diff --git a/CHANGELOG.md b/CHANGELOG.md
index d1d9629e..2832979e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -82,6 +82,7 @@
   (https://codeberg.org/dnkl/foot/issues/376).
 * The minimum version requirement for the libxkbcommon dependency is
   now 1.0.0.
+* Empty pixel rows at the bottom of a sixel is now trimmed.
 
 
 ### Deprecated
diff --git a/scripts/generate-alt-random-writes.py b/scripts/generate-alt-random-writes.py
index 2e51082b..2a3b23a5 100755
--- a/scripts/generate-alt-random-writes.py
+++ b/scripts/generate-alt-random-writes.py
@@ -158,20 +158,37 @@ def main():
             reset_actions = ['\033[m', '\033[39m', '\033[49m']
             out.write(random.choice(reset_actions))
 
-    # Leave alt screen
-    out.write('\033[m\033[r\033[?1049l')
+    # Reset colors
+    out.write('\033[m\033[r')
 
     if opts.sixel:
         # The sixel 'alphabet'
         sixels = '?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~'
 
-        for _ in range(200):
-            # Offset image
-            out.write(' ' * (random.randrange(cols // 2)))
+        last_pos = None
+        last_size = None
+
+        for _ in range(100):
+            if last_pos is not None and random.randrange(2):
+                # Overwrite last sixel. I.e. use same position and
+                # size as last sixel
+                pass
+            else:
+                # Random origin in upper left quadrant
+                last_pos = random.randrange(lines // 2) + 1, random.randrange(cols // 2) + 1
+                last_size = random.randrange(height // 2), random.randrange(width // 2)
+
+            out.write(f'\033[{last_pos[0]};{last_pos[1]}H')
+            six_height, six_width = last_size
+            six_rows = (six_height + 5) // 6  # Round up; each sixel is 6 pixels
 
             # Begin sixel
             out.write('\033Pq')
 
+            # Sixel size. Without this, sixels will be
+            # auto-resized on cell-boundaries.
+            out.write(f'"1;1;{six_width};{six_height}')
+
             # Set up 256 random colors
             for idx in range(256):
                 # param 2: 1=HLS, 2=RGB.
@@ -179,29 +196,36 @@ def main():
                 #              (except 'hue' which is 0..360)
                 out.write(f'#{idx};2;{random.randrange(101)};{random.randrange(101)};{random.randrange(101)}')
 
-            # Randomize image width/height
-            six_height = random.randrange(height // 2)
-            six_width = random.randrange(width // 2)
+            for row in range(six_rows):
+                band_count = random.randrange(4, 33)
+                for band in range(band_count):
+                    # Choose a random color
+                    out.write(f'#{random.randrange(256)}')
 
-            # Sixel size. Without this, sixels will be
-            # auto-resized on cell-boundaries. We expect programs
-            # to emit this sequence since otherwise you cannot get
-            # correctly sized images.
-            out.write(f'"0;0;{six_width};{six_height}')
+                    if random.randrange(2):
+                        for col in range(six_width):
+                            out.write(f'{random.choice(sixels)}')
+                    else:
+                        pix_left = six_width
+                        while pix_left > 0:
+                            repeat_count = random.randrange(1, pix_left + 1)
+                            out.write(f'!{repeat_count}{random.choice(sixels)}')
+                            pix_left -= repeat_count
 
-            for row in range(six_height // 6):  # Each sixel is 6 pixels
-                # Choose a random color
-                out.write(f'#{random.randrange(256)}')
-
-                for col in range(six_width):
-                    out.write(f'{random.choice(sixels)}')
-
-                # Next line
-                out.write('-')
+                    # Next line
+                    if band + 1 < band_count:
+                        # Move cursor to beginning of current row
+                        out.write('$')
+                    elif row + 1 < six_rows:
+                        # Newline
+                        out.write('-')
 
