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jimmojimmo
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Endianness handling for RGB565 framebuf mode.
The current behavior uses the CPU endianness, which I found surprising: ``` b = bytearray(2) f = framebuf.FrameBuffer(b, 1, 1, framebuf.RGB565) f.fill(0xabcd) print(b) # bytearray(b'\xcd\xab') ``` I would expect that to result in `bytearray(b'\xab\xcd')`. The RGB565 OLED that I'm using needs the bytes arranged big-endian, so currently this means pushing the endianness-handling to the user of FrameBuffer. This commits retains the existing behavior for backwards-compatibility but adds two new modes `RGB565_BE` and `RGB565_LE` to allow the user to explicitly set the behavior. The existing `RGB565` will use whatever the CPU endianness is.
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4 files changed

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4 files changed

+133
-61
lines changed

‎docs/library/framebuf.rst

Lines changed: 12 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -146,7 +146,18 @@ Constants
146146

147147
.. data:: framebuf.RGB565
148148

149-
Red Green Blue (16-bit, 5+6+5) color format
149+
Red Green Blue (16-bit, 5+6+5) device-endian color format
150+
This will default to the device's native endianness (likely to be little-endian).
151+
152+
.. data:: framebuf.RGB565_BE
153+
154+
Red Green Blue (16-bit, 5+6+5) big-endian color format
155+
This will result in a pixel color value of `0xabcd` being stored in the buffer as `[0xab, 0xcd]`.
156+
157+
.. data:: framebuf.RGB565_LE
158+
159+
Red Green Blue (16-bit, 5+6+5) little-endian color format
160+
This will result in a pixel color value of `0xabcd` being stored in the buffer as `[0xcd, 0xab]`.
150161

151162
.. data:: framebuf.GS2_HMSB
152163

‎extmod/modframebuf.c

Lines changed: 43 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -27,6 +27,7 @@
2727
#include <stdio.h>
2828
#include <string.h>
2929

30+
#include "py/binary.h"
3031
#include "py/runtime.h"
3132

3233
#if MICROPY_PY_FRAMEBUF
@@ -52,13 +53,14 @@ typedef struct _mp_framebuf_p_t {
5253
} mp_framebuf_p_t;
5354

5455
// constants for formats
55-
#define FRAMEBUF_MVLSB (0)
56-
#define FRAMEBUF_RGB565 (1)
57-
#define FRAMEBUF_GS2_HMSB (5)
58-
#define FRAMEBUF_GS4_HMSB (2)
59-
#define FRAMEBUF_GS8 (6)
60-
#define FRAMEBUF_MHLSB (3)
61-
#define FRAMEBUF_MHMSB (4)
56+
#define FRAMEBUF_MVLSB (0)
57+
#define FRAMEBUF_RGB565_BE (1)
58+
#define FRAMEBUF_RGB565_LE (7)
59+
#define FRAMEBUF_GS2_HMSB (5)
60+
#define FRAMEBUF_GS4_HMSB (2)
61+
#define FRAMEBUF_GS8 (6)
62+
#define FRAMEBUF_MHLSB (3)
63+
#define FRAMEBUF_MHMSB (4)
6264

6365
// Functions for MHLSB and MHMSB
6466

@@ -114,16 +116,27 @@ STATIC void mvlsb_fill_rect(const mp_obj_framebuf_t *fb, int x, int y, int w, in
114116

115117
// Functions for RGB565 format
116118

119+
STATIC void rgb565_flip_endian(uint32_t* col, uint8_t format) {
120+
if ((MP_ENDIANNESS_LITTLE && format == FRAMEBUF_RGB565_BE) || (MP_ENDIANNESS_BIG && format == FRAMEBUF_RGB565_LE)) {
121+
*col = ((*col & 0xff) << 8) | ((*col >> 8) & 0xff);
122+
}
123+
}
124+
117125
STATIC void rgb565_setpixel(const mp_obj_framebuf_t *fb, int x, int y, uint32_t col) {
126+
rgb565_flip_endian(&col, fb->format);
118127
((uint16_t*)fb->buf)[x + y * fb->stride] = col;
119128
}
120129

