Add some functions needed fore encoding LSS16 files

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

1 files changed, 46 insertions, 0 deletions

diff --git a/liblss16_encoder_init.c b/liblss16_encoder_init.c
new file mode 100644
index 0000000..037cd8e
--- /dev/null
+++ b/liblss16_encoder_init.c
@@ -0,0 +1,46 @@
+/* See LICENSE file for copyright and license details. */
+#include "liblss16.h"
+#include <string.h>
+
+
+int
+liblss16_encoder_init(struct liblss16_encoder *encoder, const struct liblss16_header *header,
+		      int rgb6, enum liblss16_encode_error *error_out)
+{
+	int i;
+
+	memset(encoder, 0, sizeof(*encoder));
+	memcpy(&encoder->header, header, sizeof(*header));
+
+	if (!encoder->header.width || !encoder->header.height || encoder->header.height >> 15) {
+		if (error_out)
+			*error_out = LIBLSS16_ENCODE_BAD_IMAGE_SIZE;
+		return -1;
+	}
+
+	if (rgb6) {
+		uint8_t or = 0;
+		for (i = 0; i < 16; i++) {
+			or |= encoder->header.colour_map[i].r;
+			or |= encoder->header.colour_map[i].g;
+			or |= encoder->header.colour_map[i].b;
+		}
+		if (or & 0xC0) {
+			if (error_out)
+				*error_out = LIBLSS16_ENCODE_BAD_COLOUR;
+			return -1;
+		}
+	} else {
+		struct liblss16_colour *map = encoder->header.colour_map;
+		for (i = 0; i < 16; i++) {
+			map[i].r = (uint8_t)(((unsigned)map[i].r * 63U + 127U) / 255U);
+			map[i].g = (uint8_t)(((unsigned)map[i].g * 63U + 127U) / 255U);
+			map[i].b = (uint8_t)(((unsigned)map[i].b * 63U + 127U) / 255U);
+		}
+	}
+
+	encoder->x_rem = encoder->header.width;
+	encoder->y_rem = encoder->header.height;
+
+	return 0;
+}