Add palette object. Optimise matching colour in case where we chose the palette. In other cases, we still have to seach all the colours, but that doesn't ever seem to be used.

1 files changed, 111 insertions, 0 deletions

diff --git a/include/palette.h b/include/palette.h
new file mode 100644
index 0000000..845c1bc
--- /dev/null
+++ b/include/palette.h
@@ -0,0 +1,111 @@
+/*
+ * Copyright 2012 Michael Drake <tlsa@netsurf-browser.org>
+ *
+ * This file is part of libnsfb, http://www.netsurf-browser.org/
+ * Licenced under the MIT License,
+ *                http://www.opensource.org/licenses/mit-license.php
+ *
+ * This is the *internal* interface for the cursor. 
+ */
+
+#ifndef PALETTE_H
+#define PALETTE_H 1
+
+#include <stdint.h>
+#include <limits.h>
+
+#include "libnsfb.h"
+#include "libnsfb_plot.h"
+
+enum nsfb_palette_type_e {
+	NSFB_PALETTE_EMPTY,     /**< empty palette object */
+	NSFB_PALETTE_NSFB_8BPP, /**< libnsfb's own 8bpp palette */
+	NSFB_PALETTE_OTHER      /**< any other palette  */
+};
+
+struct nsfb_palette_s {
+	enum nsfb_palette_type_e type; /**< Palette type */
+	uint8_t last; /**< Last used palette index */
+	nsfb_colour_t data[256]; /**< Palette for index modes */
+};
+
+/** Create an empty palette object. */
+bool nsfb_palette_new(struct nsfb_palette_s **palette);
+
+/** Free a palette object. */
+void nsfb_palette_free(struct nsfb_palette_s *palette);
+
+/** Generate libnsfb 8bpp default palette. */
+void nsfb_palette_generate_nsfb_8bpp(struct nsfb_palette_s *palette);
+
+
+static inline uint8_t nsfb_palette_best_match(
+		const struct nsfb_palette_s *palette,
+		nsfb_colour_t c)
+{
+	uint8_t best_col = 0;
+
+	nsfb_colour_t palent;
+	int col;
+	int dr, dg, db; /* delta red, green blue values */
+
+	int cur_distance;
+	int best_distance = INT_MAX;
+
+	switch (palette->type) {
+	case NSFB_PALETTE_NSFB_8BPP:
+		/* Index into colour cube part */
+		dr = ((( c        & 0xFF) * 5) + 128) / 256;
+		dg = ((((c >>  8) & 0xFF) * 7) + 128) / 256;
+		db = ((((c >> 16) & 0xFF) * 4) + 128) / 256;
+		col = 40 * dr + 5 * dg + db;
+
+		palent = palette->data[col];
+		dr = ( c        & 0xFF) - ( palent        & 0xFF);
+		dg = ((c >>  8) & 0xFF) - ((palent >> 8 ) & 0xFF);
+		db = ((c >> 16) & 0xFF) - ((palent >> 16) & 0xFF);
+		cur_distance = (dr * dr) + (dg * dg) + (db * db);
+
+		best_col = col;
+		best_distance = cur_distance;
+
+		/* Index into grayscale part */
+		col = (( c        & 0xFF) +
+		       ((c >>  8) & 0xFF) +
+		       ((c >> 16) & 0xFF) + (45 / 2)) / (15 * 3) - 1 + 240;
+		palent = palette->data[col];
+
+		dr = ( c        & 0xFF) - ( palent        & 0xFF);
+		dg = ((c >>  8) & 0xFF) - ((palent >>  8) & 0xFF);
+		db = ((c >> 16) & 0xFF) - ((palent >> 16) & 0xFF);
+		cur_distance = (dr * dr) + (dg * dg) + (db * db);
+		if (cur_distance < best_distance) {
+			best_distance = cur_distance;
+			best_col = col;
+		}
+		break;
+
+	case NSFB_PALETTE_OTHER:
+		/* Try all colours in palette */
+		for (col = 0; col <= palette->last; col++) {
+			palent = palette->data[col];
+
+			dr = ( c        & 0xFF) - ( palent        & 0xFF);
+			dg = ((c >>  8) & 0xFF) - ((palent >>  8) & 0xFF);
+			db = ((c >> 16) & 0xFF) - ((palent >> 16) & 0xFF);
+			cur_distance = (dr * dr) + (dg * dg) + (db * db);
+			if (cur_distance < best_distance) {
+				best_distance = cur_distance;
+				best_col = col;
+			}
+		}
+		break;
+
+	default:
+		break;
+	}
+
+        return best_col;
+}
+
+#endif /* PALETTE_H */