121130
STATIC uint32_t rgb565_getpixel(const mp_obj_framebuf_t *fb, int x, int y) {
122-
return ((uint16_t*)fb->buf)[x + y * fb->stride];
131+
uint32_t col = ((uint16_t*)fb->buf)[x + y * fb->stride];
132+
rgb565_flip_endian(&col, fb->format);
133+
return col;
123134
}
124135

125136
STATIC void rgb565_fill_rect(const mp_obj_framebuf_t *fb, int x, int y, int w, int h, uint32_t col) {
137+
rgb565_flip_endian(&col, fb->format);
126138
uint16_t *b = &((uint16_t*)fb->buf)[x + y * fb->stride];
139+
127140
while (h--) {
128141
for (int ww = w; ww; --ww) {
129142
*b++ = col;
@@ -228,14 +241,25 @@ STATIC void gs8_fill_rect(const mp_obj_framebuf_t *fb, int x, int y, int w, int
228241

229242
STATIC mp_framebuf_p_t formats[] = {
230243
[FRAMEBUF_MVLSB] = {mvlsb_setpixel, mvlsb_getpixel, mvlsb_fill_rect},
231-
[FRAMEBUF_RGB565] = {rgb565_setpixel, rgb565_getpixel, rgb565_fill_rect},
244+
[FRAMEBUF_RGB565_BE] = {rgb565_setpixel, rgb565_getpixel, rgb565_fill_rect},
245+
[FRAMEBUF_RGB565_LE] = {rgb565_setpixel, rgb565_getpixel, rgb565_fill_rect},
232246
[FRAMEBUF_GS2_HMSB] = {gs2_hmsb_setpixel, gs2_hmsb_getpixel, gs2_hmsb_fill_rect},
233247
[FRAMEBUF_GS4_HMSB] = {gs4_hmsb_setpixel, gs4_hmsb_getpixel, gs4_hmsb_fill_rect},
234248
[FRAMEBUF_GS8] = {gs8_setpixel, gs8_getpixel, gs8_fill_rect},
235249
[FRAMEBUF_MHLSB] = {mono_horiz_setpixel, mono_horiz_getpixel, mono_horiz_fill_rect},
236250
[FRAMEBUF_MHMSB] = {mono_horiz_setpixel, mono_horiz_getpixel, mono_horiz_fill_rect},
237251
};
238252

253+
STATIC inline size_t bytes_per_pixel(const mp_obj_framebuf_t *fb) {
254+
switch (fb->format) {
255+
case FRAMEBUF_RGB565_BE:
256+
case FRAMEBUF_RGB565_LE:
257+
return 2;
258+
default:
259+
return 1;
260+
}
261+
}
262+
239263
static inline void setpixel(const mp_obj_framebuf_t *fb, int x, int y, uint32_t col) {
240264
formats[fb->format].setpixel(fb, x, y, col);
241265
}
@@ -281,7 +305,8 @@ STATIC mp_obj_t framebuf_make_new(const mp_obj_type_t *type, size_t n_args, size
281305

