Add support for character mirroring and add functions for creating transformations

Signed-off-by: Mattias Andrée <maandree@kth.se>

15 files changed, 192 insertions, 42 deletions

diff --git a/Makefile b/Makefile
index 4c70752..85769d0 100644
--- a/Makefile
+++ b/Makefile
@@ -4,6 +4,16 @@ CONFIGFILE = config.mk
 include $(CONFIGFILE)
 
 OBJ =\
+	libskrift_add_180_degree_rotation.o\
+	libskrift_add_270_degree_rotation.o\
+	libskrift_add_90_degree_rotation.o\
+	libskrift_add_rotation.o\
+	libskrift_add_rotation_degrees.o\
+	libskrift_add_scaling.o\
+	libskrift_add_shear.o\
+	libskrift_add_transformation.o\
+	libskrift_add_translation.o\
+	libskrift_add_transposition.o\
 	libskrift_apply_glyph.o\
 	libskrift_calculate_dpi.o\
 	libskrift_close_font.o\
diff --git a/README b/README
index bfa17bf..f7327d9 100644
--- a/README
+++ b/README
@@ -36,6 +36,8 @@ Currently implemented:
 
 	sRGB gamma function.
 
+	Affine transformations on glyphs.
+
 
 Pending support in libschift:
 
@@ -44,7 +46,7 @@ Pending support in libschift:
 	Hinting.
 	(Better subpixel rendering requires subpixel aware hinting.)
 
-	Affine transformations on glyphs, texts, part of outline.
+	Affine transformations on parts of outline.
 
 	Kerning using font information.
 
@@ -53,6 +55,8 @@ Pending support in libschift:
 
 Not implemented yet
 
+	Affine transformations on texts.
+
 	Glyph caching.
 
 	Normalise text when glyphs are missing.
diff --git a/demo.c b/demo.c
index a4d998c..c6a27d2 100644
--- a/demo.c
+++ b/demo.c
@@ -11,24 +11,19 @@ main(void)
 	LIBSKRIFT_CONTEXT *ctx;
 	struct libskrift_image image = {LIBSKRIFT_R8G8B8A8, LIBSKRIFT_HOST_SUBPIXEL, 0, 800, 600, NULL, NULL, NULL};
 	struct libskrift_rendering rendering = LIBSKRIFT_DEFAULT_RENDERING;
-	struct libskrift_colour colour = LIBSKRIFT_PREMULTIPLY(0.8f, 0.25f, .80f, .50f, .20f);
+	struct libskrift_colour colour = LIBSKRIFT_PREMULTIPLY(.80f, .50f, .80f, .50f, .20f);
 	double height;
 	size_t size, i;
 
 	rendering.smoothing      = LIBSKRIFT_SUBPIXEL;
 	rendering.subpixel_order = LIBSKRIFT_NONE;
-	rendering.flags          = 0;
+	rendering.flags          = LIBSKRIFT_MIRROR_CHARS;
 
 	if (libskrift_open_font_file(&font, DEMO_FONT)) {
 		perror("libskrift_open_font_file");
 		return -1;
 	}
-	rendering.char_transformation[0] = 1;
-	rendering.char_transformation[1] = 0.25;
-	rendering.char_transformation[2] = 0;
-	rendering.char_transformation[3] = 0;
-	rendering.char_transformation[4] = 1;
-	rendering.char_transformation[5] = 0;
+	libskrift_add_rotation_degrees(rendering.char_transformation, 10);
 	height = libskrift_points_to_pixels(72, &rendering);
 	if (libskrift_create_context(&ctx, &font, 1, height, &rendering, NULL)) {
 		perror("libskrift_create_context");
diff --git a/libskrift.h b/libskrift.h
index 843de6e..57eb4d1 100644
--- a/libskrift.h
+++ b/libskrift.h
@@ -2,6 +2,7 @@
 #ifndef LIBSKRIFT_H
 #define LIBSKRIFT_H 1
 
+#include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -86,25 +87,25 @@ enum libskrift_hinting {
 	LIBSKRIFT_FULL     = 100
 };
 
