I figured out that I should not have done that (mip.install(...)) and I’ve removed the created .micropython directory from my home folder.
By only copying the encoding part of the jpeg library directly into my script, it works as intended.
Here is the full script if anyone needs screenshots:
import lvgl as lv
from struct import pack
# import jpeg
# copy-pasta from jpeg
_z_z = bytes([ # Zig-zag indices of AC coefficients
1, 8, 16, 9, 2, 3, 10, 17, 24, 32, 25, 18, 11, 4, 5,
12, 19, 26, 33, 40, 48, 41, 34, 27, 20, 13, 6, 7, 14, 21, 28,
35, 42, 49, 56, 57, 50, 43, 36, 29, 22, 15, 23, 30, 37, 44, 51,
58, 59, 52, 45, 38, 31, 39, 46, 53, 60, 61, 54, 47, 55, 62, 63])
_luminance_quantization = bytes([ # Luminance quantization table in zig-zag order
16, 11, 12, 14, 12, 10, 16, 14, 13, 14, 18, 17, 16, 19, 24, 40,
26, 24, 22, 22, 24, 49, 35, 37, 29, 40, 58, 51, 61, 60, 57, 51,
56, 55, 64, 72, 92, 78, 64, 68, 87, 69, 55, 56, 80,109, 81, 87,
95, 98,103,104,103, 62, 77,113,121,112,100,120, 92,101,103, 99])
_chrominance_quantization = bytes([ # Chrominance quantization table in zig-zag order
17, 18, 18, 24, 21, 24, 47, 26, 26, 47, 99, 66, 56, 66, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99])
_ld_lengths = bytes([ # Luminance DC code lengths
0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0])
_ld_values = bytes([ # Luminance DC values
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11])
_la_lengths = bytes([ # Luminance AC code lengths
0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 125])
_la_values = bytes([ # Luminance AC values
1, 2, 3, 0, 4, 17, 5, 18, 33, 49, 65, 6, 19, 81, 97, 7, 34,113,
20, 50,129,145,161, 8, 35, 66,177,193, 21, 82,209,240, 36, 51, 98,114,
130, 9, 10, 22, 23, 24, 25, 26, 37, 38, 39, 40, 41, 42, 52, 53, 54, 55,
56, 57, 58, 67, 68, 69, 70, 71, 72, 73, 74, 83, 84, 85, 86, 87, 88, 89,
90, 99,100,101,102,103,104,105,106,115,116,117,118,119,120,121,122,131,
132,133,134,135,136,137,138,146,147,148,149,150,151,152,153,154,162,163,
164,165,166,167,168,169,170,178,179,180,181,182,183,184,185,186,194,195,
196,197,198,199,200,201,202,210,211,212,213,214,215,216,217,218,225,226,
227,228,229,230,231,232,233,234,241,242,243,244,245,246,247,248,249,250])
_cd_lengths = bytes([ # Chrominance DC code lengths
0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0])
_cd_values = bytes([ # Chrominance DC values
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11])
_ca_lengths = bytes([ # Chrominance AC code lengths
0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 119])
_ca_values = bytes([ # Chrominance AC values
0, 1, 2, 3, 17, 4, 5, 33, 49, 6, 18, 65, 81, 7, 97,113, 19, 34,
50,129, 8, 20, 66,145,161,177,193, 9, 35, 51, 82,240, 21, 98,114,209,
10, 22, 36, 52,225, 37,241, 23, 24, 25, 26, 38, 39, 40, 41, 42, 53, 54,
55, 56, 57, 58, 67, 68, 69, 70, 71, 72, 73, 74, 83, 84, 85, 86, 87, 88,
89, 90, 99,100,101,102,103,104,105,106,115,116,117,118,119,120,121,122,
130,131,132,133,134,135,136,137,138,146,147,148,149,150,151,152,153,154,
162,163,164,165,166,167,168,169,170,178,179,180,181,182,183,184,185,186,
194,195,196,197,198,199,200,201,202,210,211,212,213,214,215,216,217,218,
226,227,228,229,230,231,232,233,234,242,243,244,245,246,247,248,249,250])
def _quantization_table(table, quality):
quality = max(0, min(quality, 100))
if quality < 50:
q = 5000//quality
else:
q = 200 - quality*2
return bytes([max(1, min((i*q + 50)//100, 255)) for i in table])
def _huffman_table(lengths, values):
table = [None]*(max(values) + 1)
code = 0
i = 0
size = 1
for a in lengths:
for j in range(a):
table[values[i]] = code, size
code += 1
i += 1
code *= 2
size += 1
return table
def _scale_factor(table):
factor = [0]*64
factor[0] = table[0]*8
i = 1
for z in _z_z:
factor[z] = table[i]*8
i += 1
return factor
def _marker_segment(marker, data):
return b'\xff' + marker + pack('>H', len(data) + 2) + data
def _forward_dct(block):
# Ref.: Independent JPEG Group's "jfdctint.c", v8d
# Copyright (C) 1994-1996, Thomas G. Lane
# Modification developed 2003-2009 by Guido Vollbeding
for i in range(0, 64, 8):
