implementations
to pass.

tests/blur.py

@@ -44,3 +44,25 @@ def blur_gaussian(cfg: ngl.SceneCfg):
         ),
     )
     return ngl.Group(children=(blur, ngl.RenderTexture(blurred_texture)))
+
+
+@test_fingerprint(keyframes=10, tolerance=5)
+@ngl.scene()
+def blur_fast_gaussian(cfg: ngl.SceneCfg):
+    cfg.aspect_ratio = (1, 1)
+    cfg.duration = 10
+
+    noise = ngl.RenderNoise(type="blocky", octaves=3, scale=(9, 9))
+    noise_texture = ngl.Texture2D(data_src=noise)
+    blurred_texture = ngl.Texture2D()
+    blur = ngl.FastGaussianBlur(
+        source=noise_texture,
+        destination=blurred_texture,
+        bluriness=ngl.AnimatedFloat(
+            [
+                ngl.AnimKeyFrameFloat(0, 0),
+                ngl.AnimKeyFrameFloat(cfg.duration, 1),
+            ]
+        ),
+    )
+    return ngl.Group(children=(blur, ngl.RenderTexture(blurred_texture)))

tests/meson.build

@@ -88,6 +88,7 @@ foreach backend : backends
 
   tests_blur = [
     'gaussian',
+    'fast_gaussian',
   ]
 
   tests_color = [

tests/refs/blur_fast_gaussian.ref

@@ -0,0 +1,10 @@
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