[gegl] panorma-projection: improve inverse

[Øyvind Kolås <ok src gnome org>]

commit 5014211178959076b134bd74a89b087f9bbcd8d1
Author: Øyvind Kolås <pippin gimp org>
Date:   Mon Apr 9 14:54:28 2018 +0200

    panorma-projection: improve inverse
    
    Renamed 'reverse' property to 'inverse', excluded some mapped pixels that were
    bleeding in from behind the observer when doing inverse. Avoid using lohalo or
    nohalo samplers for reverse transform, as well as other small code cleanups.

 operations/common/panorama-projection.c |   70 ++++++++++++++-----------------
 1 files changed, 31 insertions(+), 39 deletions(-)
---
diff --git a/operations/common/panorama-projection.c b/operations/common/panorama-projection.c
index 13ab7ab..51732aa 100644
--- a/operations/common/panorama-projection.c
+++ b/operations/common/panorama-projection.c
@@ -52,7 +52,7 @@ property_int    (height, _("Height"), -1)
   ui_meta       ("role", "output-extent")
   ui_meta       ("axis", "y")
 
-property_boolean(reverse, _("Inverse tranform"), FALSE)
+property_boolean(inverse, _("Inverse tranform"), FALSE)
   description   (_("Do the inverse mapping, useful for touching up zenith, nadir or other parts of 
panorama."))
 
 property_boolean(little_planet, _("Little planet"), FALSE)
@@ -88,8 +88,7 @@ struct _Transform
   float xoffset;
   float width;
   float height;
-  void (*xy2ll) (Transform *transform, float x, float  y, float *lon, float *lat);
-  void (*ll2xy) (Transform *transform, float lon, float  lat, float *x, float *y);
+  void (*mapfun) (Transform *transform, float x, float  y, float *lon, float *lat);
   int   reverse;
   int   do_spin;
   int   do_zoom;
@@ -175,7 +174,7 @@ gnomonic_ll2xy (Transform *transform,
   *x += transform->xoffset;
   *y += 0.5f;
 
-  if (cos_c <= 0)
+  if (cos_c <= 0.01)
   {
     *x = -.1;
     *y = -.1;
@@ -275,8 +274,21 @@ static void prepare_transform (Transform *transform,
                                int inverse)
 {
   float xoffset = 0.5;
-  transform->xy2ll = gnomonic_xy2ll;
-  transform->ll2xy = gnomonic_ll2xy;
+  transform->reverse = inverse;
+  if (little_planet)
+  {
+    if (inverse)
+      transform->mapfun = stereographic_ll2xy;
+    else
+      transform->mapfun = stereographic_xy2ll;
+  }
+  else
+  {
+    if (inverse)
+      transform->mapfun = gnomonic_ll2xy;
+    else
+      transform->mapfun = gnomonic_xy2ll;
+  }
 
   pan  = pan / 360 * M_PI * 2;
   spin = spin / 360 * M_PI * 2;
@@ -299,19 +311,6 @@ static void prepare_transform (Transform *transform,
     xoffset = ((orig_width - height)/height) / 2 + 0.5;
   }
 
-  if (little_planet)
-  {
-    transform->xy2ll = stereographic_xy2ll;
-    transform->ll2xy = stereographic_ll2xy;
-  }
-
-  if (inverse)
-  {
-    void (*temp) (Transform *transform, float x, float  y, float *lon, float *lat) = transform->xy2ll;
-    transform->xy2ll = transform->ll2xy;
-    transform->ll2xy = temp;
-  }
-  transform->reverse = inverse;
 
 
   transform->do_spin = fabs (spin) > 0.000001 ? 1 : 0;
@@ -381,7 +380,7 @@ static void prepare_transform2 (Transform *transform,
                      o->pan, o->spin, o->zoom, o->tilt,
                      o->little_planet, o->width / factor, o->height / factor,
                      in_rect.width, in_rect.height,
-                     o->reverse);
+                     o->inverse);
 
 }
 
@@ -418,23 +417,18 @@ process (GeglOperation       *operation,
   if (level)
     sampler_type = GEGL_SAMPLER_NEAREST;
 
-  if (sampler_type != GEGL_SAMPLER_NEAREST) /* we crash with any other samplers */
-    sampler_type = GEGL_SAMPLER_LINEAR;
-
-  format_io = babl_format ("RaGaBaA float");
+  if (transform.reverse)
   {
-    /* XXX: panorama projection needs to sample from a higher resolution than
-     * its output to yield good results. This affects which level should
-     * be rendered for source nodes..
-     */
+    /* the computed scale matrix seem wrong for these samplers */
+    if (sampler_type == GEGL_SAMPLER_NOHALO ||
+        sampler_type == GEGL_SAMPLER_LOHALO)
+      sampler_type = GEGL_SAMPLER_CUBIC;
+  }
 
-    gint sample_level = level - 3;
+  format_io = babl_format ("RaGaBaA float");
 
-    if (sample_level < 0)
-      sample_level = 0;
-    sampler = gegl_buffer_sampler_new_at_level (input, format_io, sampler_type,
-                                       sample_level);
-  }
+  sampler = gegl_buffer_sampler_new_at_level (input, format_io, sampler_type,
+                                              0);
 
   if (sampler_type != GEGL_SAMPLER_NEAREST)
     scale = &scale_matrix;
@@ -442,6 +436,7 @@ process (GeglOperation       *operation,
   {
     float   ud = ((1.0/(transform.reverse?in_rect.width:transform.width))*factor);
     float   vd = ((1.0/transform.height)*factor);
+    int abyss_mode = transform.reverse ? GEGL_ABYSS_NONE : GEGL_ABYSS_LOOP;
 
     it = gegl_buffer_iterator_new (output, result, level, format_io,
                                    GEGL_ACCESS_WRITE, GEGL_ABYSS_NONE);
@@ -457,9 +452,6 @@ process (GeglOperation       *operation,
         float   u, v;
 
         float *out = it->data[0];
-        int abyss_mode = GEGL_ABYSS_LOOP;
-        if (transform.reverse)
-          abyss_mode = GEGL_ABYSS_NONE;
 
         u = u0;
         v = ((y*factor * 1.0/in_rect.height));
@@ -471,7 +463,7 @@ process (GeglOperation       *operation,
                 float cx, cy;
 #define gegl_unmap(xx,yy,ud,vd) {                                       \
                   float rx, ry;                                         \
-                  transform.xy2ll (&transform, xx, yy, &rx, &ry);       \
+                  transform.mapfun (&transform, xx, yy, &rx, &ry);       \
                   ud = rx;vd = ry;}
                 gegl_sampler_compute_scale (scale_matrix, u, v);
                 gegl_unmap(u,v, cx, cy);
@@ -499,7 +491,7 @@ process (GeglOperation       *operation,
               {
                 float cx, cy;
 
-                transform.xy2ll (&transform, u, v, &cx, &cy);
+                transform.mapfun (&transform, u, v, &cx, &cy);
                 gegl_sampler_get (sampler,
                                   cx * (transform.reverse?transform.width:in_rect.width), cy * 
in_rect.height,
                                   scale, out, abyss_mode);