[gegl] buffer: add gegl_buffer_matrix2_is_identity()

[Ell <ell src gnome org>]

commit 6a940eddd37175664b9679295a652449ff5068af
Author: Ell <ell_se yahoo com>
Date:   Thu Nov 15 14:29:29 2018 -0500

    buffer: add gegl_buffer_matrix2_is_identity()
    
    ... which checks if a GeglBufferMatrix2 is the identity.

 gegl/buffer/gegl-buffer-matrix2.c |  8 +++++++-
 gegl/buffer/gegl-buffer-matrix2.h | 14 ++++++++++++--
 2 files changed, 19 insertions(+), 3 deletions(-)
---
diff --git a/gegl/buffer/gegl-buffer-matrix2.c b/gegl/buffer/gegl-buffer-matrix2.c
index 0842e9781..20b0e168c 100644
--- a/gegl/buffer/gegl-buffer-matrix2.c
+++ b/gegl/buffer/gegl-buffer-matrix2.c
@@ -20,6 +20,13 @@
 #include "gegl-buffer-matrix2.h"
 
 
+gboolean
+gegl_buffer_matrix2_is_identity (GeglBufferMatrix2 *matrix)
+{
+  return matrix->coeff[0][0] == 1.0 && matrix->coeff[0][1] == 0.0 &&
+         matrix->coeff[1][0] == 0.0 && matrix->coeff[1][1] == 1.0;
+}
+
 gboolean
 gegl_buffer_matrix2_is_scale (GeglBufferMatrix2 *matrix)
 {
@@ -32,4 +39,3 @@ gegl_buffer_matrix2_determinant (GeglBufferMatrix2 *matrix)
   return matrix->coeff[0][0] * matrix->coeff[1][1] -
          matrix->coeff[1][0] * matrix->coeff[0][1];
 }
-
diff --git a/gegl/buffer/gegl-buffer-matrix2.h b/gegl/buffer/gegl-buffer-matrix2.h
index da99a6a2a..1454d3b33 100644
--- a/gegl/buffer/gegl-buffer-matrix2.h
+++ b/gegl/buffer/gegl-buffer-matrix2.h
@@ -32,6 +32,16 @@ typedef struct {
     gdouble coeff[2][2];
 } GeglBufferMatrix2;
 
+/*
+ * gegl_buffer_matrix2_is_identity:
+ * @matrix: a #GeglBufferMatrix2
+ *
+ * Check if a matrix is the identity matrix.
+ *
+ * Returns TRUE if the matrix is the identity matrix.
+ */
+gboolean   gegl_buffer_matrix2_is_identity (GeglBufferMatrix2 *matrix);
+
 /*
  * gegl_buffer_matrix2_is_scale:
  * @matrix: a #GeglBufferMatrix2
@@ -40,7 +50,7 @@ typedef struct {
  *
  * Returns TRUE if the matrix only does scaling.
  */
-gboolean   gegl_buffer_matrix2_is_scale        (GeglBufferMatrix2 *matrix);
+gboolean   gegl_buffer_matrix2_is_scale    (GeglBufferMatrix2 *matrix);
 
 /*
  * gegl_buffer_matrix2_determinant:
@@ -48,7 +58,7 @@ gboolean   gegl_buffer_matrix2_is_scale        (GeglBufferMatrix2 *matrix);
  *
  * Returns the determinant of @matrix.
  */
-gdouble    gegl_buffer_matrix2_determinant     (GeglBufferMatrix2 *matrix);
+gdouble    gegl_buffer_matrix2_determinant (GeglBufferMatrix2 *matrix);
 
 
 G_END_DECLS