Add SIXEL graphics support for suckless st. (sixel.c/sixel_hls.c come from mintty, licensed under GPL)

suckless-st-sixel.diff

commit ea830e03d4d4562b1ff225940f65bceddd9cad6c
Author: Hayaki Saito <saitoha@me.com>
Date:   Sun Jun 11 23:46:45 2017 +0900

    Add sixel graphics support
    
    Signed-off-by: Hayaki Saito <saitoha@me.com>

diff --git a/Makefile b/Makefile
index d8595fe..a25d040 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@
 
 include config.mk
 
-SRC = st.c x.c
+SRC = st.c x.c sixel.c sixel_hls.c
 OBJ = ${SRC:.c=.o}
 
 all: options st
diff --git a/sixel.c b/sixel.c
new file mode 100644
index 0000000..7bfe598
--- /dev/null
+++ b/sixel.c
@@ -0,0 +1,616 @@
+// sixel.c (part of mintty)
+// originally written by kmiya@cluti (https://github.com/saitoha/sixel/blob/master/fromsixel.c)
+// Licensed under the terms of the GNU General Public License v3 or later.
+
+#include <stdlib.h>
+#include <string.h>  /* memcpy */
+
+#include "sixel.h"
+#include "sixel_hls.h"
+
+#define SIXEL_RGB(r, g, b) ((r) + ((g) << 8) +  ((b) << 16))
+#define SIXEL_PALVAL(n,a,m) (((n) * (a) + ((m) / 2)) / (m))
+#define SIXEL_XRGB(r,g,b) SIXEL_RGB(SIXEL_PALVAL(r, 255, 100), SIXEL_PALVAL(g, 255, 100), SIXEL_PALVAL(b, 255, 100))
+
+static sixel_color_t const sixel_default_color_table[] = {
+	SIXEL_XRGB( 0,  0,  0),  /*  0 Black    */
+	SIXEL_XRGB(20, 20, 80),  /*  1 Blue     */
+	SIXEL_XRGB(80, 13, 13),  /*  2 Red      */
+	SIXEL_XRGB(20, 80, 20),  /*  3 Green    */
+	SIXEL_XRGB(80, 20, 80),  /*  4 Magenta  */
+	SIXEL_XRGB(20, 80, 80),  /*  5 Cyan     */
+	SIXEL_XRGB(80, 80, 20),  /*  6 Yellow   */
+	SIXEL_XRGB(53, 53, 53),  /*  7 Gray 50% */
+	SIXEL_XRGB(26, 26, 26),  /*  8 Gray 25% */
+	SIXEL_XRGB(33, 33, 60),  /*  9 Blue*    */
+	SIXEL_XRGB(60, 26, 26),  /* 10 Red*     */
+	SIXEL_XRGB(33, 60, 33),  /* 11 Green*   */
+	SIXEL_XRGB(60, 33, 60),  /* 12 Magenta* */
+	SIXEL_XRGB(33, 60, 60),  /* 13 Cyan*    */
+	SIXEL_XRGB(60, 60, 33),  /* 14 Yellow*  */
+	SIXEL_XRGB(80, 80, 80),  /* 15 Gray 75% */
+};
+
+static int
+set_default_color(sixel_image_t *image)
+{
+	int i;
+	int n;
+	int r;
+	int g;
+	int b;
+
+	/* palette initialization */
+	for (n = 1; n < 17; n++) {
+		image->palette[n] = sixel_default_color_table[n - 1];
+	}
+
+	/* colors 17-232 are a 6x6x6 color cube */
+	for (r = 0; r < 6; r++) {
+		for (g = 0; g < 6; g++) {
+			for (b = 0; b < 6; b++) {
+				image->palette[n++] = SIXEL_RGB(r * 51, g * 51, b * 51);
+			}
+		}
+	}
+
+	/* colors 233-256 are a grayscale ramp, intentionally leaving out */
+	for (i = 0; i < 24; i++) {
+		image->palette[n++] = SIXEL_RGB(i * 11, i * 11, i * 11);
+	}
+
+	for (; n < DECSIXEL_PALETTE_MAX; n++) {
+		image->palette[n] = SIXEL_RGB(255, 255, 255);
+	}
+
+	return (0);
+}
+
+static int
+sixel_image_init(
+    sixel_image_t    *image,
+    int              width,
+    int              height,
+    int              fgcolor,
+    int              bgcolor,
+    int              use_private_register)
+{
+	int status = (-1);
+	size_t size;
+
+	size = (size_t)(width * height) * sizeof(sixel_color_no_t);
+	image->width = width;
+	image->height = height;
+	image->data = (sixel_color_no_t *)malloc(size);
+	image->ncolors = 2;
+	image->use_private_register = use_private_register;
+
+	if (image->data == NULL) {
+		status = (-1);
+		goto end;
+	}
+	memset(image->data, 0, size);
+
+	image->palette[0] = bgcolor;
+
+	if (image->use_private_register)
+		image->palette[1] = fgcolor;
+
+	image->palette_modified = 0;
+
+	status = (0);
+
+end:
+	return status;
+}
+
+
+static int
+image_buffer_resize(
+    sixel_image_t   *image,
+    int              width,
+    int              height)
+{
+	int status = (-1);
+	size_t size;
+	sixel_color_no_t *alt_buffer;
+	int n;
+	int min_height;
+
+	size = (size_t)(width * height) * sizeof(sixel_color_no_t);
+	alt_buffer = (sixel_color_no_t *)malloc(size);
+	if (alt_buffer == NULL) {
+		/* free source image */
+		free(image->data);
+		image->data = NULL;
+		status = (-1);
+		goto end;
+	}
+
+	min_height = height > image->height ? image->height: height;
+	if (width > image->width) {  /* if width is extended */
+		for (n = 0; n < min_height; ++n) {
