diff --git a/image-sixel.c b/image-sixel.c
index e2ab71307..fd25c6e37 100644
--- a/image-sixel.c
+++ b/image-sixel.c
@@ -485,7 +485,13 @@ sixel_to_image(struct sixel_image *si)
 		}
 	}
 	sixel_size_in_cells(si, &sx, &sy);
-	im = image_create(si->x, si->y, sx, sy, pixels);
+	if ((uint64_t)sx * si->xpixel > UINT_MAX ||
+	    (uint64_t)sy * si->ypixel > UINT_MAX) {
+		free(pixels);
+		return (NULL);
+	}
+	im = image_create(si->x, si->y, sx * si->xpixel, sy * si->ypixel,
+	    sx, sy, pixels);
 	if (im == NULL)
 		free(pixels);
 	return (im);
@@ -743,12 +749,29 @@ sixel_from_image(struct image *im, u_int ox, u_int oy, u_int cells_x,
 	u_int			 x, y, sx, sy, sourcex, sourcey;
 	u_int			 sourcex0, sourcey0, sourcewidth, sourceheight;
 	u_int			 r, g, b, colour, i;
+	uint64_t		 destination_width, destination_height;
+	uint64_t		 content_width, content_height, x0, x1, y0, y1;
 
-	if ((uint64_t)cells_x * xpixel > UINT_MAX ||
-	    (uint64_t)cells_y * ypixel > UINT_MAX)
+	destination_width = (uint64_t)im->sx * xpixel;
+	destination_height = (uint64_t)im->sy * ypixel;
+	if (destination_width > UINT_MAX || destination_height > UINT_MAX)
 		return (NULL);
-	sx = cells_x * xpixel;
-	sy = cells_y * ypixel;
+	content_width = ((uint64_t)im->width * destination_width +
+	    im->canvas_width - 1) / im->canvas_width;
+	content_height = ((uint64_t)im->height * destination_height +
+	    im->canvas_height - 1) / im->canvas_height;
+	x0 = (uint64_t)ox * xpixel;
+	y0 = (uint64_t)oy * ypixel;
+	x1 = ((uint64_t)ox + cells_x) * xpixel;
+	y1 = ((uint64_t)oy + cells_y) * ypixel;
+	if (x1 > content_width)
+		x1 = content_width;
+	if (y1 > content_height)
+		y1 = content_height;
+	if (x1 <= x0 || y1 <= y0)
+		return (NULL);
+	sx = x1 - x0;
+	sy = y1 - y0;
 	if (sx == 0 || sy == 0 || sx > SIXEL_WIDTH_LIMIT ||
 	    sy > SIXEL_HEIGHT_LIMIT)
 		return (NULL);
diff --git a/image.c b/image.c
index eb82a265f..104377b04 100644
--- a/image.c
+++ b/image.c
@@ -132,14 +132,19 @@ image_sample(struct image *im, uint64_t sample_x, uint64_t sample_y,
 	uint64_t	 brightness = 0, count = 0;
 	u_int		 x, y, x0, x1, y0, y1;
 
-	x0 = sample_x * im->width / sample_columns;
-	x1 = (sample_x + 1) * im->width / sample_columns;
-	y0 = sample_y * im->height / sample_rows;
-	y1 = (sample_y + 1) * im->height / sample_rows;
+	x0 = sample_x * im->canvas_width / sample_columns;
+	x1 = ((sample_x + 1) * im->canvas_width + sample_columns - 1) /
+	    sample_columns;
+	y0 = sample_y * im->canvas_height / sample_rows;
+	y1 = ((sample_y + 1) * im->canvas_height + sample_rows - 1) /
+	    sample_rows;
 	if (x1 <= x0)
 		x1 = x0 + 1;
 	if (y1 <= y0)
 		y1 = y0 + 1;
+	count = (uint64_t)(x1 - x0) * (y1 - y0);
+	if (x0 >= im->width || y0 >= im->height)
+		return;
 	if (x1 > im->width)
 		x1 = im->width;
 	if (y1 > im->height)
@@ -155,7 +160,6 @@ image_sample(struct image *im, uint64_t sample_x, uint64_t sample_y,
 			brightness += ((2126ULL * pixel[0] +
 			    7152ULL * pixel[1] + 722ULL * pixel[2]) / 10000) *
 			    pixel[3] / 255;
-			count++;
 		}
 	}
 	if (count == 0)
@@ -206,11 +210,13 @@ image_find(u_int id)
 }
 
 struct image *
-image_create(u_int width, u_int height, u_int sx, u_int sy, u_char *pixels)
+image_create(u_int width, u_int height, u_int canvas_width,
+    u_int canvas_height, u_int sx, u_int sy, u_char *pixels)
 {
 	struct image	*im;
 
-	if (width == 0 || height == 0 || sx == 0 || sy == 0 || pixels == NULL)
+	if (width == 0 || height == 0 || canvas_width < width ||
+	    canvas_height < height || sx == 0 || sy == 0 || pixels == NULL)
 		return (NULL);
 	if ((uint64_t)width * height * 4 > SIZE_MAX)
 		return (NULL);
@@ -227,6 +233,8 @@ image_create(u_int width, u_int height, u_int sx, u_int sy, u_char *pixels)
 	im->references = 1;
 	im->width = width;
 	im->height = height;
+	im->canvas_width = canvas_width;
+	im->canvas_height = canvas_height;
 	im->sx = sx;
 	im->sy = sy;
 	im->stride = (size_t)width * 4;
@@ -234,8 +242,9 @@ image_create(u_int width, u_int height, u_int sx, u_int sy, u_char *pixels)
 	im->pixels = pixels;
 