-#define LIBSKRIFT_REMOVE_GAMMA         0x00000001L
-#define LIBSKRIFT_Y_INCREASES_UPWARDS  0x00000002L /* SFT_DOWNWARD_Y otherwise */
-#define LIBSKRIFT_FLIP_TEXT            0x00000004L
-#define LIBSKRIFT_FLIP_CHARS           0x00000008L
-#define LIBSKRIFT_MIRROR_TEXT          0x00000010L
-#define LIBSKRIFT_MIRROR_CHARS         0x00000020L
-#define LIBSKRIFT_TRANSPOSE_TEXT       0x00000040L
-#define LIBSKRIFT_TRANSPOSE_CHARS      0x00000080L
-#define LIBSKRIFT_NO_LIGATURES         0x00000100L
-#define LIBSKRIFT_ADVANCE_CHAR_TO_GRID 0x00000200L
-#define LIBSKRIFT_REGRESS_CHAR_TO_GRID 0x00000400L /* Combine with LIBSKRIFT_ADVANCE_CHAR_TO_GRID for closest alternative */
-#define LIBSKRIFT_ADVANCE_WORD_TO_GRID 0x00000800L
-#define LIBSKRIFT_REGRESS_WORD_TO_GRID 0x00001000L /* Combine with LIBSKRIFT_ADVANCE_WORD_TO_GRID for closest alternative */
-#define LIBSKRIFT_USE_SUBPIXEL_GRID    0x00002000L
-#define LIBSKRIFT_VERTICAL_TEXT        0x00004000L
-#define LIBSKRIFT_AUTOHINTING          0x00008000L /* Use autohinter even if hint information exists */
-#define LIBSKRIFT_NO_AUTOHINTING       0x00010000L /* Use autohinter if no hint information exist */
-#define LIBSKRIFT_AUTOKERNING          0x00020000L /* Use autokerner even if kerning information exists */
-#define LIBSKRIFT_NO_AUTOKERNING       0x00040000L /* Use autokerner if no kerning information exist */
+#define LIBSKRIFT_REMOVE_GAMMA         UINT32_C(0x00000001)
+#define LIBSKRIFT_Y_INCREASES_UPWARDS  UINT32_C(0x00000002) /* SFT_DOWNWARD_Y otherwise */
+#define LIBSKRIFT_FLIP_TEXT            UINT32_C(0x00000004)
+#define LIBSKRIFT_FLIP_CHARS           UINT32_C(0x00000008)
+#define LIBSKRIFT_MIRROR_TEXT          UINT32_C(0x00000010)
+#define LIBSKRIFT_MIRROR_CHARS         UINT32_C(0x00000020)
+#define LIBSKRIFT_TRANSPOSE_TEXT       UINT32_C(0x00000040)
+#define LIBSKRIFT_TRANSPOSE_CHARS      UINT32_C(0x00000080)
+#define LIBSKRIFT_NO_LIGATURES         UINT32_C(0x00000100)
+#define LIBSKRIFT_ADVANCE_CHAR_TO_GRID UINT32_C(0x00000200)
+#define LIBSKRIFT_REGRESS_CHAR_TO_GRID UINT32_C(0x00000400) /* Combine with LIBSKRIFT_ADVANCE_CHAR_TO_GRID for closest alternative */
+#define LIBSKRIFT_ADVANCE_WORD_TO_GRID UINT32_C(0x00000800)
+#define LIBSKRIFT_REGRESS_WORD_TO_GRID UINT32_C(0x00001000) /* Combine with LIBSKRIFT_ADVANCE_WORD_TO_GRID for closest alternative */
+#define LIBSKRIFT_USE_SUBPIXEL_GRID    UINT32_C(0x00002000)
+#define LIBSKRIFT_VERTICAL_TEXT        UINT32_C(0x00004000)
+#define LIBSKRIFT_AUTOHINTING          UINT32_C(0x00008000) /* Use autohinter even if hint information exists */
+#define LIBSKRIFT_NO_AUTOHINTING       UINT32_C(0x00010000) /* Use autohinter if no hint information exist */
+#define LIBSKRIFT_AUTOKERNING          UINT32_C(0x00020000) /* Use autokerner even if kerning information exists */
+#define LIBSKRIFT_NO_AUTOKERNING       UINT32_C(0x00040000) /* Use autokerner if no kerning information exist */
 
 struct libskrift_rendering {
 	int struct_version;
@@ -272,4 +273,85 @@ void libskrift_srgb_preprocess(struct libskrift_image *, size_t, size_t, size_t,
 _LIBSKRIFT_GCC_ONLY(__attribute__((__nonnull__)))
 void libskrift_srgb_postprocess(struct libskrift_image *, size_t, size_t, size_t, size_t);
 
