Micropython MemoryError when trying to get image from URL - micropython

Question

Hi I’ve bought the dispay pack2 (https://shop.pimoroni.com/products/pico-display-pack-2-0?variant=39374122582099) and am trying to display an image. If I download the image and put it on the pi pico w then the image displays OK. I’m trying to get the image to be downloaded from a URL and displayed but am getting
MemoryError: memory allocation failed, allocating 21760 bytes
I’m new to this sort of coding and am struggling to see what I’m doing wrong. here is my full py code
`
import network
import urequests
import time
import picographics
import jpegdec
from pimoroni import Button
wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect("SSID","password")
time.sleep(5)
print(wlan.isconnected())
display = picographics.PicoGraphics(display=picographics.DISPLAY_PICO_DISPLAY_2, rotate=0)
display.set_backlight(0.8)
# Create a new JPEG decoder for our PicoGraphics
j = jpegdec.JPEG(display)
# Open the JPEG file
#j.open_file("squid.jpg")
# Decode the JPEG
#j.decode(0, 0, jpegdec.JPEG_SCALE_FULL)
if wlan.isconnected():
res = urequests.get(url='https://squirrel365.io/tmp/squid.jpg')
j.open_RAM(memoryview(res.content))
# Decode the JPEG
j.decode(0, 0, jpegdec.JPEG_SCALE_FULL)
# Display the result
display.update()
`
Any ideas?
Kedge
I've tested and can get plain text back from the URL, as soon as I try and get an image I get the memory error

Answer 1

You're not doing anything "wrong"; you're just working with a device that has very limited resources. What if you re-arrange your code to perform the fetch before initializing any graphics resources, write the data to a file, and then have the jpeg module read it from disk? Something like:
import jpegdec
import network
import picographics
import time
import urequests
wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect("SSID","password")
while not wlan.isconnected():
print('waiting for network')
time.sleep(1)
res = urequests.get(url='https://squirrel365.io/tmp/squid.jpg')
with open('squid.jpg', 'wb') as fd:
fd.write(res.content)
display = picographics.PicoGraphics(display=picographics.DISPLAY_PICO_DISPLAY_2, rotate=0)
display.set_backlight(0.8)
# Create a new JPEG decoder for our PicoGraphics
j = jpegdec.JPEG(display)
# Open the JPEG file
j.open_file("squid.jpg")
# Decode the JPEG
j.decode(0, 0, jpegdec.JPEG_SCALE_FULL)
# Display the result
display.update()
You can sometimes free up additional memory by adding an explicit garbage collection to your code:
import gc
.
.
.
with open('squid.jpg', 'wb') as fd:
fd.write(res.content)
gc.collect()