Add libfonts_{get,unget}_subpixel_order_class

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

4 files changed, 271 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 74bb9e1..9ff12b7 100644
--- a/Makefile
+++ b/Makefile
@@ -21,7 +21,9 @@ OBJ =\
 	libfonts_decode_font_description.o\
 	libfonts_encode_font_description.o\
 	libfonts_get_default_font_name.o\
-	libfonts_get_output_dpi.o
+	libfonts_get_output_dpi.o\
+	libfonts_get_subpixel_order_class.o\
+	libfonts_unget_subpixel_order_class.o
 
 HDR =\
 	common.h\
diff --git a/libfonts.h b/libfonts.h
index e6460f9..bd03ccd 100644
--- a/libfonts.h
+++ b/libfonts.h
@@ -68,6 +68,142 @@ enum libfonts_antialiasing {
 
 
 /**
+ * Output subpixel colour
+ */
+enum libfonts_subpixel_colour {
+	/**
+	 * Red primary
+	 */
+	LIBFONTS_SUBPIXEL_COLOUR_RED = 0,
+
+	/**
+	 * Green primary
+	 */
+	LIBFONTS_SUBPIXEL_COLOUR_GREEN = 1,
+
+	/**
+	 * Blue primary
+	 */
+	LIBFONTS_SUBPIXEL_COLOUR_BLUE = 2
+};
+
+/**
+ * Output subpixel order class
+ */
+enum libfonts_subpixel_order_class {
+	/**
+	 * `LIBFONTS_SUBPIXEL_ORDER_UNKNOWN`,
+	 * `LIBFONTS_SUBPIXEL_ORDER_NONRGB`,
+	 * `LIBFONTS_SUBPIXEL_ORDER_NONLINEAR`, or
+	 * `LIBFONTS_SUBPIXEL_ORDER_OTHER`
+	 */
+	LIBFONTS_SUBPIXEL_ORDER_CLASS_OTHER,
+
+	/**
+	 * ┌───┬───┬───┐
+	 * │   │   │   │
+	 * │   │   │   │
+	 * │ 1 │ 2 │ 3 │
+	 * │   │   │   │
+	 * │   │   │   │
+	 * └───┴───┴───┘
+	 */
+	LIBFONTS_SUBPIXEL_ORDER_CLASS_123,
+
+	/**
+	 * ┌───────────┐
+	 * │     1     │
+	 * ├───────────┤
+	 * │     2     │
+	 * ├───────────┤
+	 * │     3     │
+	 * └───────────┘
+	 */
+	LIBFONTS_SUBPIXEL_ORDER_CLASS_1_2_3,
+
+	/**
+	 * ┌───────┐
+	 * │   1   │
+	 * ├───┬───┤
+	 * │ 2 │ 3 │
+	 * └───┴───┘
+	 */
+	LIBFONTS_SUBPIXEL_ORDER_CLASS_11_23,
+
+	/**
+	 * ┌───┬───┐
+	 * │ 2 │   │
+	 * ├───┤ 1 │
+	 * │ 3 │   │
+	 * └───┴───┘
+	 */
+	LIBFONTS_SUBPIXEL_ORDER_CLASS_21_31,
+
+	/**
+	 * ┌───┬───┐
+	 * │ 3 │ 2 │
+	 * ├───┴───┤
+	 * │   1   │
+	 * └───────┘
+	 */
+	LIBFONTS_SUBPIXEL_ORDER_CLASS_32_11,
+
+	/**
+	 * ┌───┬───┐
+	 * │   │ 3 │
+	 * │ 1 ├───┤
+	 * │   │ 2 │
+	 * └───┴───┘
+	 */
+	LIBFONTS_SUBPIXEL_ORDER_CLASS_13_12,
+
+	/**
+	 * ┌───────────┐
+	 * │     1     │
+	 * ├─────┬─────┤
+	 * │     │     │
+	 * │  2  │  3  │
+	 * │     │     │
+	 * └─────┴─────┘
+	 */
+	LIBFONTS_SUBPIXEL_ORDER_CLASS_BALANCED_11_23,
+
+	/**
+	 * ┌───────┬───┐
+	 * │   2   │   │
+	 * │       │   │
+	 * ├───────┤ 1 │
+	 * │   3   │   │
+	 * │       │   │
+	 * └───────┴───┘
+	 */
+	LIBFONTS_SUBPIXEL_ORDER_CLASS_BALANCED_21_31,
+
+	/**
+	 * ┌─────┬─────┐
+	 * │     │     │
+	 * │  3  │  2  │
+	 * │     │     │
+	 * ├─────┴─────┤
+	 * │     1     │
+	 * └───────────┘
+	 */
+	LIBFONTS_SUBPIXEL_ORDER_CLASS_BALANCED_32_11,
+
+	/**
+	 * ┌───┬───────┐
+	 * │   │   3   │
+	 * │   │       │
+	 * │ 1 ├───────┤
+	 * │   │   2   │
+	 * │   │       │
+	 * └───┴───────┘
+	 */
+	LIBFONTS_SUBPIXEL_ORDER_CLASS_BALANCED_13_12
+};
+
+
+/**
  * Output subpixel order
  */
 enum libfonts_subpixel_order {
@@ -1342,5 +1478,45 @@ int libfonts_get_output_dpi(struct libfonts_output *, const char *);
  */
 enum libfonts_subpixel_order libfonts_calculate_subpixel_order(enum libfonts_subpixel_order, const struct libfonts_transformation *);
 