+
+inline void
+libskrift_add_transformation(double m[restrict 6], const double tm[restrict 6])
+{
+	double a = m[0], b = m[1], c = m[2];
+	double d = m[3], e = m[4], f = m[5];
+	m[0] = tm[0] * a + tm[1] * d;
+	m[1] = tm[0] * b + tm[1] * e;
+	m[2] = tm[0] * c + tm[1] * f + tm[2];
+	m[3] = tm[3] * a + tm[4] * d;
+	m[4] = tm[3] * b + tm[4] * e;
+	m[5] = tm[3] * c + tm[4] * f + tm[5];
+}
+
+inline void
+libskrift_add_rotation(double m[6], double radians)
+{
+	double c = cos(-radians), s = sin(-radians);
+	libskrift_add_transformation(m, (double []){c, -s, 0, s, c, 0});
+}
+
+inline void
+libskrift_add_rotation_degrees(double m[6], double degrees)
+{
+	libskrift_add_rotation(m, degrees * (double)0.017453292519943295f);
+}
+
+inline void
+libskrift_add_90_degree_rotation(double m[6])
+{
+	double a = m[0], b = m[1], c = m[2];
+	m[0] = m[3], m[1] = m[4], m[2] = m[5];
+	m[3] = -a,   m[4] = -b,   m[5] = -c;
+}
+
+inline void
+libskrift_add_180_degree_rotation(double m[6])
+{
+	m[0] = -m[0], m[1] = -m[1], m[2] = -m[2];
+	m[3] = -m[3], m[4] = -m[4], m[5] = -m[5];
+}
+
+inline void
+libskrift_add_270_degree_rotation(double m[6])
+{
+	double a = m[0], b = m[1], c = m[2];
+	m[0] = -m[3], m[1] = -m[4], m[2] = -m[5];
+	m[3] = a,     m[4] = b,     m[5] = c;
+}
+
+inline void
+libskrift_add_scaling(double m[6], double x, double y)
+{
+	m[0] *= x, m[1] *= x, m[2] *= x;
+	m[3] *= y, m[4] *= y, m[5] *= y;
+}
+
+inline void
+libskrift_add_transposition(double m[6])
+{
+	double a = m[0], b = m[1], c = m[2];
+	m[0] = m[3], m[1] = m[4], m[2] = m[5];
+	m[3] = a,    m[4] = b,    m[5] = c;
+}
+
+inline void
+libskrift_add_shear(double m[6], double x, double y)
+{
+	double a = m[0], b = m[1], c = m[2];
+	double d = m[3], e = m[4], f = m[6];
+	m[0] += x * d, m[1] += x * e, m[2] += x * f;
+	m[3] += y * a, m[4] += y * b, m[5] += y * c;
+}
+
+inline void
+libskrift_add_translation(double m[6], double x, double y)
+{
+	m[2] += x;
+	m[5] += y;
+}
+
 #endif
diff --git a/libskrift_add_180_degree_rotation.c b/libskrift_add_180_degree_rotation.c
new file mode 100644
index 0000000..776e7b4
--- /dev/null
+++ b/libskrift_add_180_degree_rotation.c
@@ -0,0 +1,4 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+extern inline void libskrift_add_180_degree_rotation(double m[6]);
diff --git a/libskrift_add_270_degree_rotation.c b/libskrift_add_270_degree_rotation.c
new file mode 100644
index 0000000..74a86ea
--- /dev/null
+++ b/libskrift_add_270_degree_rotation.c
@@ -0,0 +1,4 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+extern inline void libskrift_add_270_degree_rotation(double m[6]);
diff --git a/libskrift_add_90_degree_rotation.c b/libskrift_add_90_degree_rotation.c