 	RB_INSERT(images, &images, im);
-	log_debug("%s: image %u is %ux%u pixels, %ux%u cells", __func__,
-	    im->id, width, height, sx, sy);
+	log_debug("%s: image %u is %ux%u pixels on %ux%u canvas, "
+	    "%ux%u cells", __func__, im->id, width, height, canvas_width,
+	    canvas_height, sx, sy);
 	return (im);
 }
 
@@ -305,14 +314,16 @@ image_get_pixel_rectangle(const struct image *im, u_int x, u_int y,
 	if (height > im->sy - y)
 		height = im->sy - y;
 
-	*px = (uint64_t)x * im->width / im->sx;
-	*py = (uint64_t)y * im->height / im->sy;
-	x1 = (uint64_t)(x + width) * im->width / im->sx;
-	y1 = (uint64_t)(y + height) * im->height / im->sy;
-	if (*px >= im->width)
-		*px = im->width - 1;
-	if (*py >= im->height)
-		*py = im->height - 1;
+	*px = (uint64_t)x * im->canvas_width / im->sx;
+	*py = (uint64_t)y * im->canvas_height / im->sy;
+	x1 = ((uint64_t)(x + width) * im->canvas_width + im->sx - 1) /
+	    im->sx;
+	y1 = ((uint64_t)(y + height) * im->canvas_height + im->sy - 1) /
+	    im->sy;
+	if (*px >= im->width || *py >= im->height) {
+		*px = *py = 0;
+		return;
+	}
 	if (x1 <= *px)
 		x1 = *px + 1;
 	if (y1 <= *py)
diff --git a/regress/image-support.sh b/regress/image-support.sh
index 82564ca4d..05eabc128 100755
--- a/regress/image-support.sh
+++ b/regress/image-support.sh
@@ -69,10 +69,12 @@ $TMUX copy-mode -t:4 || exit 1
 $TMUX send-keys -t:4 -X history-top || exit 1
 $TMUX capture-pane -pt:4 >$TMP || exit 1
 
-# A client without an image feature gets the brightness-based ASCII backend.
+# A 26-pixel raster occupies two default 16-pixel cells, but the final cell
+# remains only partially filled instead of stretching the raster to 32 pixels.
+# A client without an image feature exposes this in the sampled text backend.
 $TMUX kill-server 2>/dev/null
 $TMUX2 new-session -d -x 10 -y 4 "
-	printf '\033_Ga=T,q=2,f=32,s=2,v=2,c=2,r=2;/wAA/wD/AP8AAP///////w==\033\\'
+	printf '\033Pq\"1;1;26;26#0;2;100;100;100#0!26~-!26~-!26~-!26~-!26B\033\\'
 	sleep 10" || exit 1
 $TMUX2 set -g status off || exit 1
 $TMUX new-session -d -x 10 -y 4 || exit 1
@@ -80,9 +82,8 @@ $TMUX set -g status off || exit 1
 $TMUX send-keys -l "$TMUX2 attach-session" || exit 1
 $TMUX send-keys Enter || exit 1
 sleep 1
-$TMUX capture-pane -pS0 -E1 >$TMP || exit 1
-[ "$(sed -n 1p $TMP)" = ".*" ] || exit 1
-[ "$(sed -n 2p $TMP)" = " @" ] || exit 1
+$TMUX capture-pane -pS0 -E0 >$TMP || exit 1
+grep -q '^#=' $TMP || exit 1
 
 # A selection redraw uses the single-cell path. It must leave ASCII image
 # cells visible (graphical clients skip these cells to avoid erasing pixels).
@@ -92,8 +93,7 @@ $TMUX2 send-keys -X start-of-line || exit 1
 $TMUX2 send-keys -X begin-selection || exit 1
 $TMUX2 send-keys -X cursor-right || exit 1
 sleep 1
-$TMUX capture-pane -pS0 -E1 >$TMP || exit 1
-sed -n 1p $TMP | grep -q '^\.\*' || exit 1
-sed -n 2p $TMP | grep -q '^ @' || exit 1
+$TMUX capture-pane -pS0 -E0 >$TMP || exit 1
+grep -q '^#=' $TMP || exit 1
 
 exit 0
diff --git a/tmux.h b/tmux.h
index c553b4feb..ca2b282f1 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1061,6 +1061,8 @@ struct image {
 	u_int			 references;
 	u_int			 width;
 	u_int			 height;
+	u_int			 canvas_width;
+	u_int			 canvas_height;
 	u_int			 sx;
 	u_int			 sy;
 	size_t			 stride;
@@ -4255,7 +4257,8 @@ char		*regsub(const char *, const char *, const char *, int);
 
 #ifdef ENABLE_IMAGES
 /* image.c */
-struct image	*image_create(u_int, u_int, u_int, u_int, u_char *);
+struct image	*image_create(u_int, u_int, u_int, u_int, u_int, u_int,
+		     u_char *);
 struct image	*image_find(u_int);
 void		 image_ref(u_int);
 void		 image_free(u_int);