Vignette effect to screen

res/shaders/screen.glslf

@@ -2,8 +2,29 @@ in vec2 v_coord;
 out vec4 f_color;
 
 uniform sampler2D u_texture0;
+uniform ivec2 u_screenSize;
+
+float random(vec2 st){
+    return fract(sin(dot(st.xy ,vec2(12.9898,78.233))) * 43758.5453);
+}
+
+// Vignette
+vec4 apply_vignette(vec4 color)
+{
+    vec2 position = (gl_FragCoord.xy / u_screenSize) - vec2(0.5);
+    float dist = length(position);
+
+    float radius = 0.88;
+    float softness = 0.365;
+    float vignette = smoothstep(radius, radius - softness, dist);
+
+    color.rgb = color.rgb - (1.0 - vignette);
+
+    return color;
+}
 
 void main(){
 	f_color = texture(u_texture0, v_coord);
+	f_color = apply_vignette(f_color);
 }