3 files changed, 20 insertions(+), 15 deletions(-)

M src/distfield.rs
M src/image.rs
M src/main.rs

@@ 1,39 1,40 @@
 //! Approximate solution based on distance fields.
 
-use std::f64::consts::{FRAC_1_SQRT_2, LN_2};
 use crate::math::compute_erf7;
 
 /// Generate a blurred rounded rectangle using distance field approximation.
-pub fn gen_distfield(width: usize, height: usize, w: f64, h: f64, r: f64, s: f64, r_mul: f64, exponent: f64) -> Vec<u8> {
-    // Try to calculate parameters
-    let r_orig = r;
+pub fn gen_distfield(width: usize, height: usize, w: f64, h: f64, r: f64, s: f64) -> Vec<u8> {
+    // To avoid divide by 0; potentially should be a bigger number for antialiasing.
+    let s = s.max(1e-6);
 
     let min_edge = w.min(h);
     let rmax = 0.5 * min_edge;
     let r0 = r.hypot(s * 1.15).min(rmax);
     let r1 = r.hypot(s * 2.0).min(rmax);
 
-    //let exponent = (-LN_2) / (1.0 - (1.0 - FRAC_1_SQRT_2) * r0 / r1).ln();
-    //let exponent = 6.0 * r1 / r0 - 4.0;
     let exponent = 2.0 * r1 / r0;
-    println!("r1/r {}, exponent {}", r1 / r, exponent);
-    let r = r1;
 
     let s_inv = s.max(1e-6).recip();
+
+    // Pull in long end (make less eccentric).
+    let delta = 1.25 * s * ((-(0.5 * s_inv * w).powi(2)).exp() - (-(0.5 * s_inv * h).powi(2)).exp());
+    let w = w + delta.min(0.0);
+    let h = h - delta.max(0.0);
+
     let recip_exponent = exponent.recip();
     let mut buf = vec![0u8; width * height];
-    let scale = 0.5 * compute_erf7(s_inv * 0.5 * (w.max(h) - 0.5 * r_orig));
+    let scale = 0.5 * compute_erf7(s_inv * 0.5 * (w.max(h) - 0.5 * r));
     for j in 0..height {
         let y = (j as f64) + 0.5 - 0.5 * (height as f64);
-        let y0 = y.abs() - (h * 0.5 - r);
+        let y0 = y.abs() - (h * 0.5 - r1);
         let y1 = y0.max(0.0);
         for i in 0..width {
             let x = (i as f64) + 0.5 - 0.5 * (width as f64);
-            let x0 = x.abs() - (w * 0.5 - r);
+            let x0 = x.abs() - (w * 0.5 - r1);
             let x1 = x0.max(0.0);
             let d_pos = (x1.powf(exponent) + y1.powf(exponent)).powf(recip_exponent);
             let d_neg = x0.max(y0).min(0.0);
-            let d = d_pos + d_neg - r;
+            let d = d_pos + d_neg - r1;
             let z = scale * (compute_erf7(s_inv * (min_edge + d)) - compute_erf7(s_inv * d));
             buf[j * width + i] = (z * 255.0).round() as u8;
         }

@@ 14,7 14,7 @@ pub fn make_image_one(ctx: &mut PaintCtx, w: usize, h: usize, data: &[u8]) -> Im
     ctx.make_image(w, h, &buf, ImageFormat::RgbaPremul).unwrap()
 }
 
-const N_STEPS: f64 = 255.0;
+const N_STEPS: f64 = 6.0;
 
 fn quantize(b: u8) -> u8 {
     ((b as f64 * (N_STEPS / 255.0)).round() * (255.0 / N_STEPS)).round() as u8

@@ 15,9 15,11 @@ struct AppState {
     radius: f64,
     std_dev: f64,
 
+    /*
     // extra parameters for distance field renderer
     r_mul: f64,
     exponent: f64,
+    */
 }
 
 struct BlurWidget;


@@ 59,8 61,6 @@ impl Widget<AppState> for BlurWidget {
             data.height,
             radius,
             data.std_dev,
-            data.r_mul,
-            data.exponent,
         );
         let d1 = integration::gen_integrate(
             IM_WIDTH,


@@ 88,10 88,12 @@ fn ui_builder() -> impl Widget<AppState> {
         .with_child(Slider::new().with_range(0.0, 50.0).lens(AppState::radius))
         .with_spacer(5.0)
         .with_child(Slider::new().with_range(0.0, 50.0).lens(AppState::std_dev))
+        /*
         .with_spacer(5.0)
         .with_child(Slider::new().with_range(1.0, 5.0).lens(AppState::r_mul))
         .with_spacer(5.0)
         .with_child(Slider::new().with_range(2.0, 10.0).lens(AppState::exponent))
+        */
         .with_spacer(5.0)
         .with_flex_child(BlurWidget, 1.0)
 }


@@ 103,8 105,10 @@ fn main() {
         radius: 5.0,
         std_dev: 5.0,
 
+        /*
         r_mul: 1.0,
         exponent: 2.0,
+        */
     };
     let main_window = WindowDesc::new(ui_builder).title(LocalizedString::new("blur toy"));
     AppLauncher::with_window(main_window).launch(data).unwrap();