+			/* copy from source image */
+			memcpy(alt_buffer + width * n,
+			       image->data + image->width * n,
+			       (size_t)image->width * sizeof(sixel_color_no_t));
+			/* fill extended area with background color */
+			memset(alt_buffer + width * n + image->width,
+			       0,
+			       (size_t)(width - image->width) * sizeof(sixel_color_no_t));
+		}
+	} else {
+		for (n = 0; n < min_height; ++n) {
+			/* copy from source image */
+			memcpy(alt_buffer + width * n,
+			       image->data + image->width * n,
+			       (size_t)width * sizeof(sixel_color_no_t));
+		}
+	}
+
+	if (height > image->height) {  /* if height is extended */
+		/* fill extended area with background color */
+		memset(alt_buffer + width * image->height,
+		       0,
+		       (size_t)(width * (height - image->height)) * sizeof(sixel_color_no_t));
+	}
+
+	/* free source image */
+	free(image->data);
+
+	image->data = alt_buffer;
+	image->width = width;
+	image->height = height;
+
+	status = (0);
+
+end:
+	return status;
+}
+
+static void
+sixel_image_deinit(sixel_image_t *image)
+{
+	free(image->data);
+	image->data = NULL;
+}
+
+int
+sixel_parser_init(sixel_state_t *st,
+                  sixel_color_t fgcolor, sixel_color_t bgcolor,
+                  unsigned char use_private_register,
+                  int cell_width, int cell_height)
+{
+	int status = (-1);
+
+	st->state = PS_DECSIXEL;
+	st->pos_x = 0;
+	st->pos_y = 0;
+	st->max_x = 0;
+	st->max_y = 0;
+	st->attributed_pan = 2;
+	st->attributed_pad = 1;
+	st->attributed_ph = 0;
+	st->attributed_pv = 0;
+	st->repeat_count = 1;
+	st->color_index = 16;
+	st->grid_width = cell_width;
+	st->grid_height = cell_height;
+	st->nparams = 0;
+	st->param = 0;
+
+	/* buffer initialization */
+	status = sixel_image_init(&st->image, 1, 1, fgcolor, bgcolor, use_private_register);
+
+	return status;
+}
+
+int
+sixel_parser_set_default_color(sixel_state_t *st)
+{
+	return set_default_color(&st->image);
+}
+
+int
+sixel_parser_finalize(sixel_state_t *st, unsigned char *pixels)
+{
+	int status = (-1);
+	int sx;
+	int sy;
+	sixel_image_t *image = &st->image;
+	int x, y;
+	sixel_color_no_t *src;
+	unsigned char *dst;
+	int color;
+
+	if (++st->max_x < st->attributed_ph)
+		st->max_x = st->attributed_ph;
+
+	if (++st->max_y < st->attributed_pv)
+		st->max_y = st->attributed_pv;
+
+	sx = (st->max_x + st->grid_width - 1) / st->grid_width * st->grid_width;
+	sy = (st->max_y + st->grid_height - 1) / st->grid_height * st->grid_height;
+
+	if (image->width > sx || image->height > sy) {
+		status = image_buffer_resize(image, sx, sy);
+		if (status < 0)
+			goto end;
+	}
+
+	if (image->use_private_register && image->ncolors > 2 && !image->palette_modified) {
+		status = set_default_color(image);
+		if (status < 0)
+			goto end;
+	}
+
+	src = st->image.data;
+	dst = pixels;
+	for (y = 0; y < st->image.height; ++y) {
+		for (x = 0; x < st->image.width; ++x) {
+			color = st->image.palette[*src++];
+			*dst++ = color >> 16 & 0xff;   /* b */
+			*dst++ = color >> 8 & 0xff;    /* g */
+			*dst++ = color >> 0 & 0xff;    /* r */
+			dst++;                         /* a */
+		}
+		/* fill right padding with bgcolor */
+		for (; x < st->image.width; ++x) {
+			color = st->image.palette[0];  /* bgcolor */
+			*dst++ = color >> 16 & 0xff;   /* b */
+			*dst++ = color >> 8 & 0xff;    /* g */
+			*dst++ = color >> 0 & 0xff;    /* r */
+			dst++;                         /* a */
+		}
+	}
+	/* fill bottom padding with bgcolor */
+	for (; y < st->image.height; ++y) {
+		for (x = 0; x < st->image.width; ++x) {
+			color = st->image.palette[0];  /* bgcolor */
+			*dst++ = color >> 16 & 0xff;   /* b */
+			*dst++ = color >> 8 & 0xff;    /* g */
+			*dst++ = color >> 0 & 0xff;    /* r */
+			dst++;                         /* a */
+		}
+	}
+
+	status = (0);
+
+end:
+	return status;
+}
+
+/* convert sixel data into indexed pixel bytes and palette data */
+int
+sixel_parser_parse(sixel_state_t *st, unsigned char *p, size_t len)
+{
+	int status = (-1);
+	int n;
+	int i;
+	int x;
+	int y;
+	int bits;
+	int sixel_vertical_mask;
+	int sx;
+	int sy;
+	int c;
+	int pos;
+	unsigned char *p0 = p;
