Implementation of show_bitmap_1d()

micropython/modules/pico_scroll/README.md

@@ -85,6 +85,24 @@ image = bytearray(0 for j in range(width * height))
 picoscroll.set_pixels(image)
 ```
 
+### show_bitmap_1d
+
+Show a view of a bitmap stored as the 7 least significant bits of
+bytes in a `bytearray`, top-down. Individual pixels are set to
+`brightness` based on individual bit values, with the view defined by
+the offset and the width of the scroll (i.e. 17 columns). Changes will
+not be visible until `update()` is called.
+
+```python
+bitmap = bytearray(j for j in range 127)
+for offset in range(-17, 127):
+    picoscroll.show_bitmap_1d(bitmap, 16, offset)
+    picoscroll.update()
+```
+
+will scroll a binary counter across the display (i.e. show `0x00` to
+`0x7f` in binary).
+
 ### update
 
 Pushes pixel data from the Pico to the Scroll Pack.  Until this function is called any `set_pixel` or `clear` calls won't have any visible effect.

micropython/modules/pico_scroll/pico_scroll.c

@@ -21,6 +21,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_0(picoscroll_get_height_obj, picoscroll_get_heigh
 STATIC MP_DEFINE_CONST_FUN_OBJ_0(picoscroll_update_obj, picoscroll_update);
 STATIC MP_DEFINE_CONST_FUN_OBJ_3(picoscroll_set_pixel_obj, picoscroll_set_pixel);
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(picoscroll_set_pixels_obj, picoscroll_set_pixels);
+STATIC MP_DEFINE_CONST_FUN_OBJ_3(picoscroll_show_bitmap_1d_obj, picoscroll_show_bitmap_1d);
 STATIC MP_DEFINE_CONST_FUN_OBJ_0(picoscroll_clear_obj, picoscroll_clear);
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(picoscroll_is_pressed_obj, picoscroll_is_pressed);
 
@@ -33,6 +34,7 @@ STATIC const mp_map_elem_t picoscroll_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_update), MP_ROM_PTR(&picoscroll_update_obj) },
     { MP_ROM_QSTR(MP_QSTR_set_pixel), MP_ROM_PTR(&picoscroll_set_pixel_obj) },
     { MP_ROM_QSTR(MP_QSTR_set_pixels), MP_ROM_PTR(&picoscroll_set_pixels_obj) },
+    { MP_ROM_QSTR(MP_QSTR_show_bitmap_1d), MP_ROM_PTR(&picoscroll_show_bitmap_1d_obj) },
     { MP_ROM_QSTR(MP_QSTR_clear), MP_ROM_PTR(&picoscroll_clear_obj) },
     { MP_ROM_QSTR(MP_QSTR_is_pressed), MP_ROM_PTR(&picoscroll_is_pressed_obj) },        
     { MP_ROM_QSTR(MP_QSTR_BUTTON_A), MP_ROM_INT(BUTTON_A) },

micropython/modules/pico_scroll/pico_scroll.cpp

@@ -13,8 +13,8 @@ extern "C" {
 #include "pico_scroll.h"
 
 #define NOT_INITIALISED_MSG     "Cannot call this function, as picoscroll is not initialised. Call picoscroll.init() first."
-
 #define BUFFER_TOO_SMALL_MSG "bytearray too small: len(image) < width * height."
+#define INCORRECT_SIZE_MSG "Scroll height wrong: > 8 pixels."
 
 mp_obj_t picoscroll_init() {
     if(scroll == nullptr)
@@ -84,6 +84,47 @@ mp_obj_t picoscroll_set_pixels(mp_obj_t image_obj) {
     return mp_const_none;
 }
 
+mp_obj_t picoscroll_show_bitmap_1d(mp_obj_t bitmap_obj, mp_obj_t brightness_obj, mp_obj_t offset_obj) {
+    if(scroll != nullptr) {
+        mp_buffer_info_t bufinfo;
+	mp_get_buffer_raise(bitmap_obj, &bufinfo, MP_BUFFER_RW);
+        int offset = mp_obj_get_int(offset_obj);
+        int brightness = mp_obj_get_int(brightness_obj);
+	int length = bufinfo.len;
+	int width = PicoScroll::WIDTH;
+	int height = PicoScroll::HEIGHT;
+
+	// this obviously shouldn't happen as the scroll is 17x7 pixels
+	if (height > (int) sizeof(unsigned char)) {
+	    mp_raise_msg(&mp_type_RuntimeError, INCORRECT_SIZE_MSG);
+	}
+
+	unsigned char * values = (unsigned char *) bufinfo.buf;
+
+	// clear the scroll, so only need to write visible bytes
+	scroll->clear();
+
+	if ((offset < -width) || (offset > length)) {
+	    return mp_const_none;
+	}
+
+	for (int x = 0; x < width; x++) {
+	    int k = offset + x;
+	    if ((k >= 0) && (k <= length)) {
+	        unsigned char col = values[k];
+		for (int y = 0; y < height; y++) {
+		    int val = brightness * ((col >> y) & 1);
+		    scroll->set_pixel(x, height - 1 - y, val);
+		}
+	    }
+	}
+    } else {
+        mp_raise_msg(&mp_type_RuntimeError, NOT_INITIALISED_MSG);
+    }
+
+    return mp_const_none;
+}
+
 mp_obj_t picoscroll_clear() {
     if(scroll != nullptr)
         scroll->clear();

micropython/modules/pico_scroll/pico_scroll.h

@@ -8,5 +8,6 @@ extern mp_obj_t picoscroll_get_height();
 extern mp_obj_t picoscroll_update();
 extern mp_obj_t picoscroll_set_pixel(mp_obj_t x_obj, mp_obj_t y_obj, mp_obj_t v_obj);
 extern mp_obj_t picoscroll_set_pixels(mp_obj_t image_obj);
+extern mp_obj_t picoscroll_show_bitmap_1d(mp_obj_t bitmap_obj, mp_obj_t brightness, mp_obj_t offset);
 extern mp_obj_t picoscroll_clear();
 extern mp_obj_t picoscroll_is_pressed(mp_obj_t button_obj);