Fixed 'magnify' shader in qmlvideofx example

Previous shader caused untransformed pixels (those outside of the lens)
radius to be offset slightly from their original positions.

Change-Id: I4df847fdc40073a55da8777981c3fdd373937658
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/examples/video/qmlvideofx/shaders/magnify.fsh b/examples/video/qmlvideofx/shaders/magnify.fsh
index c4c25d9e0..076db1799 100644
--- a/examples/video/qmlvideofx/shaders/magnify.fsh
+++ b/examples/video/qmlvideofx/shaders/magnify.fsh
@@ -53,13 +53,16 @@ uniform float posY;
 
 void main()
 {
-    float h = diffractionIndex * 0.5 * radius;
-    vec2 targetSize = vec2(targetWidth, targetHeight);
+    vec2 tc = qt_TexCoord0;
     vec2 center = vec2(posX, posY);
     vec2 xy = gl_FragCoord.xy - center.xy;
     float r = sqrt(xy.x * xy.x + xy.y * xy.y);
-    vec2 new_xy = r < radius ? xy * (radius - h) / sqrt(radius * radius - r * r) : xy;
-    vec2 tc = (new_xy + center) / targetSize;
-    tc.y = 1.0 - tc.y;
+    if (r < radius) {
+        float h = diffractionIndex * 0.5 * radius;
+        vec2 new_xy = r < radius ? xy * (radius - h) / sqrt(radius * radius - r * r) : xy;
+        vec2 targetSize = vec2(targetWidth, targetHeight);
+        tc = (new_xy + center) / targetSize;
+        tc.y = 1.0 - tc.y;
+    }
     gl_FragColor = qt_Opacity * texture2D(source, tc);
 }