             # End sixel
             out.write('\033\\')
 
+    # Leave alt screen
+    out.write('\033[?1049l')
+
 
 if __name__ == '__main__':
     sys.exit(main())
diff --git a/sixel.c b/sixel.c
index 6d57b6c4..776750a2 100644
--- a/sixel.c
+++ b/sixel.c
@@ -37,8 +37,9 @@ sixel_init(struct terminal *term)
 
     term->sixel.state = SIXEL_DECSIXEL;
     term->sixel.pos = (struct coord){0, 0};
+    term->sixel.max_non_empty_row_no = 0;
+    term->sixel.row_byte_ofs = 0;
     term->sixel.color_idx = 0;
-    term->sixel.max_col = 0;
     term->sixel.param = 0;
     term->sixel.param_idx = 0;
     memset(term->sixel.params, 0, sizeof(term->sixel.params));
@@ -695,6 +696,13 @@ sixel_reflow(struct terminal *term)
 void
 sixel_unhook(struct terminal *term)
 {
+    if (term->sixel.image.height > term->sixel.max_non_empty_row_no + 1) {
+        LOG_DBG(
+            "last row only partially filled, reducing image height: %d -> %d",
+            term->sixel.image.height, term->sixel.max_non_empty_row_no + 1);
+        term->sixel.image.height = term->sixel.max_non_empty_row_no + 1;
+    }
+
     int pixel_row_idx = 0;
     int pixel_rows_left = term->sixel.image.height;
     const int stride = term->sixel.image.width * sizeof(uint32_t);
@@ -825,7 +833,6 @@ sixel_unhook(struct terminal *term)
     term->sixel.image.data = NULL;
     term->sixel.image.width = 0;
     term->sixel.image.height = 0;
-    term->sixel.max_col = 0;
     term->sixel.pos = (struct coord){0, 0};
 
     free(term->sixel.private_palette);
@@ -837,6 +844,88 @@ sixel_unhook(struct terminal *term)
     render_refresh(term);
 }
 
+static bool
+resize_horizontally(struct terminal *term, int new_width)
+{
+    LOG_DBG("resizing image horizontally: %dx(%d) -> %dx(%d)",
+            term->sixel.image.width, term->sixel.image.height,
+            new_width, term->sixel.image.height);
+
+    if (unlikely(new_width > term->sixel.max_width)) {
+        LOG_WARN("maximum image dimensions reached");
+        return false;
+    }
+
+    uint32_t *old_data = term->sixel.image.data;
+    const int old_width = term->sixel.image.width;
+    const int height = term->sixel.image.height;
+
+    int alloc_height = (height + 6 - 1) / 6 * 6;
+
+    xassert(new_width > 0);
+    xassert(alloc_height > 0);
+
+    /* Width (and thus stride) change - need to allocate a new buffer */
+    uint32_t *new_data = xmalloc(new_width * alloc_height * sizeof(uint32_t));
+
+    /* Copy old rows, and initialize new columns to background color */
+    for (int r = 0; r < height; r++) {
+        memcpy(&new_data[r * new_width],
+               &old_data[r * old_width],
+               old_width * sizeof(uint32_t));
+
+        for (int c = old_width; c < new_width; c++)
+            new_data[r * new_width + c] = color_with_alpha(term, term->colors.bg);
+    }
+
+    free(old_data);
+
+    term->sixel.image.data = new_data;
+    term->sixel.image.width = new_width;
+    term->sixel.row_byte_ofs = term->sixel.pos.row * new_width;
+    return true;
+}
+
+static bool
+resize_vertically(struct terminal *term, int new_height)
+{
+    LOG_DBG("resizing image vertically: (%d)x%d -> (%d)x%d",
+            term->sixel.image.width, term->sixel.image.height,
+            term->sixel.image.width, new_height);
+
+    if (unlikely(new_height > term->sixel.max_height)) {
+        LOG_WARN("maximum image dimensions reached");
+        return false;
+    }
+
+    uint32_t *old_data = term->sixel.image.data;
+    const int width = term->sixel.image.width;
+    const int old_height = term->sixel.image.height;
+
+    int alloc_height = (new_height + 6 - 1) / 6 * 6;
+
+    xassert(width > 0);
+    xassert(new_height > 0);
+
+    uint32_t *new_data = realloc(
+        old_data, width * alloc_height * sizeof(uint32_t));
+
+    if (new_data == NULL) {
+        LOG_ERRNO("failed to reallocate sixel image buffer");
+        return false;
+    }
+
+    /* Initialize new rows to background color */
+    for (int r = old_height; r < new_height; r++) {
+        for (int c = 0; c < width; c++)
+            new_data[r * width + c] = color_with_alpha(term, term->colors.bg);
+    }
+
+    term->sixel.image.data = new_data;
+    term->sixel.image.height = new_height;
+    return true;
+}
+
 static bool
 resize(struct terminal *term, int new_width, int new_height)
 {
@@ -844,6 +933,13 @@ resize(struct terminal *term, int new_width, int new_height)
             term->sixel.image.width, term->sixel.image.height,
             new_width, new_height);
 
