added a few functions to test for matrix properties

Fri Jul  9 16:47:04 MEST 1999  Sven Neumann <sven@gimp.org>

        * libgimp/gimpmatrix.[ch]: added a few functions to test for
        matrix properties

        * app/transform_core.c: if we are doing a simple transformation
        (e.g. rotating by 90 degrees), turn off interpolation

        * app/rotate_tool.c: persuade the slider that a rotate angle of
        180 degrees is perfectly ok


--Sven

ChangeLog

@@ -1,3 +1,14 @@
+Fri Jul  9 16:47:04 MEST 1999  Sven Neumann <sven@gimp.org>
+
+	* libgimp/gimpmatrix.[ch]: added a few functions to test for
+	matrix properties
+
+	* app/transform_core.c: if we are doing a simple transformation
+	(e.g. rotating by 90 degrees), turn off interpolation
+
+	* app/rotate_tool.c: persuade the slider that a rotate angle of
+	180 degrees is perfectly ok
+
 1999-07-09  Michael Natterer  <mitschel@cs.tu-berlin.de>
 
 	* app/crop.c: mysteriously, using the new tool constructor fixed

app/rotate_tool.c

@@ -95,8 +95,9 @@ rotate_tool_transform (Tool     *tool,
 					tool);
 	  gtk_spin_button_set_wrap (GTK_SPIN_BUTTON (widget), TRUE);
 
+	  /*  this looks strange (-180, 181), but it works  */
 	  widget = info_dialog_add_scale (transform_info, "", &angle_val,
-					  -180, 180, 0.01, 0.1, 1, -1,
+					  -180, 181, 0.01, 0.1, 1, -1,
 					  (GtkSignalFunc) rotate_angle_changed,
 					  tool);
 	  gtk_widget_set_usize (widget, 180, 0);

app/tools/gimprotatetool.c

@@ -95,8 +95,9 @@ rotate_tool_transform (Tool     *tool,
 					tool);
 	  gtk_spin_button_set_wrap (GTK_SPIN_BUTTON (widget), TRUE);
 
+	  /*  this looks strange (-180, 181), but it works  */
 	  widget = info_dialog_add_scale (transform_info, "", &angle_val,
-					  -180, 180, 0.01, 0.1, 1, -1,
+					  -180, 181, 0.01, 0.1, 1, -1,
 					  (GtkSignalFunc) rotate_angle_changed,
 					  tool);
 	  gtk_widget_set_usize (widget, 180, 0);

app/tools/rotate_tool.c

@@ -95,8 +95,9 @@ rotate_tool_transform (Tool     *tool,
 					tool);
 	  gtk_spin_button_set_wrap (GTK_SPIN_BUTTON (widget), TRUE);
 
+	  /*  this looks strange (-180, 181), but it works  */
 	  widget = info_dialog_add_scale (transform_info, "", &angle_val,
-					  -180, 180, 0.01, 0.1, 1, -1,
+					  -180, 181, 0.01, 0.1, 1, -1,
 					  (GtkSignalFunc) rotate_angle_changed,
 					  tool);
 	  gtk_widget_set_usize (widget, 180, 0);

app/tools/transform_core.c

@@ -1026,6 +1026,10 @@ transform_core_do (GImage          *gimage,
   int newval;
 
   alpha = 0;
+  
+  /*  turn interpolation off for simple transformations (e.g. rot90)  */
+  if (gimp_matrix_is_simple (matrix))
+    interpolation = FALSE;
 
   /*  Get the background color  */
   gimage_get_background (gimage, drawable, bg_col);
@@ -1062,7 +1066,7 @@ transform_core_do (GImage          *gimage,
       gimp_matrix_invert (matrix, m);
     }
 
-  paths_transform_current_path(gimage,matrix,FALSE);
+  paths_transform_current_path (gimage, matrix, FALSE);
 
   x1 = float_tiles->x;
   y1 = float_tiles->y;
@@ -1128,6 +1132,7 @@ transform_core_do (GImage          *gimage,
       ty = yinc * (tx1 + 0.5) + m[1][1] * (y + 0.5) + m[1][2];
       tw = winc * (tx1 + 0.5) + m[2][1] * (y + 0.5) + m[2][2];
       d = dest;
+
       for (x = tx1; x < tx2; x++)
 	{
 	  /*  normalize homogeneous coords  */

app/transform_core.c

@@ -1026,6 +1026,10 @@ transform_core_do (GImage          *gimage,
   int newval;
 
   alpha = 0;
+  
+  /*  turn interpolation off for simple transformations (e.g. rot90)  */
+  if (gimp_matrix_is_simple (matrix))
+    interpolation = FALSE;
 