+	sixel_image_t *image = &st->image;
+
+	if (! image->data)
+		goto end;
+
+	while (p < p0 + len) {
+		switch (st->state) {
+		case PS_ESC:
+			goto end;
+
+		case PS_DECSIXEL:
+			switch (*p) {
+			case '\x1b':
+				st->state = PS_ESC;
+				p++;
+				break;
+			case '"':
+				st->param = 0;
+				st->nparams = 0;
+				st->state = PS_DECGRA;
+				p++;
+				break;
+			case '!':
+				st->param = 0;
+				st->nparams = 0;
+				st->state = PS_DECGRI;
+				p++;
+				break;
+			case '#':
+				st->param = 0;
+				st->nparams = 0;
+				st->state = PS_DECGCI;
+				p++;
+				break;
+			case '$':
+				/* DECGCR Graphics Carriage Return */
+				st->pos_x = 0;
+				p++;
+				break;
+			case '-':
+				/* DECGNL Graphics Next Line */
+				st->pos_x = 0;
+				if (st->pos_y < DECSIXEL_HEIGHT_MAX - 5 - 6)
+					st->pos_y += 6;
+				else
+					st->pos_y = DECSIXEL_HEIGHT_MAX + 1;
+				p++;
+				break;
+			default:
+				if (*p >= '?' && *p <= '~') {  /* sixel characters */
+					if ((image->width < (st->pos_x + st->repeat_count) || image->height < (st->pos_y + 6))
+					        && image->width < DECSIXEL_WIDTH_MAX && image->height < DECSIXEL_HEIGHT_MAX) {
+						sx = image->width * 2;
+						sy = image->height * 2;
+						while (sx < (st->pos_x + st->repeat_count) || sy < (st->pos_y + 6)) {
+							sx *= 2;
+							sy *= 2;
+						}
+
+						if (sx > DECSIXEL_WIDTH_MAX)
+							sx = DECSIXEL_WIDTH_MAX;
+						if (sy > DECSIXEL_HEIGHT_MAX)
+							sy = DECSIXEL_HEIGHT_MAX;
+
+						status = image_buffer_resize(image, sx, sy);
+						if (status < 0)
+							goto end;
+					}
+
+					if (st->color_index > image->ncolors)
+						image->ncolors = st->color_index;
+
+					if (st->pos_x + st->repeat_count > image->width)
+						st->repeat_count = image->width - st->pos_x;
+
+					if (st->repeat_count > 0 && st->pos_y - 5 < image->height) {
+						bits = *p - '?';
+						if (bits != 0) {
+							sixel_vertical_mask = 0x01;
+							if (st->repeat_count <= 1) {
+								for (i = 0; i < 6; i++) {
+									if ((bits & sixel_vertical_mask) != 0) {
+										pos = image->width * (st->pos_y + i) + st->pos_x;
+										image->data[pos] = st->color_index;
+										if (st->max_x < st->pos_x)
+											st->max_x = st->pos_x;
+										if (st->max_y < (st->pos_y + i))
+											st->max_y = st->pos_y + i;
+									}
+									sixel_vertical_mask <<= 1;
+								}
+							} else {
+								/* st->repeat_count > 1 */
+								for (i = 0; i < 6; i++) {
+									if ((bits & sixel_vertical_mask) != 0) {
+										c = sixel_vertical_mask << 1;
+										for (n = 1; (i + n) < 6; n++) {
+											if ((bits & c) == 0)
+												break;
+											c <<= 1;
+										}
+										for (y = st->pos_y + i; y < st->pos_y + i + n; ++y) {
+											for (x = st->pos_x; x < st->pos_x + st->repeat_count; ++x)
+												image->data[image->width * y + x] = st->color_index;
+										}
+										if (st->max_x < (st->pos_x + st->repeat_count - 1))
+											st->max_x = st->pos_x + st->repeat_count - 1;
+										if (st->max_y < (st->pos_y + i + n - 1))
+											st->max_y = st->pos_y + i + n - 1;
+										i += (n - 1);
+										sixel_vertical_mask <<= (n - 1);
+									}
+									sixel_vertical_mask <<= 1;
+								}
+							}
+						}
+					}
+					if (st->repeat_count > 0)
+						st->pos_x += st->repeat_count;
+					st->repeat_count = 1;
+				}
+				p++;
+				break;
+			}
+			break;
+
+		case PS_DECGRA:
+			/* DECGRA Set Raster Attributes " Pan; Pad; Ph; Pv */
+			switch (*p) {
+			case '\x1b':
+				st->state = PS_ESC;
+				p++;
+				break;
+			case '0':
+			case '1':
+			case '2':
+			case '3':
+			case '4':
+			case '5':
+			case '6':
+			case '7':
+			case '8':
+			case '9':
+				st->param = st->param * 10 + *p - '0';
+				if (st->param > DECSIXEL_PARAMVALUE_MAX)
+					st->param = DECSIXEL_PARAMVALUE_MAX;
+				p++;
+				break;
+			case ';':
+				if (st->nparams < DECSIXEL_PARAMS_MAX)
+					st->params[st->nparams++] = st->param;
+				st->param = 0;
+				p++;
+				break;
+			default:
+				if (st->nparams < DECSIXEL_PARAMS_MAX)
+					st->params[st->nparams++] = st->param;
+				if (st->nparams > 0)
