[help-needed] MKS TFT thumbnails

[adripo]

Implementation of MKS TFT thumbnails for other printers than Biqu.
I was inspired by this PR ArtificalSUN/MKS-WIFI_PS_uploader#5 but I don't have much experience in c++.

I would like to get some help to convert the logic that can be found here:
https://github.com/Jeredian/mks-wifi-plugin/blob/develop/MKSPreview.py#L21
and here
https://github.com/SH1NZ33/MKS-WIFI_PS_uploader/blob/patch-1/MKS_WIFI_PS_upload.pyw#L31

For the moment I copied the conversion from Biqu.
The sections that need to be checked and edited are:

• https://github.com/adripo/SuperSlicer/blob/tft-thumbnails/src/libslic3r/GCode/Thumbnails.hpp#L59 from 59 to 78
• https://github.com/adripo/SuperSlicer/blob/tft-thumbnails/src/libslic3r/GCode/Thumbnails.cpp#L84 from 84 to 119

I can test any file on my FlyingBear 4S.

fix #3064

[adripo]

The previews are visible, but the colors are not correct. Here are some examples:

original:

preview:

thumbnail:

[supermerill]

can you try instead of

            uint16_t pixel = 0;
            //r
            pixel |= uint16_t((rgba_pixels[y * row_size + x * 4 + 0 ] & 0x000000F8) >> 3);
            //g
            pixel |= uint16_t((rgba_pixels[y * row_size + x * 4 + 1 ] & 0x000000FC) << 3);
            //b
            pixel |= uint16_t((rgba_pixels[y * row_size + x * 4 + 2 ] & 0x000000F8) << 8);
            tohex << std::setw(4) << pixel;

to use

            uint16_t pixel = 0;
            //r
            pixel |= uint16_t(((rgba_pixels[y * row_size + x * 4 + 0 ] & 0x000000FF) >> 3) << 11);
            //g
            pixel |= uint16_t(((rgba_pixels[y * row_size + x * 4 + 1 ] & 0x000000FF)  >> 2) <<5);
            //b
            pixel |= uint16_t((rgba_pixels[y * row_size + x * 4 + 2 ] & 0x000000FF) >> 3);
            tohex << std::setw(4) << pixel;

[supermerill]

also it seems you didn't pushed a working version, as it doesn't compile