Add basic matrix transforms

Add a row-major order 3x3 float transformation matrix
and translation/reflection/rotation operations.

Makefile.am

@@ -103,6 +103,7 @@ nobase_libmypaint_public_HEADERS = \
 	mypaint-config.h				\
 	mypaint-glib-compat.h			\
 	mypaint-mapping.h				\
+	mypaint-matrix.h	\
 	$(MyPaint_introspectable_headers)
 
 LIBMYPAINT_SOURCES = \
@@ -116,6 +117,7 @@ LIBMYPAINT_SOURCES = \
 	mypaint-brush.c					\
 	mypaint-brush-settings.c		\
 	mypaint-fixed-tiled-surface.c	\
+	mypaint-matrix.c	\
 	mypaint-rectangle.c				\
 	mypaint-surface.c				\
 	mypaint-tiled-surface.c			\

mypaint-matrix.c

@@ -0,0 +1,92 @@
+/* libmypaint - The MyPaint Brush Library
+ * Copyright (C) 2019 The MyPaint Team
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "mypaint-matrix.h"
+#include <math.h>
+
+MyPaintTransform
+mypaint_matrix_multiply(const MyPaintTransform m1, const MyPaintTransform m2)
+{
+    MyPaintTransform result;
+    for (int row = 0; row < 3; ++row) {
+      for (int col = 0; col < 3; ++col) {
+	  result.rows[row][col] =
+	    m1.rows[0][col] * m2.rows[row][0] +
+	    m1.rows[1][col] * m2.rows[row][1] +
+	    m1.rows[2][col] * m2.rows[row][2];
+        }
+    }
+    return result;
+}
+
+MyPaintTransform
+mypaint_transform_unit()
+{
+    MyPaintTransform m = {{{1, 0, 0}, {0, 1, 0}, {0, 0, 1}}};
+    return m;
+}
+
+MyPaintTransform
+mypaint_transform_rotate_cw(const MyPaintTransform transform, const float angle_radians)
+{
+    const float a = angle_radians;
+    MyPaintTransform factor = {{{cos(a), sin(a), 0}, {-sin(a), cos(a), 0}, {0, 0, 1}}};
+    return mypaint_matrix_multiply(transform, factor);
+}
+
+MyPaintTransform
+mypaint_transform_rotate_ccw(const MyPaintTransform transform, const float angle_radians)
+{
+    const float a = angle_radians;
+    MyPaintTransform factor = {{
+        {cos(a), -sin(a), 0},
+        {sin(a), cos(a), 0},
+        {0, 0, 1},
+    }};
+    return mypaint_matrix_multiply(transform, factor);
+}
+
+MyPaintTransform
+mypaint_transform_reflect(const MyPaintTransform transform, const float angle_radians)
+{
+    float x = cos(angle_radians);
+    float y = sin(angle_radians);
+    MyPaintTransform factor = {{
+        {x * x - y * y, 2.0 * x * y, 0},
+        {2.0 * x * y, y * y - x * x, 0},
+        {0, 0, 1},
+    }};
+    return mypaint_matrix_multiply(transform, factor);
+}
+
+
+MyPaintTransform
+mypaint_transform_translate(const MyPaintTransform transform, const float x, const float y)
+{
+    MyPaintTransform factor = {{
+	{1, 0, x},
+	{0, 1, y},
+	{0, 0, 1},
+      }};
+    return mypaint_matrix_multiply(transform, factor);
+}
+
+void
+mypaint_transform_point(const MyPaintTransform* const t, float x, float y, float* xout, float* yout)
+{
+    *xout = t->rows[0][0] * x + t->rows[0][1] * y + t->rows[0][2];
+    *yout = t->rows[1][0] * x + t->rows[1][1] * y + t->rows[1][2];
+}

mypaint-matrix.h

@@ -0,0 +1,32 @@
+#ifndef MYPAINTMATRIX_H
+#define MYPAINTMATRIX_H
+
+/* libmypaint - The MyPaint Brush Library
+ * Copyright (C) 2019 The MyPaint Team
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+typedef struct {
+  float rows[3][3];
+} MyPaintTransform;
+
+MyPaintTransform mypaint_transform_unit();
+MyPaintTransform mypaint_transform_rotate_cw(const MyPaintTransform transform, const float angle_radians);
+MyPaintTransform mypaint_transform_rotate_ccw(const MyPaintTransform transform, const float angle_radians);
+MyPaintTransform mypaint_transform_reflect(const MyPaintTransform transform, const float angle_radians);
+MyPaintTransform mypaint_transform_translate(const MyPaintTransform transform, const float x, const float y);
+
+void mypaint_transform_point(const MyPaintTransform* const t, float x, float y, float* x_out, float* y_out);
+
+#endif