tmp0 = block[i] + block[i+7]
tmp1 = block[i+1] + block[i+6]
tmp2 = block[i+2] + block[i+5]
tmp3 = block[i+3] + block[i+4]
tmp10 = tmp0 + tmp3
tmp12 = tmp0 - tmp3
tmp11 = tmp1 + tmp2
tmp13 = tmp1 - tmp2
tmp0 = block[i] - block[i+7]
tmp1 = block[i+1] - block[i+6]
tmp2 = block[i+2] - block[i+5]
tmp3 = block[i+3] - block[i+4]
block[i] = (tmp10 + tmp11 - 8*128) << 2 # PASS1_BITS
block[i+4] = (tmp10 - tmp11) << 2
z1 = (tmp12 + tmp13)*4433 # FIX_0_541196100
z1 += 1024 # 1 << (CONST_BITS-PASS1_BITS-1)
block[i+2] = (z1 + tmp12*6270) >> 11 # FIX_0_765366865
block[i+6] = (z1 - tmp13*15137) >> 11 # FIX_1_847759065
tmp10 = tmp0 + tmp3
tmp11 = tmp1 + tmp2
tmp12 = tmp0 + tmp2
tmp13 = tmp1 + tmp3
z1 = (tmp12 + tmp13)*9633 # FIX_1_175875602
z1 += 1024 # 1 << (CONST_BITS-PASS1_BITS-1)
tmp0 = tmp0*12299 # FIX_1_501321110
tmp1 = tmp1*25172 # FIX_3_072711026
tmp2 = tmp2*16819 # FIX_2_053119869
tmp3 = tmp3*2446 # FIX_0_298631336
tmp10 = tmp10*-7373 # FIX_0_899976223
tmp11 = tmp11*-20995 # FIX_2_562915447
tmp12 = tmp12*-3196 # FIX_0_390180644
tmp13 = tmp13*-16069 # FIX_1_961570560
tmp12 += z1
tmp13 += z1
block[i+1] = (tmp0 + tmp10 + tmp12) >> 11
block[i+3] = (tmp1 + tmp11 + tmp13) >> 11
block[i+5] = (tmp2 + tmp11 + tmp12) >> 11
block[i+7] = (tmp3 + tmp10 + tmp13) >> 11
for i in range(8):
tmp0 = block[i] + block[i+56]
tmp1 = block[i+8] + block[i+48]
tmp2 = block[i+16] + block[i+40]
tmp3 = block[i+24] + block[i+32]
tmp10 = tmp0 + tmp3 + 2 # 1 << (PASS1_BITS-1)
tmp12 = tmp0 - tmp3
tmp11 = tmp1 + tmp2
tmp13 = tmp1 - tmp2
tmp0 = block[i] - block[i+56]
tmp1 = block[i+8] - block[i+48]
tmp2 = block[i+16] - block[i+40]
tmp3 = block[i+24] - block[i+32]
block[i] = (tmp10 + tmp11) >> 2 # PASS1_BITS
block[i+32] = (tmp10 - tmp11) >> 2
z1 = (tmp12 + tmp13)*4433 # FIX_0_541196100
z1 += 16384 # 1 << (CONST_BITS+PASS1_BITS-1)
block[i+16] = (z1 + tmp12*6270) >> 15 # FIX_0_765366865, CONST_BITS+PASS1_BITS
block[i+48] = (z1 - tmp13*15137) >> 15 # FIX_1_847759065
tmp10 = tmp0 + tmp3
tmp11 = tmp1 + tmp2
tmp12 = tmp0 + tmp2
tmp13 = tmp1 + tmp3
z1 = (tmp12 + tmp13)*9633 # FIX_1_175875602
z1 += 16384 # 1 << (CONST_BITS+PASS1_BITS-1)
tmp0 = tmp0*12299 # FIX_1_501321110
tmp1 = tmp1*25172 # FIX_3_072711026
tmp2 = tmp2*16819 # FIX_2_053119869
tmp3 = tmp3*2446 # FIX_0_298631336
tmp10 = tmp10*-7373 # FIX_0_899976223
tmp11 = tmp11*-20995 # FIX_2_562915447
tmp12 = tmp12*-3196 # FIX_0_390180644
tmp13 = tmp13*-16069 # FIX_1_961570560
tmp12 += z1
tmp13 += z1
block[i+8] = (tmp0 + tmp10 + tmp12) >> 15 # CONST_BITS+PASS1_BITS
block[i+24] = (tmp1 + tmp11 + tmp13) >> 15
block[i+40] = (tmp2 + tmp11 + tmp12) >> 15
block[i+56] = (tmp3 + tmp10 + tmp13) >> 15
class _entropy_encoder(object):
def __init__(self):
c = [i for j in reversed(range(16)) for i in range(1 << j)]
s = [j for j in range(1, 16) for i in range(1 << (j - 1))]
s = [0] + s + list(reversed(s))
self.codes, self.sizes = c, s
self.value, self.length = 0, 0
self.data = bytearray()
def encode(self, previous, block, scale, dc, ac):
_forward_dct(block)
for i in range(64):
block[i] = (((block[i] << 1)//scale[i]) + 1) >> 1
d = block[0] - previous
if d == 0:
self.write(*dc[0])
else:
s = self.sizes[d]
self.write(*dc[s])
self.write(self.codes[d], s)
n = 0
for i in _z_z:
if block[i] == 0:
n += 1
else:
while n > 15:
self.write(*ac[0xf0])
n -= 16
s = self.sizes[block[i]]
self.write(*ac[n*16 + s])
self.write(self.codes[block[i]], s)
n = 0
if n > 0:
self.write(*ac[0])
return block[0]
def write(self, value, length):
data = self.data
value += (self.value << length)
length += self.length
while length > 7:
length -= 8
v = (value >> length) & 0xff
if v == 0xff:
data.append(0xff)
data.append(0)
else:
data.append(v)
self.value = value & 0xff
self.length = length
def dump(self):
return self.data
class image():
def __init__(self, width: int, height: int, kind: str, data: bytes):
if kind not in ('g', 'rgb', 'cmyk'):
raise ValueError('Invalid image kind.')
