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why does the frambuf cannot use a memoryview as buf?
Posted: Sun Mar 13, 2022 1:37 pm
by NikS
Hi,
the background of this question is that i believe the following code does allocate a new bytearray for every char it draws.
Code: Select all
for i in range(len(text)):
glyph, H, W = self.font.get_ch(text[i])
cb = framebuf.FrameBuffer( bytearray(glyph[0:len(glyph)]) , W, H, framebuf.MONO_HLSB)
self.fb.blit(cb, o, 0)
o=o+W
if i change the code to:
Code: Select all
for i in range(len(text)):
glyph, H, W = self.font.get_ch(text[i])
cb = framebuf.FrameBuffer( glyph[0:len(glyph)] , W, H, framebuf.MONO_HLSB)
self.fb.blit(cb, o, 0)
o=o+W
it fails with: TypeError: object with buffer protocol required
Re: why does the frambuf cannot use a memoryview as buf?
Posted: Sun Mar 13, 2022 5:49 pm
by pythoncoder
You might like to study
this code.
Re: why does the frambuf cannot use a memoryview as buf?
Posted: Sun Mar 13, 2022 7:33 pm
by NikS
Hi Peter,
thank you very much. Being able to read is a clear advantage
though it's not really faster, it consumes less memory.
Nik
Code: Select all
# memoryview - test
from utime import sleep_ms, ticks_ms, ticks_us, ticks_diff
from uctypes import bytearray_at, addressof
def test():
random_byte_array = bytearray('ABCDE1234567890', 'utf-8')
mv = memoryview(random_byte_array)
start = ticks_us()
for i in range(70,80):
mv[1]=i
a = bytearray_at(addressof(mv), len(mv)) # create bytearray from memory view without copy
#a=bytearray(mv[0:len(mv)]) # this copies
#print(bytearray(mv[0:10]), a)
#print (" show in ", stop, "us mem:", gc.mem_free())
stop=ticks_us()-start
print (" show in ", stop, "us mem:", gc.mem_free())
gc.collect()
gc.mem_free()
test()
Re: why does the frambuf cannot use a memoryview as buf?
Posted: Mon Mar 14, 2022 11:37 am
by pythoncoder
it consumes less memory
That is the point. The Python fonts are designed to reside in Flash. Using a memoryview enables a glyph to be accessed with minimal RAM use.
The fonts will work when loaded normally, but freezing them in Flash results in major RAM savings.
Re: why does the frambuf cannot use a memoryview as buf?
Posted: Mon Mar 14, 2022 11:48 pm
by c22
I stumbled upon the same buffer protocol problem, albeit aiming to a different target:
viewtopic.php?f=15&t=9211
There's currently no proper solution, I had to make a compromise on RAM usage to achive an acceptable result. Maybe my topic contains something useful to you.