+					st->attributed_pad = st->params[0];
+				if (st->nparams > 1)
+					st->attributed_pan = st->params[1];
+				if (st->nparams > 2 && st->params[2] > 0)
+					st->attributed_ph = st->params[2];
+				if (st->nparams > 3 && st->params[3] > 0)
+					st->attributed_pv = st->params[3];
+
+				if (st->attributed_pan <= 0)
+					st->attributed_pan = 1;
+				if (st->attributed_pad <= 0)
+					st->attributed_pad = 1;
+
+				if (image->width < st->attributed_ph ||
+				        image->height < st->attributed_pv) {
+					sx = st->attributed_ph;
+					if (image->width > st->attributed_ph)
+						sx = image->width;
+
+					sy = st->attributed_pv;
+					if (image->height > st->attributed_pv)
+						sy = image->height;
+
+					sx = (sx + st->grid_width - 1) / st->grid_width * st->grid_width;
+					sy = (sy + st->grid_height - 1) / st->grid_height * st->grid_height;
+
+					if (sx > DECSIXEL_WIDTH_MAX)
+						sx = DECSIXEL_WIDTH_MAX;
+					if (sy > DECSIXEL_HEIGHT_MAX)
+						sy = DECSIXEL_HEIGHT_MAX;
+
+					status = image_buffer_resize(image, sx, sy);
+					if (status < 0)
+						goto end;
+				}
+				st->state = PS_DECSIXEL;
+				st->param = 0;
+				st->nparams = 0;
+			}
+			break;
+
+		case PS_DECGRI:
+			/* DECGRI Graphics Repeat Introducer ! Pn Ch */
+			switch (*p) {
+			case '\x1b':
+				st->state = PS_ESC;
+				p++;
+				break;
+			case '0':
+			case '1':
+			case '2':
+			case '3':
+			case '4':
+			case '5':
+			case '6':
+			case '7':
+			case '8':
+			case '9':
+				st->param = st->param * 10 + *p - '0';
+				if (st->param > DECSIXEL_PARAMVALUE_MAX)
+					st->param = DECSIXEL_PARAMVALUE_MAX;
+				p++;
+				break;
+			default:
+				st->repeat_count = st->param;
+				if (st->repeat_count == 0)
+					st->repeat_count = 1;
+				st->state = PS_DECSIXEL;
+				st->param = 0;
+				st->nparams = 0;
+				break;
+			}
+			break;
+
+		case PS_DECGCI:
+			/* DECGCI Graphics Color Introducer # Pc; Pu; Px; Py; Pz */
+			switch (*p) {
+			case '\x1b':
+				st->state = PS_ESC;
+				p++;
+				break;
+			case '0':
+			case '1':
+			case '2':
+			case '3':
+			case '4':
+			case '5':
+			case '6':
+			case '7':
+			case '8':
+			case '9':
+				st->param = st->param * 10 + *p - '0';
+				if (st->param > DECSIXEL_PARAMVALUE_MAX)
+					st->param = DECSIXEL_PARAMVALUE_MAX;
+				p++;
+				break;
+			case ';':
+				if (st->nparams < DECSIXEL_PARAMS_MAX)
+					st->params[st->nparams++] = st->param;
+				st->param = 0;
+				p++;
+				break;
+			default:
+				st->state = PS_DECSIXEL;
+				if (st->nparams < DECSIXEL_PARAMS_MAX)
+					st->params[st->nparams++] = st->param;
+				st->param = 0;
+
+				if (st->nparams > 0) {
+					st->color_index = 1 + st->params[0];  /* offset 1(background color) added */
+					if (st->color_index < 0)
+						st->color_index = 0;
+					else if (st->color_index >= DECSIXEL_PALETTE_MAX)
+						st->color_index = DECSIXEL_PALETTE_MAX - 1;
+				}
+
+				if (st->nparams > 4) {
+					st->image.palette_modified = 1;
+					if (st->params[1] == 1) {
+						/* HLS */
+						if (st->params[2] > 360)
+							st->params[2] = 360;
+						if (st->params[3] > 100)
+							st->params[3] = 100;
+						if (st->params[4] > 100)
+							st->params[4] = 100;
+						image->palette[st->color_index]
+						    = hls_to_rgb(st->params[2], st->params[3], st->params[4]);
+					} else if (st->params[1] == 2) {
+						/* RGB */
+						if (st->params[2] > 100)
+							st->params[2] = 100;
+						if (st->params[3] > 100)
+							st->params[3] = 100;
+						if (st->params[4] > 100)
+							st->params[4] = 100;
+						image->palette[st->color_index]
+						    = SIXEL_XRGB(st->params[2], st->params[3], st->params[4]);
+					}
+				}
+				break;
+			}
+			break;
+		default:
+			break;
+		}
+	}
+
+	status = (0);
+
+end:
+	return status;
+}
+
+void
+sixel_parser_deinit(sixel_state_t *st)
+{
+	if (st)
+		sixel_image_deinit(&st->image);
+}
diff --git a/sixel.h b/sixel.h
new file mode 100644
index 0000000..8a05c44
--- /dev/null
+++ b/sixel.h
@@ -0,0 +1,58 @@
+#ifndef SIXEL_H
+#define SIXEL_H
+
+#define DECSIXEL_PARAMS_MAX 16
+#define DECSIXEL_PALETTE_MAX 1024
+#define DECSIXEL_PARAMVALUE_MAX 65535
+#define DECSIXEL_WIDTH_MAX 4096