new file mode 100644
index 0000000..5c920e0
--- /dev/null
+++ b/libskrift_add_90_degree_rotation.c
@@ -0,0 +1,4 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+extern inline void libskrift_add_90_degree_rotation(double m[6]);
diff --git a/libskrift_add_rotation.c b/libskrift_add_rotation.c
new file mode 100644
index 0000000..8b03e81
--- /dev/null
+++ b/libskrift_add_rotation.c
@@ -0,0 +1,4 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+extern inline void libskrift_add_rotation(double m[6], double radians);
diff --git a/libskrift_add_rotation_degrees.c b/libskrift_add_rotation_degrees.c
new file mode 100644
index 0000000..239003b
--- /dev/null
+++ b/libskrift_add_rotation_degrees.c
@@ -0,0 +1,4 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+extern inline void libskrift_add_rotation_degrees(double m[6], double degrees);
diff --git a/libskrift_add_scaling.c b/libskrift_add_scaling.c
new file mode 100644
index 0000000..f9d745a
--- /dev/null
+++ b/libskrift_add_scaling.c
@@ -0,0 +1,4 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+extern inline void libskrift_add_scaling(double m[6], double x, double y);
diff --git a/libskrift_add_shear.c b/libskrift_add_shear.c
new file mode 100644
index 0000000..f48c507
--- /dev/null
+++ b/libskrift_add_shear.c
@@ -0,0 +1,4 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+extern inline void libskrift_add_shear(double m[6], double x, double y);
diff --git a/libskrift_add_transformation.c b/libskrift_add_transformation.c
new file mode 100644
index 0000000..fa14990
--- /dev/null
+++ b/libskrift_add_transformation.c
@@ -0,0 +1,4 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+extern inline void libskrift_add_transformation(double m[restrict 6], const double tm[restrict 6]);
diff --git a/libskrift_add_translation.c b/libskrift_add_translation.c
new file mode 100644
index 0000000..f5e2c14
--- /dev/null
+++ b/libskrift_add_translation.c
@@ -0,0 +1,4 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+extern inline void libskrift_add_translation(double m[6], double x, double y);
diff --git a/libskrift_add_transposition.c b/libskrift_add_transposition.c
new file mode 100644
index 0000000..2b2e91d
--- /dev/null
+++ b/libskrift_add_transposition.c
@@ -0,0 +1,4 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+extern inline void libskrift_add_transposition(double m[6]);
diff --git a/libskrift_create_context.c b/libskrift_create_context.c
index cf67826..1500b20 100644
--- a/libskrift_create_context.c
+++ b/libskrift_create_context.c
@@ -6,30 +6,47 @@
                       LIBSKRIFT_NO_AUTOKERNING)
 
