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3 commits

Author SHA1 Message Date
Lucas CHOLLET
05c8ad4e91 LibGfx/JPEG: Write quantization tables in the zigzag ordering 
This is clearly something I missed during the first implementation. The
specification is crystal clear about it: "The quantization elements
shall be specified in zig-zag scan order."

This patch fixes the weird behavior we had when using the quantization
table.
 2023-07-04 00:01:06 +02:00
Lucas CHOLLET
cc1bd2d2d9 LibGfx/JPEG: Use a look-up table for cosine values 
This solution is a middle ground between re-computing `cos` every time
and a much more mathematically complicated approach (as we have in the
decoder).

While still being far from optimal it already gives us a 10x
improvement, not that bad :^)

Co-authored-by: Tim Flynn <trflynn89@pm.me>
 2023-06-25 00:22:21 +02:00
Lucas CHOLLET
226b214142 LibGfx/JPEG: Add a JPEG encoder :^) 
This encoder is very naive as it only output SOF0 images and uses
pre-defined Huffman tables.

There is also a small bug with quantization which make using it
over-degrade the quality.
 2023-06-22 21:13:04 +02:00