282306
switch (o->format) {
283307
case FRAMEBUF_MVLSB:
284-
case FRAMEBUF_RGB565:
308+
case FRAMEBUF_RGB565_BE:
309+
case FRAMEBUF_RGB565_LE:
285310
break;
286311
case FRAMEBUF_MHLSB:
287312
case FRAMEBUF_MHMSB:
@@ -306,7 +331,7 @@ STATIC mp_int_t framebuf_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo,
306331
(void)flags;
307332
mp_obj_framebuf_t *self = MP_OBJ_TO_PTR(self_in);
308333
bufinfo->buf = self->buf;
309-
bufinfo->len = self->stride * self->height * (self->format == FRAMEBUF_RGB565 ? 2 : 1);
334+
bufinfo->len = self->stride * self->height * bytes_per_pixel(self);
310335
bufinfo->typecode = 'B'; // view framebuf as bytes
311336
return 0;
312337
}
@@ -630,7 +655,13 @@ STATIC const mp_rom_map_elem_t framebuf_module_globals_table[] = {
630655
{ MP_ROM_QSTR(MP_QSTR_FrameBuffer1), MP_ROM_PTR(&legacy_framebuffer1_obj) },
631656
{ MP_ROM_QSTR(MP_QSTR_MVLSB), MP_ROM_INT(FRAMEBUF_MVLSB) },
632657
{ MP_ROM_QSTR(MP_QSTR_MONO_VLSB), MP_ROM_INT(FRAMEBUF_MVLSB) },
633-
{ MP_ROM_QSTR(MP_QSTR_RGB565), MP_ROM_INT(FRAMEBUF_RGB565) },
658+
#if MP_ENDIANNESS_BIG
659+
{ MP_ROM_QSTR(MP_QSTR_RGB565), MP_ROM_INT(FRAMEBUF_RGB565_BE) },
660+
#else
661+
{ MP_ROM_QSTR(MP_QSTR_RGB565), MP_ROM_INT(FRAMEBUF_RGB565_LE) },
662+
#endif
663+
{ MP_ROM_QSTR(MP_QSTR_RGB565_BE), MP_ROM_INT(FRAMEBUF_RGB565_BE) },
664+
{ MP_ROM_QSTR(MP_QSTR_RGB565_LE), MP_ROM_INT(FRAMEBUF_RGB565_LE) },
634665
{ MP_ROM_QSTR(MP_QSTR_GS2_HMSB), MP_ROM_INT(FRAMEBUF_GS2_HMSB) },
635666
{ MP_ROM_QSTR(MP_QSTR_GS4_HMSB), MP_ROM_INT(FRAMEBUF_GS4_HMSB) },
636667
{ MP_ROM_QSTR(MP_QSTR_GS8), MP_ROM_INT(FRAMEBUF_GS8) },

‎tests/extmod/framebuf16.py

Lines changed: 66 additions & 48 deletions
Original file line numberDiff line numberDiff line change
@@ -4,56 +4,74 @@
44
print("SKIP")
55
raise SystemExit
66

7-
def printbuf():
7+
8+
def printbuf(buf, w, h):
89
print("--8<--")
910
for y in range(h):
1011
print(buf[y * w * 2:(y + 1) * w * 2])
1112
print("-->8--")
1213