 #define IMPLEMENTED_FLAGS (LIBSKRIFT_REMOVE_GAMMA |\
+                           LIBSKRIFT_MIRROR_CHARS |\
                            FORCED_FLAGS) /* libschrift does not add gamma, so not handling is required */
 
+#define TRANSFORMING_FLAGS (LIBSKRIFT_MIRROR_TEXT    |\
+                            LIBSKRIFT_MIRROR_CHARS   |\
+                            LIBSKRIFT_TRANSPOSE_TEXT |\
+                            LIBSKRIFT_TRANSPOSE_CHARS)
+
 #define COPY_ARRAY(DEST_STRUCT, SRC_STRUCT, FIELD)\
 	memcpy((DEST_STRUCT).FIELD, (SRC_STRUCT).FIELD, sizeof((SRC_STRUCT).FIELD))
 
 static const struct libskrift_rendering default_rendering = LIBSKRIFT_DEFAULT_RENDERING;
 
+static void
+multiply_matrices(const double a[restrict 6], const double b[restrict 6], double r[restrict 6])
+{
+	r[0] = a[0] * b[0] + a[1] * b[3];
+	r[1] = a[0] * b[1] + a[1] * b[4];
+	r[2] = a[0] * b[2] + a[1] * b[5] + a[2];
+	r[3] = a[3] * b[0] + a[4] * b[3];
+	r[4] = a[3] * b[1] + a[4] * b[4];
+	r[5] = a[3] * b[2] + a[4] * b[5] + a[5];
+}
+
 static int
 transformation_hook(void *hook_data, double advance, double transform[6])
 {
 	LIBSKRIFT_CONTEXT *ctx = hook_data;
-	double r1c1b = ctx->rendering.char_transformation[0], r1c1a = transform[0];
-	double r1c2b = ctx->rendering.char_transformation[1], r1c2a = transform[2];
-	double r1c3b = ctx->rendering.char_transformation[2], r1c3a = transform[4];
-	double r2c1b = ctx->rendering.char_transformation[3], r2c1a = transform[1];
-	double r2c2b = ctx->rendering.char_transformation[4], r2c2a = transform[3];
-	double r2c3b = ctx->rendering.char_transformation[5], r2c3a = transform[5];
-	transform[0] = r1c1a * r1c1b + r1c2a * r2c1b;
-	transform[2] = r1c1a * r1c2b + r1c2a * r2c2b;
-	transform[4] = r1c1a * r1c3b + r1c2a * r2c3b + r1c3a;
-	transform[1] = r2c1a * r1c1b + r2c2a * r2c1b;
-	transform[3] = r2c1a * r1c2b + r2c2a * r2c2b;
-	transform[5] = r2c1a * r1c3b + r2c2a * r2c3b + r2c3a;
-	(void) advance;
+	double schrift[6] = {transform[0], transform[2], transform[4],
+	                     transform[1], transform[3], transform[5]};
+	double m1[6] = {1, 0, 0, 0, 1, 0}, m2[6] = {1, 0, 0, 0, 1, 0};
+	if (((ctx->rendering.flags / LIBSKRIFT_MIRROR_CHARS) ^ (ctx->rendering.flags / LIBSKRIFT_MIRROR_TEXT)) & 1)
+		multiply_matrices((double []){-1, 0, advance / schrift[0], 0, 1, 0}, m2, m1);
+	multiply_matrices(ctx->rendering.char_transformation, m1, m2);
+	multiply_matrices(schrift, m2, m1);
+	transform[0] = m1[0];
+	transform[2] = m1[1];
+	transform[4] = m1[2];
+	transform[1] = m1[3];
+	transform[3] = m1[4];
+	transform[5] = m1[5];
 	return 0;
 }
 
@@ -82,6 +99,7 @@ libskrift_create_context(LIBSKRIFT_CONTEXT **ctxp, LIBSKRIFT_FONT **fonts, size_
 	(*ctxp)->rendering.hinting             = LIBSKRIFT_NONE;
 	(*ctxp)->rendering.flags              &= IMPLEMENTED_FLAGS;
 	(*ctxp)->rendering.flags              |= FORCED_FLAGS;
+	(*ctxp)->rendering.flags              |= LIBSKRIFT_REMOVE_GAMMA; /* libschrift does not add gamma */
 	(*ctxp)->rendering.grid_fineness       = 1;
 	(*ctxp)->rendering.kerning             = 0;
 	(*ctxp)->rendering.interletter_spacing = 0;
@@ -92,7 +110,8 @@ libskrift_create_context(LIBSKRIFT_CONTEXT **ctxp, LIBSKRIFT_FONT **fonts, size_
 	(*ctxp)->schrift_ctx.xScale = (*ctxp)->schrift_ctx.yScale;
 	(*ctxp)->schrift_ctx.xScale *= (*ctxp)->rendering.horizontal_dpi / (*ctxp)->rendering.vertical_dpi;
 	(*ctxp)->schrift_ctx.hook_data = (*ctxp);
-	if (fpclassify((*ctxp)->rendering.char_transformation[0] - 1) != FP_ZERO ||
+	if (((*ctxp)->rendering.flags & TRANSFORMING_FLAGS) ||
+	    fpclassify((*ctxp)->rendering.char_transformation[0] - 1) != FP_ZERO ||
 	    fpclassify((*ctxp)->rendering.char_transformation[1]) != FP_ZERO ||
 	    fpclassify((*ctxp)->rendering.char_transformation[2]) != FP_ZERO ||
 	    fpclassify((*ctxp)->rendering.char_transformation[3]) != FP_ZERO ||