Copied only necessary decoding functions from the lodepng opensource.
See: https://lodev.org/lodepng/
additional changes:
- disabled crc for the optimal size.
- converted the format bgr -> rgb for our png example.
Still we don't have a concrete idea for the image formats,
We should fix the converting methods between bgra <-> rgba.
@Issue: https://github.com/Samsung/thorvg/issues/594
This patch has 2 purposes,
1. revise the loaders infrastructure to support both static/external linking loaders.
2. add a template for static jpg/png loaders after external jpg/png.
Our default loaders prefer static linking, external loaders are only available
when dependent libraries on the build system are found.
You might wonder why we have the external loaders together,
they might be faster than static loaders since the popular libraries are likely to be well maintained,
fine-grained optimized.
Thus in this patch, meson tries to apply the external loaders first
then see if the dependencies were found or not,
if it's failed, it turns to the default static loaders.
Next this patch, we need the contribution for actual static jpg/png loaders implementation.
@Issue: https://github.com/Samsung/thorvg/issues/594