diff --git a/shared-module/displayio/Bitmap.c b/shared-module/displayio/Bitmap.c
index c9ea834285..1831ac697d 100644
--- a/shared-module/displayio/Bitmap.c
+++ b/shared-module/displayio/Bitmap.c
@@ -105,17 +105,92 @@ uint32_t common_hal_displayio_bitmap_get_pixel(displayio_bitmap_t *self, int16_t
     return 0;
 }
 
+void displayio_bitmap_set_dirty_area(displayio_bitmap_t *self, int16_t x1, int16_t y1, int16_t x2, int16_t y2) {
+    // Update the bitmap's dirty region with the rectangle bounded by (x1,y1) and (x2, y2)
+
+    // Arrange x1 < x2, y1 < y2
+    if (x1 > x2) {
+        int16_t temp = x1;
+        x1 = x2;
+        x2 = temp;
+    }
+    if (y1 > y2) {
+        int16_t temp = y1;
+        y1 = y2;
+        y2 = temp;
+    }
+
+    // Update the dirty area.
+    if (self->dirty_area.x1 == self->dirty_area.x2) {
+        self->dirty_area.x1 = x1;
+        self->dirty_area.x2 = x2;
+        self->dirty_area.y1 = y1;
+        self->dirty_area.y2 = y2;
+    } else {
+        if (x1 < self->dirty_area.x1) {
+            self->dirty_area.x1 = x1;
+        }
+        if (x2 > self->dirty_area.x2) {
+            self->dirty_area.x2 = x2;
+        }
+        if (y1 < self->dirty_area.y1) {
+            self->dirty_area.y1 = y1;
+        }
+        if (y2 > self->dirty_area.y2) {
+            self->dirty_area.y2 = y2;
+        }
+    }
+}
+
+void displayio_bitmap_write_pixel(displayio_bitmap_t *self, int16_t x, int16_t y, uint32_t value) {
+    // Writes the color index value into a pixel position
+    // Must update the dirty area separately
+
+    // Update one pixel of data
+    int32_t row_start = y * self->stride;
+    uint32_t bytes_per_value = self->bits_per_value / 8;
+    if (bytes_per_value < 1) {
+        uint32_t bit_position = (sizeof(size_t) * 8 - ((x & self->x_mask) + 1) * self->bits_per_value);
+        uint32_t index = row_start + (x >> self->x_shift);
+        uint32_t word = self->data[index];
+        word &= ~(self->bitmask << bit_position);
+        word |= (value & self->bitmask) << bit_position;
+        self->data[index] = word;
+    } else {
+        size_t* row = self->data + row_start;
+        if (bytes_per_value == 1) {
+            ((uint8_t*) row)[x] = value;
+        } else if (bytes_per_value == 2) {
+            ((uint16_t*) row)[x] = value;
+        } else if (bytes_per_value == 4) {
+            ((uint32_t*) row)[x] = value;
+        }
+    }
+}
+
 void common_hal_displayio_bitmap_blit(displayio_bitmap_t *self, int16_t x, int16_t y, displayio_bitmap_t *source,
                             int16_t x1, int16_t y1, int16_t x2, int16_t y2, uint32_t skip_index, bool skip_index_none) {
-    // Copy complete "source" bitmap into "self" bitmap at location x,y in the "self"
-    // Add a boolean to determine if all values are copied, or only if non-zero
+    // Copy region of "source" bitmap into "self" bitmap at location x,y in the "self"
     // If skip_value is encountered in the source bitmap, it will not be copied.
     // If skip_value is `None`, then all pixels are copied.
+    // This function assumes input checks were performed for pixel index entries.
 
     if (self->read_only) {
         mp_raise_RuntimeError(translate("Read-only object"));
     }
 
+    // Update the dirty area
+    int16_t dirty_x_max = (x + (x2-x1));
+    if (dirty_x_max > self->width) {
+        dirty_x_max = self->width;
+    }
+    int16_t dirty_y_max = y + (y2-y1);
+    if (dirty_y_max > self->height) {
+        dirty_y_max = self->height;
+    }
+
+    displayio_bitmap_set_dirty_area(self, x, y, dirty_x_max, dirty_y_max);
+
     bool x_reverse = false;
     bool y_reverse = false;
 
@@ -142,7 +217,7 @@ void common_hal_displayio_bitmap_blit(displayio_bitmap_t *self, int16_t x, int16
                 if ((yd_index >= 0) && (yd_index < self->height) ) {
                     uint32_t value = common_hal_displayio_bitmap_get_pixel(source, xs_index, ys_index);
                     if ( (skip_index_none) || (value != skip_index) ) { // write if skip_value_none is True
-                            common_hal_displayio_bitmap_set_pixel(self, xd_index, yd_index, value);
+                            displayio_bitmap_write_pixel(self, xd_index, yd_index, value);
                     }
                 }
             }
@@ -154,45 +229,13 @@ void common_hal_displayio_bitmap_set_pixel(displayio_bitmap_t *self, int16_t x,
     if (self->read_only) {
         mp_raise_RuntimeError(translate("Read-only object"));
     }
-    // Update the dirty area.
-    if (self->dirty_area.x1 == self->dirty_area.x2) {
-        self->dirty_area.x1 = x;
-        self->dirty_area.x2 = x + 1;
-        self->dirty_area.y1 = y;
-        self->dirty_area.y2 = y + 1;
-    } else {
-        if (x < self->dirty_area.x1) {
-            self->dirty_area.x1 = x;
-        } else if (x >= self->dirty_area.x2) {
-            self->dirty_area.x2 = x + 1;
-        }
-        if (y < self->dirty_area.y1) {
-            self->dirty_area.y1 = y;
-        } else if (y >= self->dirty_area.y2) {
-            self->dirty_area.y2 = y + 1;
-        }
-    }
 
-    // Update our data
-    int32_t row_start = y * self->stride;
-    uint32_t bytes_per_value = self->bits_per_value / 8;
-    if (bytes_per_value < 1) {
-        uint32_t bit_position = (sizeof(size_t) * 8 - ((x & self->x_mask) + 1) * self->bits_per_value);
-        uint32_t index = row_start + (x >> self->x_shift);
-        uint32_t word = self->data[index];
-        word &= ~(self->bitmask << bit_position);
-        word |= (value & self->bitmask) << bit_position;
-        self->data[index] = word;
-    } else {
-        size_t* row = self->data + row_start;
-        if (bytes_per_value == 1) {
-            ((uint8_t*) row)[x] = value;
-        } else if (bytes_per_value == 2) {
-            ((uint16_t*) row)[x] = value;
-        } else if (bytes_per_value == 4) {
-            ((uint32_t*) row)[x] = value;
-        }
-    }
+    // update the dirty region
+    displayio_bitmap_set_dirty_area(self, x, y, x+1, y+1);
+
+    // write the pixel
+    displayio_bitmap_write_pixel(self, x, y, value);
+
 }
 
 displayio_area_t* displayio_bitmap_get_refresh_areas(displayio_bitmap_t *self, displayio_area_t* tail) {