+#define DECSIXEL_HEIGHT_MAX 4096
+
+typedef unsigned short sixel_color_no_t;
+typedef unsigned int sixel_color_t;
+
+typedef struct sixel_image_buffer {
+	sixel_color_no_t *data;
+	int width;
+	int height;
+	sixel_color_t palette[DECSIXEL_PALETTE_MAX];
+	sixel_color_no_t ncolors;
+	int palette_modified;
+	int use_private_register;
+} sixel_image_t;
+
+typedef enum parse_state {
+	PS_ESC        = 1,  /* ESC */
+	PS_DECSIXEL   = 2,  /* DECSIXEL body part ", $, -, ? ... ~ */
+	PS_DECGRA     = 3,  /* DECGRA Set Raster Attributes " Pan; Pad; Ph; Pv */
+	PS_DECGRI     = 4,  /* DECGRI Graphics Repeat Introducer ! Pn Ch */
+	PS_DECGCI     = 5,  /* DECGCI Graphics Color Introducer # Pc; Pu; Px; Py; Pz */
+} parse_state_t;
+
+typedef struct parser_context {
+	parse_state_t state;
+	int pos_x;
+	int pos_y;
+	int max_x;
+	int max_y;
+	int attributed_pan;
+	int attributed_pad;
+	int attributed_ph;
+	int attributed_pv;
+	int repeat_count;
+	int color_index;
+	int bgindex;
+	int grid_width;
+	int grid_height;
+	int param;
+	int nparams;
+	int params[DECSIXEL_PARAMS_MAX];
+	sixel_image_t image;
+} sixel_state_t;
+
+int sixel_parser_init(sixel_state_t *st, sixel_color_t fgcolor, sixel_color_t bgcolor, unsigned char use_private_register, int cell_width, int cell_height);
+int sixel_parser_parse(sixel_state_t *st, unsigned char *p, size_t len);
+int sixel_parser_set_default_color(sixel_state_t *st);
+int sixel_parser_finalize(sixel_state_t *st, unsigned char *pixels);
+void sixel_parser_deinit(sixel_state_t *st);
+
+#endif
diff --git a/sixel_hls.c b/sixel_hls.c
new file mode 100644
index 0000000..4f157b2
--- /dev/null
+++ b/sixel_hls.c
@@ -0,0 +1,115 @@
+// sixel.c (part of mintty)
+// this function is derived from a part of graphics.c
+// in Xterm pl#310 originally written by Ross Combs.
+//
+// Copyright 2013,2014 by Ross Combs
+//
+//                         All Rights Reserved
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+// IN NO EVENT SHALL THE ABOVE LISTED COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
+// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+// Except as contained in this notice, the name(s) of the above copyright
+// holders shall not be used in advertising or otherwise to promote the
+// sale, use or other dealings in this Software without prior written
+// authorization.
+
+#define SIXEL_RGB(r, g, b) (((r) << 16) + ((g) << 8) +  (b))
+
+int
+hls_to_rgb(int hue, int lum, int sat)
+{
+  double hs = (hue + 240) % 360;
+  double hv = hs / 360.0;
+  double lv = lum / 100.0;
+  double sv = sat / 100.0;
+  double c, x, m, c2;
+  double r1, g1, b1;
+  int r, g, b;
+  int hpi;
+
+  if (sat == 0) {
+    r = g = b = lum * 255 / 100;
+    return SIXEL_RGB(r, g, b);
+  }
+
+  if ((c2 = ((2.0 * lv) - 1.0)) < 0.0) {
+    c2 = -c2;
+  }
+  c = (1.0 - c2) * sv;
+  hpi = (int) (hv * 6.0);
+  x = (hpi & 1) ? c : 0.0;
+  m = lv - 0.5 * c;
+
+  switch (hpi) {
+  case 0:
+    r1 = c;
+    g1 = x;
+    b1 = 0.0;
+    break;
+  case 1:
+    r1 = x;
+    g1 = c;
+    b1 = 0.0;
+    break;
+  case 2:
+    r1 = 0.0;
+    g1 = c;
+    b1 = x;
+    break;
+  case 3:
+    r1 = 0.0;
+    g1 = x;
+    b1 = c;
+    break;
+  case 4:
+    r1 = x;
+    g1 = 0.0;
+    b1 = c;
+    break;
+  case 5:
+    r1 = c;
+    g1 = 0.0;
+    b1 = x;
+    break;
+  default:
+    return SIXEL_RGB(255, 255, 255);
+  }
+
+  r = (int) ((r1 + m) * 100.0 + 0.5);
+  g = (int) ((g1 + m) * 100.0 + 0.5);
+  b = (int) ((b1 + m) * 100.0 + 0.5);
+
+  if (r < 0) {
+    r = 0;
+  } else if (r > 100) {
+    r = 100;
+  }
+  if (g < 0) {
+    g = 0;
+  } else if (g > 100) {
+    g = 100;
+  }
+  if (b < 0) {
+    b = 0;
+  } else if (b > 100) {
+    b = 100;
+  }
+  return SIXEL_RGB(r * 255 / 100, g * 255 / 100, b * 255 / 100);
+}
diff --git a/sixel_hls.h b/sixel_hls.h
new file mode 100644
index 0000000..6176589
--- /dev/null
+++ b/sixel_hls.h
@@ -0,0 +1,7 @@
+/*
+ * Primary color hues:
+ *  blue:  0 degrees
+ *  red:   120 degrees
+ *  green: 240 degrees
+ */
+int hls_to_rgb(int hue, int lum, int sat);
diff --git a/st.c b/st.c
index 8d4a9f2..7df71d9 100644
--- a/st.c
+++ b/st.c
@@ -35,6 +35,7 @@ char *argv0;
 
