spectra: shade better and extend outside by inpainting

src/pipe/modules/pick/display.comp

@@ -78,6 +78,9 @@ main()
     rgb = max(rgb, picked_rgb * vec3(pow(smoothstep(t, 0.0, d), 3)));
     // on white:
     // rgb = mix(rgb, picked_rgb, vec3(pow(smoothstep(t, 0.0, d), 3)));
+    // shade below:
+    if(ipos.y / float(imageSize(img_out).y) > 1.0-val)
+      rgb = mix(rgb, picked_rgb, 0.1);
   }
   imageStore(img_out, ipos, vec4(rgb, 1));
 }

src/tools/spec/mkspectra.c

@@ -88,9 +88,9 @@ void init_coeffs(double coeffs[3])
 void clamp_coeffs(double coeffs[3])
 {
   double max = fmax(fmax(fabs(coeffs[0]), fabs(coeffs[1])), fabs(coeffs[2]));
-  if (max > 1000) {
+  if (max > 100000.0) {
     for (int j = 0; j < 3; ++j)
-      coeffs[j] *= 1000 / max;
+      coeffs[j] *= 100000.0 / max;
   }
 }
 
@@ -342,7 +342,7 @@ void parallel_run(uint32_t item, void *data)
 
   int ii = (int)fmin(d->max_w - 1, fmax(0, x * d->max_w + 0.5));
   int jj = (int)fmin(d->max_h - 1, fmax(0, y * d->max_h + 0.5));
-  double m = fmax(0.05, 0.5*d->max_b[ii + d->max_w * jj]);
+  double m = fmax(0.01, 0.5*d->max_b[ii + d->max_w * jj]);
   double rgbm[3] = {rgb[0] * m, rgb[1] * m, rgb[2] * m};
   double resid = gauss_newton(rgbm, coeffs);
 
@@ -425,6 +425,15 @@ int main(int argc, char **argv)
   for(int k=0;k<res*res;k++)
     parallel_run(k, &par);
 #endif
+  {
+    dt_inpaint_buf_t inpaint_buf = {
+      .dat = (float *)out,
+      .wd  = res,
+      .ht  = res,
+      .cpp = 4,
+    };
+    dt_inpaint(&inpaint_buf);
+  }
 
   { // write spectra map: (x,y) |--> sigmoid coeffs + saturation
     header_t head = (header_t) {