[gimp] app: add gimp_brush_transform_get_scale()

[Ell <ell src gnome org>]

commit 2dddf59dbf3285218131fe689f989f5799640825
Author: Ell <ell_se yahoo com>
Date:   Wed Feb 12 23:39:38 2020 +0200

    app: add gimp_brush_transform_get_scale()
    
    ... which converts a (scale, aspect_ratio) pair to a (scale_x,
    scale_y) pair.
    
    Change gimp_brush_transform_matrix() to take (scale_x, scale_y)
    parameters, instead of (scale, aspect_ratio), and change the rest
    of the code accordingly.

 app/core/gimpbrush-transform.cc | 57 ++++++++++++++++++++++++++---------------
 app/core/gimpbrush-transform.h  |  8 ++++--
 2 files changed, 43 insertions(+), 22 deletions(-)
---
diff --git a/app/core/gimpbrush-transform.cc b/app/core/gimpbrush-transform.cc
index 11f440f516..0a97fd61b4 100644
--- a/app/core/gimpbrush-transform.cc
+++ b/app/core/gimpbrush-transform.cc
@@ -74,11 +74,15 @@ gimp_brush_real_transform_size (GimpBrush *brush,
                                 gint      *height)
 {
   GimpMatrix3 matrix;
+  gdouble     scale_x, scale_y;
   gint        x, y;
 
+  gimp_brush_transform_get_scale (scale, aspect_ratio,
+                                  &scale_x, &scale_y);
+
   gimp_brush_transform_matrix (gimp_brush_get_width  (brush),
                                gimp_brush_get_height (brush),
-                               scale, aspect_ratio, angle, reflect, &matrix);
+                               scale_x, scale_y, angle, reflect, &matrix);
 
   gimp_brush_transform_bounding_box (brush, &matrix, &x, &y, width, height);
 }
@@ -121,6 +125,7 @@ gimp_brush_real_transform_mask (GimpBrush *brush,
   GimpTempBuf  *source;
   const guchar *src;
   GimpMatrix3   matrix;
+  gdouble       scale_x, scale_y;
   gint          src_width;
   gint          src_height;
   gint          src_width_minus_one;
@@ -174,13 +179,16 @@ gimp_brush_real_transform_mask (GimpBrush *brush,
    */
   const guint fraction_bitmask = pow(2, fraction_bits) - 1 ;
 
+  gimp_brush_transform_get_scale (scale, aspect_ratio,
+                                  &scale_x, &scale_y);
+
   source = gimp_brush_get_mask (brush);
 
   src_width  = gimp_brush_get_width  (brush);
   src_height = gimp_brush_get_height (brush);
 
   gimp_brush_transform_matrix (src_width, src_height,
-                               scale, aspect_ratio, angle, reflect, &matrix);
+                               scale_x, scale_y, angle, reflect, &matrix);
 
   if (gimp_matrix3_is_identity (&matrix) && hardness == 1.0)
     return gimp_temp_buf_copy (source);
@@ -202,7 +210,7 @@ gimp_brush_real_transform_mask (GimpBrush *brush,
       gint        unrotated_dest_height;
 
       gimp_brush_transform_matrix (src_width, src_height,
-                                   scale, aspect_ratio, 0.0, FALSE,
+                                   scale_x, scale_y, 0.0, FALSE,
                                    &unrotated_matrix);
 
       gimp_brush_transform_bounding_box (brush, &unrotated_matrix,
@@ -431,6 +439,7 @@ gimp_brush_real_transform_pixmap (GimpBrush *brush,
   GimpTempBuf  *source;
   const guchar *src;
   GimpMatrix3   matrix;
+  gdouble       scale_x, scale_y;
   gint          src_width;
   gint          src_height;
   gint          src_width_minus_one;
@@ -484,13 +493,16 @@ gimp_brush_real_transform_pixmap (GimpBrush *brush,
    */
   const guint fraction_bitmask = pow(2, fraction_bits) - 1 ;
 
+  gimp_brush_transform_get_scale (scale, aspect_ratio,
+                                  &scale_x, &scale_y);
+
   source = gimp_brush_get_pixmap (brush);
 
   src_width  = gimp_brush_get_width  (brush);
   src_height = gimp_brush_get_height (brush);
 
   gimp_brush_transform_matrix (src_width, src_height,
-                               scale, aspect_ratio, angle, reflect, &matrix);
+                               scale_x, scale_y, angle, reflect, &matrix);
 
   if (gimp_matrix3_is_identity (&matrix) && hardness == 1.0)
     return gimp_temp_buf_copy (source);
@@ -512,7 +524,7 @@ gimp_brush_real_transform_pixmap (GimpBrush *brush,
       gint        unrotated_dest_height;
 
       gimp_brush_transform_matrix (src_width, src_height,
-                                   scale, aspect_ratio, 0.0, FALSE,
+                                   scale_x, scale_y, 0.0, FALSE,
                                    &unrotated_matrix);
 
       gimp_brush_transform_bounding_box (brush, &unrotated_matrix,
@@ -713,30 +725,35 @@ gimp_brush_real_transform_pixmap (GimpBrush *brush,
   return result;
 }
 
+void
+gimp_brush_transform_get_scale (gdouble  scale,
+                                gdouble  aspect_ratio,
+                                gdouble *scale_x,
+                                gdouble *scale_y)
+{
+  if (aspect_ratio < 0.0)
+    {
+      *scale_x = scale * (1.0 + (aspect_ratio / 20.0));
+      *scale_y = scale;
+    }
+  else
+    {
+      *scale_x = scale;
+      *scale_y = scale * (1.0 - (aspect_ratio / 20.0));
+    }
+}
+
 void
 gimp_brush_transform_matrix (gdouble      width,
                              gdouble      height,
-                             gdouble      scale,
-                             gdouble      aspect_ratio,
+                             gdouble      scale_x,
+                             gdouble      scale_y,
                              gdouble      angle,
                              gboolean     reflect,
                              GimpMatrix3 *matrix)
 {
   const gdouble center_x = width  / 2;
   const gdouble center_y = height / 2;
-  gdouble       scale_x  = scale;
-  gdouble       scale_y  = scale;
-
-  if (aspect_ratio < 0.0)
-    {
-      scale_x = scale * (1.0 - (fabs (aspect_ratio) / 20.0));
-      scale_y = scale;
-    }
-  else if (aspect_ratio > 0.0)
-    {
-      scale_x = scale;
-      scale_y = scale * (1.0 - (aspect_ratio  / 20.0));
-    }
 
   gimp_matrix3_identity (matrix);
   gimp_matrix3_scale (matrix, scale_x, scale_y);
diff --git a/app/core/gimpbrush-transform.h b/app/core/gimpbrush-transform.h
index 6e93529663..5f7cbcb74a 100644
--- a/app/core/gimpbrush-transform.h
+++ b/app/core/gimpbrush-transform.h
@@ -43,10 +43,14 @@ GimpTempBuf * gimp_brush_real_transform_pixmap (GimpBrush   *brush,
                                                 gboolean     reflect,
                                                 gdouble      hardness);
 
+void          gimp_brush_transform_get_scale   (gdouble      scale,
+                                                gdouble      aspect_ratio,
+                                                gdouble     *scale_x,
+                                                gdouble     *scale_y);
 void          gimp_brush_transform_matrix      (gdouble      width,
                                                 gdouble      height,
-                                                gdouble      scale,
-                                                gdouble      aspect_ratio,
+                                                gdouble      scale_x,
+                                                gdouble      scale_y,
                                                 gdouble      angle,
                                                 gboolean     reflect,
                                                 GimpMatrix3 *matrix);