 #include "win.h"
 #include "st.h"
+#include "sixel.h"
 
 #if   defined(__linux)
  #include <pty.h>
@@ -147,6 +148,7 @@ static void stty(void);
 static void sigchld(int);
 
 static void csidump(void);
+static void dcshandle(void);
 static void csihandle(void);
 static void csiparse(void);
 static void csireset(void);
@@ -209,6 +211,7 @@ Term term;
 Selection sel;
 int cmdfd;
 pid_t pid;
+sixel_state_t sixel_st;
 char **opt_cmd  = NULL;
 char *opt_class = NULL;
 char *opt_embed = NULL;
@@ -1009,6 +1012,7 @@ void
 treset(void)
 {
 	uint i;
+	ImageList *im;
 
 	term.c = (TCursor){{
 		.mode = ATTR_NULL,
@@ -1031,6 +1035,9 @@ treset(void)
 		tclearregion(0, 0, term.col-1, term.row-1);
 		tswapscreen();
 	}
+
+	for (im = term.images; im; im = im->next)
+		im->should_delete = 1;
 }
 
 void
@@ -1047,9 +1054,12 @@ void
 tswapscreen(void)
 {
 	Line *tmp = term.line;
+	ImageList *im = term.images;
 
 	term.line = term.alt;
 	term.alt = tmp;
+	term.images = term.images_alt;
+	term.images_alt = im;
 	term.mode ^= MODE_ALTSCREEN;
 	tfulldirt();
 }
@@ -1059,6 +1069,7 @@ tscrolldown(int orig, int n)
 {
 	int i;
 	Line temp;
+	ImageList *im;
 
 	LIMIT(n, 0, term.bot-orig+1);
 
@@ -1071,6 +1082,13 @@ tscrolldown(int orig, int n)
 		term.line[i-n] = temp;
 	}
 
+	for (im = term.images; im; im = im->next) {
+		if (im->y < term.bot)
+			im->y += n;
+		if (im->y > term.bot)
+			im->should_delete = 1;
+	}
+
 	selscroll(orig, n);
 }
 
@@ -1079,6 +1097,7 @@ tscrollup(int orig, int n)
 {
 	int i;
 	Line temp;
+	ImageList *im;
 
 	LIMIT(n, 0, term.bot-orig+1);
 
@@ -1091,6 +1110,13 @@ tscrollup(int orig, int n)
 		term.line[i+n] = temp;
 	}
 
+	for (im = term.images; im; im = im->next) {
+		if (im->y+im->height/win.ch > term.top)
+			im->y -= n;
+		if (im->y+im->height/win.ch < term.top)
+			im->should_delete = 1;
+	}
+
 	selscroll(orig, -n);
 }
 