+    if (new_width > term->sixel.max_width ||
+        new_height > term->sixel.max_height)
+    {
+        LOG_WARN("maximum image dimensions reached");
+        return false;
+    }
+
     uint32_t *old_data = term->sixel.image.data;
     const int old_width = term->sixel.image.width;
     const int old_height = term->sixel.image.height;
@@ -892,47 +988,55 @@ resize(struct terminal *term, int new_width, int new_height)
     term->sixel.image.data = new_data;
     term->sixel.image.width = new_width;
     term->sixel.image.height = new_height;
+    term->sixel.row_byte_ofs = term->sixel.pos.row * new_width;
 
     return true;
 }
 
 static void
-sixel_add(struct terminal *term, uint32_t color, uint8_t sixel)
+sixel_add(struct terminal *term, int col, int width, uint32_t color, uint8_t sixel)
 {
-    //LOG_DBG("adding sixel %02hhx using color 0x%06x", sixel, color);
+    xassert(term->sixel.pos.col < term->sixel.image.width);
+    xassert(term->sixel.pos.row < term->sixel.image.height);
 
-    if (term->sixel.pos.col >= term->sixel.max_width ||
-        term->sixel.pos.row * 6 + 5 >= term->sixel.max_height)
-    {
-        return;
-    }
+    size_t ofs = term->sixel.row_byte_ofs + col;
+    uint32_t *data = &term->sixel.image.data[ofs];
 
-    if (term->sixel.pos.col >= term->sixel.image.width ||
-        term->sixel.pos.row * 6 + 5 >= (term->sixel.image.height + 6 - 1) / 6 * 6)
-    {
-        int width = max(
-            term->sixel.image.width,
-            max(term->sixel.max_col, term->sixel.pos.col + 1));
+    int max_non_empty_row = 0;
+    int row = term->sixel.pos.row;
 
-        int height = max(
-            term->sixel.image.height,
-            (term->sixel.pos.row + 1) * 6);
-
-        if (!resize(term, width, height))
-            return;
-    }
-
-    for (int i = 0; i < 6; i++, sixel >>= 1) {
+    for (int i = 0; i < 6; i++, sixel >>= 1, data += width) {
         if (sixel & 1) {
-            size_t pixel_row = term->sixel.pos.row * 6 + i;
-            size_t stride = term->sixel.image.width;
-            size_t idx = pixel_row * stride + term->sixel.pos.col;
-            term->sixel.image.data[idx] = color_with_alpha(term, color);
+            *data = color;
+            max_non_empty_row = row + i;
         }
     }
 
     xassert(sixel == 0);
-    term->sixel.pos.col++;
+
+    term->sixel.max_non_empty_row_no = max(
+        term->sixel.max_non_empty_row_no,
+        max_non_empty_row);
+}
+
+static void
+sixel_add_many(struct terminal *term, uint8_t c, unsigned count)
+{
+    uint32_t color = term->sixel.palette[term->sixel.color_idx];
+
+    int col = term->sixel.pos.col;
+    int width = term->sixel.image.width;
+
+    if (unlikely(col + count - 1 >= width)) {
+        width = col + count;
+        if (unlikely(!resize_horizontally(term, width)))
+            return;
+    }
+
+    for (unsigned i = 0; i < count; i++, col++)
+        sixel_add(term, col, width, color, c);
+
+    term->sixel.pos.col = col;
 }
 
 static void
@@ -959,16 +1063,26 @@ decsixel(struct terminal *term, uint8_t c)
         break;
 
     case '$':
-        if (term->sixel.pos.col > term->sixel.max_col)
-            term->sixel.max_col = term->sixel.pos.col;
-        term->sixel.pos.col = 0;
+        if (likely(term->sixel.pos.col <= term->sixel.max_width)) {
+            /*
+             * We set, and keep, ‘col’ outside the image boundary when
+             * we’ve reached the maximum image height, to avoid also
+             * having to check the row vs image height in the common
+             * path in sixel_add().
+             */
+            term->sixel.pos.col = 0;
+        }
         break;
 
