update Shaders

- fix ripple effect
- fix flip effect

forge-gui-mobile-dev/shaders/grayscale.frag

@@ -6,10 +6,11 @@ varying vec4 v_color;
 varying vec2 v_texCoords;
 uniform sampler2D u_texture;
 uniform float u_grayness;
+uniform float u_bias;
 
 void main() {
   vec4 c = v_color * texture2D(u_texture, v_texCoords);
   float grey = dot( c.rgb, vec3(0.22, 0.707, 0.071) );
   vec3 blendedColor = mix(c.rgb, vec3(grey), u_grayness);
-  gl_FragColor = vec4(blendedColor.rgb, c.a);
+  gl_FragColor = mix(vec4(0.0, 0.0, 0.0, 1.0), vec4(blendedColor.rgb, c.a), u_bias);
 }