@@ -1609,6 +1635,23 @@ tsetmode(int priv, int set, int *args, int narg)
 }
 
 void
+dcshandle(void)
+{
+	switch (csiescseq.mode[0]) {
+	default:
+		fprintf(stderr, "erresc: unknown csi ");
+		csidump();
+		/* die(""); */
+		break;
+	case 'q': /* DECSIXEL */
+		if (sixel_parser_init(&sixel_st, 0, 0 << 16 | 0 << 8 | 0, 1, win.cw, win.ch) != 0)
+			perror("sixel_parser_init() failed");
+		term.mode |= MODE_SIXEL;
+		break;
+	}
+}
+
+void
 csihandle(void)
 {
 	char buf[40];
@@ -1853,6 +1896,8 @@ strhandle(void)
 {
 	char *p = NULL;
 	int j, narg, par;
+	ImageList *new_image;
+	int i;
 
 	term.esc &= ~(ESC_STR_END|ESC_STR);
 	strparse();
@@ -1903,7 +1948,39 @@ strhandle(void)
 		xsettitle(strescseq.args[0]);
 		return;
 	case 'P': /* DCS -- Device Control String */
-		term.mode |= ESC_DCS;
+		if (IS_SET(MODE_SIXEL)) {
+			term.mode &= ~MODE_SIXEL;
+			new_image = malloc(sizeof(ImageList));
+			memset(new_image, 0, sizeof(ImageList));
+			new_image->x = term.c.x;
+			new_image->y = term.c.y;
+			new_image->width = sixel_st.image.width;
+			new_image->height = sixel_st.image.height;
+			new_image->pixels = malloc(new_image->width * new_image->height * 4);
+			if (sixel_parser_finalize(&sixel_st, new_image->pixels) != 0) {
+				perror("sixel_parser_finalize() failed");
+				sixel_parser_deinit(&sixel_st);
+				return;
+			}
+			sixel_parser_deinit(&sixel_st);
+			if (term.images) {
+				ImageList *im;
+				for (im = term.images; im->next;)
+					im = im->next;
+				im->next = new_image;
+				new_image->prev = im;
+			} else {
+				term.images = new_image;
+			}
+			for (i = 0; i < (sixel_st.image.height + win.ch-1)/win.ch; ++i) {
+				int x;
+				tclearregion(term.c.x, term.c.y, term.c.x+(sixel_st.image.width+win.cw-1)/win.cw, term.c.y);
+				for (x = term.c.x; x < MIN(term.col, term.c.x+(sixel_st.image.width+win.cw-1)/win.cw); x++)
+					term.line[term.c.y][x].mode |= ATTR_SIXEL;
+				tnewline(1);
+			}
+		}
+		return;
 	case '_': /* APC -- Application Program Command */
 	case '^': /* PM -- Privacy Message */
 		return;
@@ -2274,6 +2351,7 @@ eschandle(uchar ascii)
 		term.esc |= ESC_UTF8;
 		return 0;
 	case 'P': /* DCS -- Device Control String */
+		term.esc |= ESC_DCS;
 	case '_': /* APC -- Application Program Command */
 	case '^': /* PM -- Privacy Message */
 	case ']': /* OSC -- Operating System Command */
@@ -2376,22 +2454,18 @@ tputc(Rune u)
 		if (u == '\a' || u == 030 || u == 032 || u == 033 ||
 		   ISCONTROLC1(u)) {
 			term.esc &= ~(ESC_START|ESC_STR|ESC_DCS);
-			if (IS_SET(MODE_SIXEL)) {
-				/* TODO: render sixel */;
-				term.mode &= ~MODE_SIXEL;
-				return;
-			}
 			term.esc |= ESC_STR_END;
 			goto check_control_code;
 		}
 
 
 		if (IS_SET(MODE_SIXEL)) {
-			/* TODO: implement sixel mode */
+			if (sixel_parser_parse(&sixel_st, (unsigned char *)&u, 1) != 0)
+				perror("sixel_parser_parse() failed");
 			return;
 		}
-		if (term.esc&ESC_DCS && strescseq.len == 0 && u == 'q')
-			term.mode |= MODE_SIXEL;
+		if (term.esc & ESC_DCS)
+			goto check_control_code;
 
 		if (strescseq.len+len >= sizeof(strescseq.buf)-1) {
 			/*
@@ -2438,6 +2512,15 @@ check_control_code:
 				csihandle();
 			}
 			return;
+		} else if (term.esc & ESC_DCS) {
+			csiescseq.buf[csiescseq.len++] = u;
+			if (BETWEEN(u, 0x40, 0x7E)
+					|| csiescseq.len >= \
+					sizeof(csiescseq.buf)-1) {
+				csiparse();
+				dcshandle();
+			}
+			return;
 		} else if (term.esc & ESC_UTF8) {
 			tdefutf8(u);
 		} else if (term.esc & ESC_ALTCHARSET) {
diff --git a/st.h b/st.h
index 44d4938..61195be 100644
--- a/st.h
+++ b/st.h
@@ -33,6 +33,7 @@ enum glyph_attribute {
 	ATTR_WRAP       = 1 << 8,
 	ATTR_WIDE       = 1 << 9,
 	ATTR_WDUMMY     = 1 << 10,
+	ATTR_SIXEL      = 1 << 11,
 	ATTR_BOLD_FAINT = ATTR_BOLD | ATTR_FAINT,
 };
 
@@ -108,6 +109,17 @@ typedef struct {
 	char state;
 } TCursor;
 
