Replace ChronoshiftPaletteEffect with a post-processing shader.

glsl/postprocess_chronoshift.frag

@@ -0,0 +1,31 @@
+#version {VERSION}
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+uniform float Blend;
+uniform sampler2D WorldTexture;
+
+#if __VERSION__ == 120
+uniform vec2 WorldTextureSize;
+#else
+out vec4 fragColor;
+#endif
+
+void main()
+{
+#if __VERSION__ == 120
+	vec4 c = texture2D(WorldTexture, gl_FragCoord.xy / WorldTextureSize);
+#else
+	vec4 c = texture(WorldTexture, gl_FragCoord.xy / textureSize(WorldTexture, 0));
+#endif
+
+	float lum = 0.5 * (min(c.r, min(c.g, c.b)) + max(c.r, max(c.g, c.b)));
+	c = vec4(lum, lum, lum, c.a) * Blend + c * (1.0 - Blend);
+
+	#if __VERSION__ == 120
+	gl_FragColor = c;
+	#else
+	fragColor = c;
+	#endif
+}