SpritePalettizer godot shader example

shader_type canvas_item;                    //2D shader
render_mode unshaded, blend_disabled;       // no bells and wistles
uniform sampler2D palette;                  //Use palletes in collum with colors in rows
uniform float palette_count = 1.0;          //Tells the shader how many palettes you have
uniform float palette_index = 0.0;          //Telss the shader which palette to choose

void fragment(){
    float increment = 1.0/palette_count;                    //Value for getting palette index
    float y = increment * palette_index + increment * 0.5;  // + safety measure for floating point imprecision
    vec4 color = texture(TEXTURE, UV);                      //Original graysscale color used as collumn index
    vec4 new_collor = texture(palette, vec2(color.r, y));   //get color from palette texture
    float a = step(0.00392, color.a);                       //check if transparent color is less than 1/255 for backgrounds
    new_color.a *= a;                                       //if BG is transparent, then alpha is multiplied by 0

    COLOR = new_color;                                      //set new color from palette
}