13-
w = 4
14-
h = 5
15-
buf = bytearray(w * h * 2)
16-
fbuf = framebuf.FrameBuffer(buf, w, h, framebuf.RGB565)
17-
18-
# fill
19-
fbuf.fill(0xffff)
20-
printbuf()
21-
fbuf.fill(0x0000)
22-
printbuf()
23-
24-
# put pixel
25-
fbuf.pixel(0, 0, 0xeeee)
26-
fbuf.pixel(3, 0, 0xee00)
27-
fbuf.pixel(0, 4, 0x00ee)
28-
fbuf.pixel(3, 4, 0x0ee0)
29-
printbuf()
30-
31-
# get pixel
32-
print(fbuf.pixel(0, 4), fbuf.pixel(1, 1))
33-
34-
# scroll
35-
fbuf.fill(0x0000)
36-
fbuf.pixel(2, 2, 0xffff)
37-
printbuf()
38-
fbuf.scroll(0, 1)
39-
printbuf()
40-
fbuf.scroll(1, 0)
41-
printbuf()
42-
fbuf.scroll(-1, -2)
43-
printbuf()
44-
45-
w2 = 2
46-
h2 = 3
47-
buf2 = bytearray(w2 * h2 * 2)
48-
fbuf2 = framebuf.FrameBuffer(buf2, w2, h2, framebuf.RGB565)
49-
50-
fbuf2.fill(0x0000)
51-
fbuf2.pixel(0, 0, 0x0ee0)
52-
fbuf2.pixel(0, 2, 0xee00)
53-
fbuf2.pixel(1, 0, 0x00ee)
54-
fbuf2.pixel(1, 2, 0xe00e)
55-
fbuf.fill(0xffff)
56-
fbuf.blit(fbuf2, 3, 3, 0x0000)
57-
fbuf.blit(fbuf2, -1, -1, 0x0000)
58-
fbuf.blit(fbuf2, 16, 16, 0x0000)
59-
printbuf()
14+
15+
def test_basic():
16+
w = 4
17+
h = 5
18+
buf = bytearray(w * h * 2)
19+
fbuf = framebuf.FrameBuffer(buf, w, h, framebuf.RGB565)
20+
21+
# fill
22+
fbuf.fill(0xffff)
23+
printbuf(buf, w, h)
24+
fbuf.fill(0x0000)
25+
printbuf(buf, w, h)
26+
27+
# put pixel
28+
fbuf.pixel(0, 0, 0xeeee)
29+
fbuf.pixel(3, 0, 0xee00)
30+
fbuf.pixel(0, 4, 0x00ee)
31+
fbuf.pixel(3, 4, 0x0ee0)
32+
printbuf(buf, w, h)
33+
34+
# get pixel
35+
print(fbuf.pixel(0, 4), fbuf.pixel(1, 1))
36+
37+
# scroll
38+
fbuf.fill(0x0000)
39+
fbuf.pixel(2, 2, 0xffff)
40+
printbuf(buf, w, h)
41+
fbuf.scroll(0, 1)
42+
printbuf(buf, w, h)
43+
fbuf.scroll(1, 0)
44+
printbuf(buf, w, h)
45+
fbuf.scroll(-1, -2)
46+
printbuf(buf, w, h)
47+
48+
w2 = 2
49+
h2 = 3
50+
buf2 = bytearray(w2 * h2 * 2)
51+
fbuf2 = framebuf.FrameBuffer(buf2, w2, h2, framebuf.RGB565)
52+
53+
fbuf2.fill(0x0000)
54+
fbuf2.pixel(0, 0, 0x0ee0)
55+
fbuf2.pixel(0, 2, 0xee00)
56+
fbuf2.pixel(1, 0, 0x00ee)
57+
fbuf2.pixel(1, 2, 0xe00e)
58+
fbuf.fill(0xffff)
59+
fbuf.blit(fbuf2, 3, 3, 0x0000)
60+
fbuf.blit(fbuf2, -1, -1, 0x0000)
61+
fbuf.blit(fbuf2, 16, 16, 0x0000)
62+
printbuf(buf, w, h)
63+
64+
65+
def test_endian():
66+
for endian in (framebuf.RGB565_BE, framebuf.RGB565_LE,):
67+
w = 4
68+
h = 4
69+
buf = bytearray(w * h * 2)
70+
fbuf = framebuf.FrameBuffer(buf, w, h, endian)
71+
fbuf.fill_rect(1, 1, 2, 2, 0xabcd)
72+
fbuf.pixel(2, 2, 0xdcba)
73+
printbuf(buf, w, h)
74+
75+
76+
test_basic()
77+
test_endian()

‎tests/extmod/framebuf16.py.exp

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -55,3 +55,15 @@ bytearray(b'\xff\xff\xff\xff\xff\xff\xff\xff')
5555
bytearray(b'\xff\xff\xff\xff\xff\xff\xe0\x0e')
5656
bytearray(b'\xff\xff\xff\xff\xff\xff\xff\xff')
5757
-->8--
58+
--8<--
59+
bytearray(b'\x00\x00\x00\x00\x00\x00\x00\x00')
60+
bytearray(b'\x00\x00\xab\xcd\xab\xcd\x00\x00')
61+
bytearray(b'\x00\x00\xab\xcd\xdc\xba\x00\x00')
62+
bytearray(b'\x00\x00\x00\x00\x00\x00\x00\x00')
63+
-->8--
64+
--8<--
65+
bytearray(b'\x00\x00\x00\x00\x00\x00\x00\x00')
66+
bytearray(b'\x00\x00\xcd\xab\xcd\xab\x00\x00')
67+
bytearray(b'\x00\x00\xcd\xab\xba\xdc\x00\x00')
68+
bytearray(b'\x00\x00\x00\x00\x00\x00\x00\x00')
69+
-->8--

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