+/**
+ * Get the general subpixel layout, as well
+ * as which primary is contained in which
+ * cell in the layout, from a specific
+ * subpixel order
+ *
+ * @param   order   The subpixel order
+ * @param   cell1p  Output parameter for the primary contained in cell 1
+ * @param   cell2p  Output parameter for the primary contained in cell 2
+ * @param   cell3p  Output parameter for the primary contained in cell 3
+ * @return          The subpixel layout
+ */
+enum libfonts_subpixel_order_class libfonts_get_subpixel_order_class(enum libfonts_subpixel_order,
+                                                                     enum libfonts_subpixel_colour *,
+                                                                     enum libfonts_subpixel_colour *,
+                                                                     enum libfonts_subpixel_colour *);
+
+/**
+ * Get the general subpixel layout, as well
+ * as which primary is contained in which
+ * cell in the layout, from a specific
+ * subpixel order
+ *
+ * @param    orderp  Output parameter for the subpixel order
+ * @param    layout  The subpixel layout
+ * @param    cell1   The primary contained in cell 1
+ * @param    cell2   The primary contained in cell 2
+ * @param    cell3   The primary contained in cell 3
+ * @return           Normally 1, but 0 if `layout` is `LIBFONTS_SUBPIXEL_ORDER_CLASS_OTHER`;
+ *                   -1 on failure
+ * 
+ * @throws  EINVAL  Unrecognised value in `layout`, `cell1`, `cell2`, or `cell3`
+ * @throws  EINVAL  The values of `cell1`, `cell2`, and `cell3` are not unique
+ */
+int libfonts_unget_subpixel_order_class(enum libfonts_subpixel_order *,
+                                        enum libfonts_subpixel_order_class,
+                                        enum libfonts_subpixel_colour,
+                                        enum libfonts_subpixel_colour,
+                                        enum libfonts_subpixel_colour);
+
 
