Lvgl snapshot_take

Micropython
1

I am wanting to snapshot the current display. It seems to mostly work, but I’m only getting part of the image. Maybe because of double buffering? Is there a better way? I am running on ESP32 with ST7735 driver. The screen is currently set to a green background, which seems to be about right in the captured image.

import lvgl as lv
import utime

lv.init()

# Global variable to store the pixel data
snapshot = None

def take(file_name="/app/mcc/images/snapshot.bin"):
    global snapshot  # Indicate that we're using the global variable

    scr = lv.screen_active()

    # Take a snapshot of the screen
    start_time = utime.ticks_us()
    snapshot = lv.snapshot_take(scr, lv.COLOR_FORMAT.NATIVE)

    end_time = utime.ticks_us()
    #print(f"Snapshot taken in {utime.ticks_diff(end_time, start_time)} microseconds")

image


Edit:

Image has now changed to all noise.
2

I’ve now changed the background to blue. The blue sorta moves up and down? Occasionally filling the buffer, and then being emptied.

image

3

Created bug ticket:

4

lv.snapshot_take works fine. The problem is/was getting the data out of the snapshot. it’s a C Array uint8[]. I need to get it into a bytearray response for a httpserver.

response = bytearray(snapshot.snapshot.data_size)
for i in range(snapshot.snapshot.data_size):
response[i] = snapshot.snapshot.data[I]

This works well enough, but it’s slow. Can you recommend a fast way to use the snapshot? I tried uctypes.bytes_at, but that is what was giving me the noise above.

5

I’ve tested the snapshot and I can confirm it really works.

Unfortunately I cannot comment on the MicroPython part. :frowning: