Constant SHARPEN

const SHARPEN: &str = r#"
void main() {
    vec2 uv = gl_FragCoord.xy / u_res;
    vec4 src = texture(tex, uv);
    vec2 o = vec2(max(p1, 0.5) * u_scale) / u_res;
    vec3 b = texture(tex, uv + vec2(-o.x, -o.y)).rgb + texture(tex, uv + vec2(0.0, -o.y)).rgb
           + texture(tex, uv + vec2(o.x, -o.y)).rgb + texture(tex, uv + vec2(-o.x, 0.0)).rgb
           + src.rgb + texture(tex, uv + vec2(o.x, 0.0)).rgb
           + texture(tex, uv + vec2(-o.x, o.y)).rgb + texture(tex, uv + vec2(0.0, o.y)).rgb
           + texture(tex, uv + vec2(o.x, o.y)).rgb;
    vec4 res = vec4(clamp(src.rgb + max(p0, 0.0) * (src.rgb - b / 9.0), 0.0, 1.0), src.a);
    float m = u_has_mask > 0.5 ? texture(u_mask, uv).r : 1.0;
    out_color = mix(src, res, m);
}
"#;

Unsharp mask against a 3x3 box at p1 project px spacing.