diff --git a/zrle.c b/zrle.c
new file mode 100644
index 0000000..6d66fe6
--- /dev/null
+++ b/zrle.c
@@ -0,0 +1,126 @@
+#include "rfb-proto.h"
+
+#include <stdint.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <endian.h>
+#include <assert.h>
+#include <zlib.h>
+
+#define POPCOUNT(x) __builtin_popcount(x)
+
+void pixel_format_into_native(struct rfb_pixel_format *fmt)
+{
+#if __BYTE_ORDER__ == __LITTLE_ENDIAN__
+	if (!fmt->big_endian_flag)
+		return;
+
+	fmt->big_endian_flag = 0;
+#else
+	if (fmt->big_endian_flag)
+		return;
+
+	fmt->big_endian_flag = 1;
+#endif
+
+	fmt->red_shift = fmt->bits_per_pixel - fmt->red_shift;
+	fmt->green_shift = fmt->bits_per_pixel - fmt->green_shift;
+	fmt->blue_shift = fmt->bits_per_pixel - fmt->blue_shift;
+}
+
+void pixel32_to_cpixel(uint8_t *restrict dst,
+		       const struct rfb_pixel_format* dst_fmt,
+		       const uint32_t *restrict src,
+		       const struct rfb_pixel_format* src_fmt,
+		       size_t bytes_per_cpixel, size_t len)
+{
+	assert(dst_fmt->true_colour_flag);
+	assert(dst_fmt->bits_per_pixel <= 32);
+	assert(dst_fmt->depth <= 24);
+	assert(bytes_per_cpixel <= 3 && bytes_per_cpixel >= 1);
+
+	uint32_t src_red_shift = src_fmt->red_shift;
+	uint32_t src_green_shift = src_fmt->green_shift;
+	uint32_t src_blue_shift = src_fmt->blue_shift;
+
+	uint32_t dst_red_shift = dst_fmt->red_shift;
+	uint32_t dst_green_shift = dst_fmt->green_shift;
+	uint32_t dst_blue_shift = dst_fmt->blue_shift;
+
+	uint32_t src_red_max = src_fmt->red_max;
+	uint32_t src_green_max = src_fmt->green_max;
+	uint32_t src_blue_max = src_fmt->blue_max;
+
+	uint32_t dst_red_max = dst_fmt->red_max;
+	uint32_t dst_green_max = dst_fmt->green_max;
+	uint32_t dst_blue_max = dst_fmt->blue_max;
+
+	uint32_t src_red_bits = POPCOUNT(src_fmt->red_max);
+	uint32_t src_green_bits = POPCOUNT(src_fmt->green_max);
+	uint32_t src_blue_bits = POPCOUNT(src_fmt->blue_max);
+
+	uint32_t dst_red_bits = POPCOUNT(dst_fmt->red_max);
+	uint32_t dst_green_bits = POPCOUNT(dst_fmt->green_max);
+	uint32_t dst_blue_bits = POPCOUNT(dst_fmt->blue_max);
+
+	uint32_t dst_endian_correction;
+
+#define CONVERT_PIXELS(cpx, px) \
+	{ \
+		uint32_t r, g, b; \
+		r = ((px >> src_red_shift) & src_red_max) << dst_red_bits \
+			>> src_red_bits << dst_red_shift; \
+		g = ((px >> src_green_shift) & src_green_max) << dst_green_bits \
+			>> src_green_bits << dst_green_shift; \
+		b = ((px >> src_blue_shift) & src_blue_max) << dst_blue_bits \
+			>> src_blue_bits << dst_blue_shift; \
+		cpx = r | g | b; \
+	}
+
+	switch (bytes_per_cpixel) {
+	case 3:
+		dst_endian_correction = dst_fmt->big_endian_flag ? 16 : 0;
+
+		while (len--) {
+			uint32_t cpx, px = *src++;
+
+			CONVERT_PIXELS(cpx, px)
+
+			*dst++ = (cpx >> (0 ^ dst_endian_correction)) & 0xff;
+			*dst++ = (cpx >> 8) & 0xff;
+			*dst++ = (cpx >> (16 ^ dst_endian_correction)) & 0xff;
+		}
+		break;
+	case 2:
+		dst_endian_correction = dst_fmt->big_endian_flag ? 8 : 0;
+
+		while (len--) {
+			uint32_t cpx, px = *src++;
+
+			CONVERT_PIXELS(cpx, px)
+
+			*dst++ = (cpx >> (0 ^ dst_endian_correction)) & 0xff;
+			*dst++ = (cpx >> (8 ^ dst_endian_correction)) & 0xff;
+		}
+		break;
+	case 1:
+		while (len--) {
+			uint32_t cpx, px = *src++;
+
+			CONVERT_PIXELS(cpx, px)
+
+			*dst++ = cpx & 0xff;
+		}
+		break;
+	default:
+		abort();
+	}
+
+#undef CONVERT_PIXELS
+}
+
+void zrle_encode_tile(uint8_t* dst, const uint32_t *src, int stride,
+		      int width, int height)
+{
+
+}