   /*  Get the background color  */
   gimage_get_background (gimage, drawable, bg_col);
@@ -1062,7 +1066,7 @@ transform_core_do (GImage          *gimage,
       gimp_matrix_invert (matrix, m);
     }
 
-  paths_transform_current_path(gimage,matrix,FALSE);
+  paths_transform_current_path (gimage, matrix, FALSE);
 
   x1 = float_tiles->x;
   y1 = float_tiles->y;
@@ -1128,6 +1132,7 @@ transform_core_do (GImage          *gimage,
       ty = yinc * (tx1 + 0.5) + m[1][1] * (y + 0.5) + m[1][2];
       tw = winc * (tx1 + 0.5) + m[2][1] * (y + 0.5) + m[2][2];
       d = dest;
+
       for (x = tx1; x < tx2; x++)
 	{
 	  /*  normalize homogeneous coords  */

libgimp/gimpmatrix.c

@@ -17,9 +17,12 @@
  * Boston, MA 02111-1307, USA.
  */
 
-#include "gimpmatrix.h"
+#include <glib.h>
 #include <math.h>
 #include <string.h>
+#include "gimpmatrix.h"
+
+#define EPSILON 1e-6
 
 void
 gimp_matrix_transform_point (GimpMatrix m, double x, double y,
@@ -175,5 +178,74 @@ gimp_matrix_invert (GimpMatrix m, GimpMatrix m_inv)
 void
 gimp_matrix_duplicate (GimpMatrix src, GimpMatrix target)
 {
-  memcpy(&target[0][0], &src[0][0], sizeof(GimpMatrix));
+  memcpy (&target[0][0], &src[0][0], sizeof(GimpMatrix));
 }
+
+
+/*  functions to test for matrix properties  */
+
+int
+gimp_matrix_is_diagonal (GimpMatrix m)
+{
+  int i,j;
+
+  for (i = 0; i < 3; i++)
+    {
+      for (j = 0; j < 3; j++)
+	{
+	  if (i != j && fabs (m[i][j]) > EPSILON)
+	    return FALSE;
+	}
+    }
+  return TRUE;
+}
+
+int
+gimp_matrix_is_identity (GimpMatrix m)
+{
+  int i,j;
+
+  for (i = 0; i < 3; i++)
+    {
+      for (j = 0; j < 3; j++)
+	{
+	  if (i == j)
+	    {
+	      if (fabs (m[i][j] - 1.0) > EPSILON)
+		return FALSE;
+	    }
+	  else
+	    {
+	      if (fabs (m[i][j]) > EPSILON)
+		return FALSE;
+	    }
+	}
+    }
+  return TRUE;
+}
+
+/*  Check if we'll need to interpolate when applying this matrix. 
+    This function returns TRUE if all entries of the upper left 
+    2x2 matrix are either 0 or 1 
+ */
+int
+gimp_matrix_is_simple (GimpMatrix m)
+{
+  double absm;
+  int i,j;
+
+  for (i = 0; i < 2; i++)
+    {
+      for (j = 0; j < 2; j++)
+	{
+	  absm = fabs (m[i][j]);
+	  if (absm > EPSILON && fabs (absm - 1.0) > EPSILON)
+	    return FALSE;
+	}
+    }
+  return TRUE;
+}
+
+
+
+

libgimp/gimpmatrix.h

@@ -38,9 +38,19 @@ void          gimp_matrix_yshear          (GimpMatrix, double);
 double        gimp_matrix_determinant     (GimpMatrix);
 void          gimp_matrix_invert          (GimpMatrix m, GimpMatrix m_inv);
 void          gimp_matrix_duplicate       (GimpMatrix src, GimpMatrix target);
+int           gimp_matrix_is_diagonal     (GimpMatrix m);
+int           gimp_matrix_is_identity     (GimpMatrix m);
+int           gimp_matrix_is_simple       (GimpMatrix m);
 
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
 
 #endif  /*  __GIMPMATRIX_H__  */
+
+
+
+
+
+
+