Adding basic palette-switching example using uniform arrays.

examples/shaders/resources/shaders/glsl100/palette-switch.fs

@@ -0,0 +1,29 @@
+#version 100
+
+precision mediump float;
+
+const int colors = 8;
+
+// Input vertex attributes (from vertex shader)
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform ivec3 palette[colors];
+
+void main()
+{
+    // Texel color fetching from texture sampler
+    vec4 texelColor = texture(texture0, fragTexCoord) * fragColor;
+
+    // Convert the (normalized) texel color RED component (GB would work, too)
+    // to the palette index by scaling up from [0, 1] to [0, 255].
+    int index = int(texelColor.r * 255.0);
+    ivec3 color = palette[index];
+
+    // Calculate final fragment color. Note that the palette color components
+    // are defined in the range [0, 255] and need to be normalized to [0, 1]
+    // for OpenGL to work.
+    gl_FragColor = vec4(color / 255.0, texelColor.a);
+}