bug with LODEPNG_COMPILE_ALLOCATORS option about lv_lib_png

[embeddedt]

We have also seen strangely high amounts of memory being used by lodepng in the MicroPython simulator so this seems to correlate with that. It would be great if a newer version of lodepng solved the issue.

(cc @amirgon)

[kisvegabor]

Thanks for the report!

In fact, I found that lv_lib_png is using "20180611" release. lodepng is now "20201017"

Would you be interested in sending a PR with the latest version?
I think the most important change was added in this commit: 66b6642

[alsaleem00]

I found that lodepng consumes (194KB, including the 37KB file size and 64KB image buffer). The file was only 128x128 pixels.
That was a lot of memory for ESP32. I used pngle to decode png which consumes less,
However, pngle failed when i allocated memory from SPIRAM, while lodepng did not.

The new lodepng changed the code so that user can use his own memory allocation.

Let me check to evaluate the amount of work needed to use new lodepng in lv_lib_png. I will follow the same approach you used for the old one.

[alsaleem00]

Here is a log of memory allocation activities by lodepng (attached), both 2018 and 2020 versions.
There is some reduction in memory usage but still high.

lodepng_mem_2018.txt
lodepng_mem_2020.txt

[alsaleem00]

lv_lib_png is now using lodepng newest release. So, this thread should be closed..

[kisvegabor]

Thank you!