+typedef struct _ImageList {
+	struct _ImageList *next, *prev;
+	unsigned char *pixels;
+	void *pixmap;
+	int width;
+	int height;
+	int x;
+	int y;
+	int should_delete;
+} ImageList;
+
 /* Internal representation of the screen */
 typedef struct {
 	int row;      /* nb row */
@@ -126,6 +138,8 @@ typedef struct {
 	int icharset; /* selected charset for sequence */
 	int numlock; /* lock numbers in keyboard */
 	int *tabs;
+	ImageList *images;     /* sixel images */
+	ImageList *images_alt; /* sixel images for alternate screen */
 } Term;
 
 /* Purely graphic info */
diff --git a/x.c b/x.c
index fbfd350..38a3da0 100644
--- a/x.c
+++ b/x.c
@@ -16,6 +16,7 @@
 #include <X11/XKBlib.h>
 
 #include "arg.h"
+#include "compat.h"
 
 #define Glyph Glyph_
 #define Font Font_
@@ -1384,14 +1385,101 @@ xsettitle(char *p)
 }
 
 void
+delete_image(ImageList *im)
+{
+	if (im->prev)
+		im->prev->next = im->next;
+	else
+		term.images = im->next;
+	if (im->next)
+		im->next->prev = im->prev;
+	if (im->pixmap)
+		XFreePixmap(xw.dpy, (Drawable)im->pixmap);
+	free(im->pixels);
+	free(im);
+}
+
+void
 draw(void)
 {
+	ImageList *im;
+	int x, y;
+	int n = 0;
+	int nlimit = 256;
+	XRectangle *rects = NULL;
+	XGCValues gcvalues;
+	GC gc;
+
 	drawregion(0, 0, term.col, term.row);
+	for (im = term.images; im; im = im->next) {
+		if (im->should_delete) {
+			delete_image(im);
+			continue;
+		}
+		if (!im->pixmap) {
+			im->pixmap = (void *)XCreatePixmap(xw.dpy, xw.win, im->width, im->height, DefaultDepth(xw.dpy, xw.scr));
+			XImage ximage = {
+				.format = ZPixmap,
+				.data = (char *)im->pixels,
+				.width = im->width,
+				.height = im->height,
+				.xoffset = 0,
+				.byte_order = LSBFirst,
+				.bitmap_bit_order = MSBFirst,
+				.bits_per_pixel = 32,
+				.bytes_per_line = im->width * 4,
+				.bitmap_unit = 32,
+				.bitmap_pad = 32,
+				.depth = 24
+			};
+			XPutImage(xw.dpy, (Drawable)im->pixmap, dc.gc, &ximage, 0, 0, 0, 0, im->width, im->height);
+			free(im->pixels);
+			im->pixels = NULL;
+		}
+		n = 0;
+		memset(&gcvalues, 0, sizeof(gcvalues));
+		gc = XCreateGC(xw.dpy, xw.win, 0, &gcvalues);
+		for (y = im->y; y < im->y + (im->height+win.ch-1)/win.ch; y++) {
+			if (y >= 0 && y < term.row) {
+				for (x = im->x; x < im->x + (im->width+win.cw-1)/win.cw; x++) {
+					if (!rects)
+						rects = xmalloc(sizeof(XRectangle) * nlimit);
+					if (term.line[y][x].mode & ATTR_SIXEL) {
+						if (n > 0 && rects[n-1].x+rects[n-1].width == borderpx+x*win.cw && rects[n-1].y == borderpx+y*win.ch) {
+							rects[n-1].width += win.cw;
+						} else {
+							rects[n].x = borderpx+x*win.cw;
+							rects[n].y = borderpx+y*win.ch;
+							rects[n].width = win.cw;
+							rects[n].height = win.ch;
+							if (++n == nlimit && (rects = realloc(rects, sizeof(XRectangle) * (nlimit *= 2))) == NULL)
+								die("Out of memory\n");
+						}
+					}
+				}
+			}
+			if (n > 1 && rects[n-2].x == rects[n-1].x && rects[n-2].width == rects[n-1].width) {
+				if (rects[n-2].y+rects[n-2].height == rects[n-1].y) {
+					rects[n-2].height += win.ch;
+					n--;
+				}
+			}
+		}
+		if (n == 0) {
+			delete_image(im);
+			continue;
+		}
+		if (n > 1)
+			XSetClipRectangles(xw.dpy, gc, 0, 0, rects, n, YXSorted);
+		XCopyArea(xw.dpy, (Drawable)im->pixmap, xw.buf, gc, 0, 0, im->width, im->height, borderpx + im->x * win.cw, borderpx + im->y * win.ch);
+		XFreeGC(xw.dpy, gc);
+	}
 	XCopyArea(xw.dpy, xw.buf, xw.win, dc.gc, 0, 0, win.w,
 			win.h, 0, 0);
 	XSetForeground(xw.dpy, dc.gc,
 			dc.col[IS_SET(MODE_REVERSE)?
 				defaultfg : defaultbg].pixel);
+	free(rects);
 }
 
 void