self.width = width
self.height = height
self.kind = kind
self.n = 1 if kind == 'g' else 3 if kind == 'rgb' else 4
self.data = data
def serialize(image, quality):
w, h, n, data = image.width, image.height, image.n, image.data
ydc = udc = vdc = kdc = 0
yblock, ublock, vblock, kblock = [0]*64, [0]*64, [0]*64, [0]*64
lq = _quantization_table(_luminance_quantization, quality)
ld = _huffman_table(_ld_lengths, _ld_values)
la = _huffman_table(_la_lengths, _la_values)
ls = _scale_factor(lq)
if n == 3:
cq = _quantization_table(_chrominance_quantization, quality)
cd = _huffman_table(_cd_lengths, _cd_values)
ca = _huffman_table(_ca_lengths, _ca_values)
cs = _scale_factor(cq)
e = _entropy_encoder()
for y in range(0, h, 8):
for x in range(0, w, 8):
i = 0
for yy in range(y, y + 8):
for xx in range(x, x + 8):
j = (min(xx, w - 1) + min(yy, h - 1)*w)*n
if n == 1:
yblock[i] = data[j]
elif n == 3:
r, g, b = data[j], data[j + 1], data[j + 2]
yblock[i] = (19595*r + 38470*g + 7471*b + 32768) >> 16
ublock[i] = (-11056*r - 21712*g + 32768*b + 8421376) >> 16
vblock[i] = (32768*r - 27440*g - 5328*b + 8421376) >> 16
else: # n == 4
yblock[i] = data[j]
ublock[i] = data[j + 1]
vblock[i] = data[j + 2]
kblock[i] = data[j + 3]
i += 1
ydc = e.encode(ydc, yblock, ls, ld, la)
if n == 3:
udc = e.encode(udc, ublock, cs, cd, ca)
vdc = e.encode(vdc, vblock, cs, cd, ca)
elif n == 4:
udc = e.encode(udc, ublock, ls, ld, la)
vdc = e.encode(vdc, vblock, ls, ld, la)
kdc = e.encode(kdc, kblock, ls, ld, la)
e.write(0x7f, 7) # padding
app = b'Adobe\0\144\200\0\0\0\0' # tag, version, flags0, flags1, transform
sof = b'\10' + pack('>HHB', h, w, n) + b'\1\21\0' # depth, id, sampling, qtable
sos = pack('B', n) + b'\1\0' # id, htable
dqt = b'\0' + lq
dht = b'\0' + _ld_lengths + _ld_values + b'\20' + _la_lengths + _la_values
if n == 3:
sof += b'\2\21\1\3\21\1'
sos += b'\2\21\3\21'
dqt += b'\1' + cq
dht += b'\1' + _cd_lengths + _cd_values + b'\21' + _ca_lengths + _ca_values
elif n == 4:
sof += b'\2\21\0\3\21\0\4\21\0'
sos += b'\2\0\3\0\4\0'
sos += b'\0\77\0' # start, end, approximation
return b''.join([
b'\xff\xd8', # SOI
_marker_segment(b'\xee', app) if n == 4 else b'',
_marker_segment(b'\xdb', dqt),
_marker_segment(b'\xc0', sof),
_marker_segment(b'\xc4', dht),
_marker_segment(b'\xda', sos),
e.dump(),
b'\xff\xd9']) # EOI
def bgr_to_rgb(data):
# Assume data is a flat bytearray in BGR format
for i in range(0, len(data), 3):
data[i], data[i+2] = data[i+2], data[i] # Swap the B and R values
return data
def take_screenshot(container, output_file):
snapshot = lv.snapshot_take(container, lv.COLOR_FORMAT.NATIVE)
data_size = snapshot.data_size
buffer = snapshot.data.__dereference__(data_size)
img = image(container.get_width(), container.get_height(), "rgb", bgr_to_rgb(buffer))
with open(output_file, 'wb') as f:
f.write(serialize(img, 100))
Keep in mind that I have compiled LVGL micropython using
#define LV_USE_STDLIB_MALLOC LV_STDLIB_CLIB
My intention is to run it only on the Unix port anyways. Running this on hardware might actually not be feasible memory-wise.