Grey threshold
A simple shader that compares average pixel color with threshold and outputs shifted color in different directions depending on the delta parameter
The demo scene is provided by awesome Jaanus Jaggo (Perfoon).
Shader code
shader_type canvas_item;
uniform sampler2D SCREEN_TEXTURE : hint_screen_texture, filter_linear_mipmap;
uniform float threshold: hint_range(0.0,1.0) = 0.5;
uniform float delta: hint_range(0.0,1.0) = 0.2;
void fragment(){
vec4 screen_color = texture(SCREEN_TEXTURE, SCREEN_UV); // Get the color from the screen texture
float avg = (screen_color.r + screen_color.g + screen_color.b) / 3.0;
if (avg< threshold){
COLOR.rgb = vec3(screen_color.r - delta, screen_color.r - delta, screen_color.r - delta);
}else{
COLOR.rgb = vec3(screen_color.r + delta, screen_color.r + delta, screen_color.r + delta);
}
}