     case '-':
-        if (term->sixel.pos.col > term->sixel.max_col)
-            term->sixel.max_col = term->sixel.pos.col;
-        term->sixel.pos.row++;
+        term->sixel.pos.row += 6;
         term->sixel.pos.col = 0;
+        term->sixel.row_byte_ofs += term->sixel.image.width * 6;
+
+        if (term->sixel.pos.row >= term->sixel.image.height) {
+            if (!resize_vertically(term, term->sixel.pos.row + 6))
+                term->sixel.pos.col = term->sixel.max_width + 1;
+        }
         break;
 
     case '?': case '@': case 'A': case 'B': case 'C': case 'D': case 'E':
@@ -981,7 +1095,7 @@ decsixel(struct terminal *term, uint8_t c)
     case 'p': case 'q': case 'r': case 's': case 't': case 'u': case 'v':
     case 'w': case 'x': case 'y': case 'z': case '{': case '|': case '}':
     case '~':
-        sixel_add(term, term->sixel.palette[term->sixel.color_idx], c - 63);
+        sixel_add_many(term, c - 63, 1);
         break;
 
     case ' ':
@@ -1031,6 +1145,7 @@ decgra(struct terminal *term, uint8_t c)
             ph <= term->sixel.max_height && pv <= term->sixel.max_width)
         {
             resize(term, ph, pv);
+            term->sixel.max_non_empty_row_no = pv - 1;
         }
 
         term->sixel.state = SIXEL_DECSIXEL;
@@ -1050,13 +1165,23 @@ decgri(struct terminal *term, uint8_t c)
         term->sixel.param += c - '0';
         break;
 
-    default:
-        //LOG_DBG("repeating '%c' %u times", c, term->sixel.param);
-        for (unsigned i = 0; i < term->sixel.param; i++)
-            decsixel(term, c);
+    case '?': case '@': case 'A': case 'B': case 'C': case 'D': case 'E':
+    case 'F': case 'G': case 'H': case 'I': case 'J': case 'K': case 'L':
+    case 'M': case 'N': case 'O': case 'P': case 'Q': case 'R': case 'S':
+    case 'T': case 'U': case 'V': case 'W': case 'X': case 'Y': case 'Z':
+    case '[': case '\\': case ']': case '^': case '_': case '`': case 'a':
+    case 'b': case 'c': case 'd': case 'e': case 'f': case 'g': case 'h':
+    case 'i': case 'j': case 'k': case 'l': case 'm': case 'n': case 'o':
+    case 'p': case 'q': case 'r': case 's': case 't': case 'u': case 'v':
+    case 'w': case 'x': case 'y': case 'z': case '{': case '|': case '}':
+    case '~': {
+        unsigned count = term->sixel.param;
+        if (likely(count > 0))
+            sixel_add_many(term, c - 63, count);
         term->sixel.state = SIXEL_DECSIXEL;
         break;
     }
+    }
 }
 
 static void
@@ -1114,7 +1239,8 @@ decgci(struct terminal *term, uint8_t c)
                 LOG_DBG("setting palette #%d = HLS %hhu/%hhu/%hhu (0x%06x)",
                         term->sixel.color_idx, hue, lum, sat, rgb);
 
-                term->sixel.palette[term->sixel.color_idx] = rgb;
+                term->sixel.palette[term->sixel.color_idx] =
+                    color_with_alpha(term, rgb);
                 break;
             }
 
@@ -1126,7 +1252,8 @@ decgci(struct terminal *term, uint8_t c)
                 LOG_DBG("setting palette #%d = RGB %hhu/%hhu/%hhu",
                         term->sixel.color_idx, r, g, b);
 
-                term->sixel.palette[term->sixel.color_idx] = r << 16 | g << 8 | b;
+                term->sixel.palette[term->sixel.color_idx] =
+                    color_with_alpha(term, r << 16 | g << 8 | b);
                 break;
             }
             }
diff --git a/terminal.h b/terminal.h
index e4e662fb..8be5dd74 100644
--- a/terminal.h
+++ b/terminal.h
@@ -521,8 +521,9 @@ struct terminal {
         } state;
 
         struct coord pos;    /* Current sixel coordinate */
+        int max_non_empty_row_no;
+        size_t row_byte_ofs; /* Byte position into image, for current row */
         int color_idx;       /* Current palette index */
-        int max_col;         /* Largest column index we've seen (aka the image width) */
         uint32_t *private_palette;   /* Private palette, used when private mode 1070 is enabled */
         uint32_t *shared_palette;    /* Shared palette, used when private mode 1070 is disabled */
         uint32_t *palette;   /* Points to either private_palette or shared_palette */