 #endif
diff --git a/libfonts_get_subpixel_order_class.c b/libfonts_get_subpixel_order_class.c
new file mode 100644
index 0000000..577b0f0
--- /dev/null
+++ b/libfonts_get_subpixel_order_class.c
@@ -0,0 +1,41 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+enum libfonts_subpixel_order_class
+libfonts_get_subpixel_order_class(enum libfonts_subpixel_order order,
+                                  enum libfonts_subpixel_colour *cell1p,
+                                  enum libfonts_subpixel_colour *cell2p,
+                                  enum libfonts_subpixel_colour *cell3p)
+{
+	enum libfonts_subpixel_colour c1, c2, c3;
+	enum libfonts_subpixel_order_class layout;
+	int i; /* RGB, RBG, GRB, GBR, BRG, BGR */
+
+	if (order >= LIBFONTS_SUBPIXEL_ORDER_RGB && order <= LIBFONTS_SUBPIXEL_ORDER_G_R_B) {
+		layout = ((order - LIBFONTS_SUBPIXEL_ORDER_RGB) & 1) + LIBFONTS_SUBPIXEL_ORDER_CLASS_123;
+		i = (order - LIBFONTS_SUBPIXEL_ORDER_RGB) / 2;
+		i = ((int []){0, 5, 3, 1, 4, 2})[i];
+
+	} else if (order >= LIBFONTS_SUBPIXEL_ORDER_RR_GB && order <= LIBFONTS_SUBPIXEL_ORDER_BALANCED_BR_BG) {
+		layout = ((order - LIBFONTS_SUBPIXEL_ORDER_RR_GB) & 3) + LIBFONTS_SUBPIXEL_ORDER_CLASS_11_23;
+		if (order >= LIBFONTS_SUBPIXEL_ORDER_BALANCED_RR_GB)
+			layout += 4;
+		i = (order - LIBFONTS_SUBPIXEL_ORDER_RR_GB) / 4 % 6;
+
+	} else {
+		layout = LIBFONTS_SUBPIXEL_ORDER_CLASS_OTHER;
+		i = 0;
+	}
+
+	c1 = i / 2;
+	c2 = (i + 1 + i / 3) % 3;
+	c3 = 3 - c1 - c2;
+	if (cell1p)
+		*cell1p = c1;
+	if (cell2p)
+		*cell2p = c2;
+	if (cell3p)
+		*cell3p = c3;
+	return layout;
+}
diff --git a/libfonts_unget_subpixel_order_class.c b/libfonts_unget_subpixel_order_class.c
new file mode 100644
index 0000000..5fa9274
--- /dev/null
+++ b/libfonts_unget_subpixel_order_class.c
@@ -0,0 +1,51 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+int
+libfonts_unget_subpixel_order_class(enum libfonts_subpixel_order *orderp,
+                                    enum libfonts_subpixel_order_class layout,
+                                    enum libfonts_subpixel_colour cell1,
+                                    enum libfonts_subpixel_colour cell2,
+                                    enum libfonts_subpixel_colour cell3)
+{
+	int i;
+
+	if (cell1 < 0 || cell1 > 2 ||
+	    cell2 < 0 || cell2 > 2 ||
+	    cell3 < 0 || cell3 > 2 ||
+	    cell1 == cell2 ||
+	    cell2 == cell3 ||
+	    cell3 == cell1) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	if (layout == LIBFONTS_SUBPIXEL_ORDER_CLASS_OTHER) {
+		if (orderp)
+			*orderp = LIBFONTS_SUBPIXEL_ORDER_UNKNOWN;
+		return 0;
+
+	} else if (layout == LIBFONTS_SUBPIXEL_ORDER_CLASS_123 || layout == LIBFONTS_SUBPIXEL_ORDER_CLASS_1_2_3) {
+		if (orderp) {
+			/* RGB, BGR, GBR, RBG, BRG, GRB */
+			i = ((cell2 + 2) % 3) * 2;
+			i += (cell1 < cell3) ^ (cell2 == LIBFONTS_SUBPIXEL_COLOUR_GREEN);
+			*orderp = i * 2 + (layout == LIBFONTS_SUBPIXEL_ORDER_CLASS_1_2_3) + LIBFONTS_SUBPIXEL_ORDER_RGB;
+		}
+		return 1;
+
+	} else if (layout >= LIBFONTS_SUBPIXEL_ORDER_CLASS_11_23 || layout <= LIBFONTS_SUBPIXEL_ORDER_CLASS_BALANCED_13_12) {
+		if (orderp) {
+			/* RGB, RBG, GRB, GBR, BRG, BGR */
+			i = (cell1 * 2) + (cell2 > cell3);
+			*orderp = i * 4 + (layout - LIBFONTS_SUBPIXEL_ORDER_CLASS_11_23) % 4 + LIBFONTS_SUBPIXEL_ORDER_RR_GB;
+			*orderp = (layout >= LIBFONTS_SUBPIXEL_ORDER_CLASS_BALANCED_11_23) * 24;
+		}
+		return 1;
+
+	} else {
+		errno = EINVAL;
+		return -1;
+	}
+}