Re: [PATCH v3 0/6] MR7711: d3dx9: Rework color key handling.

[Matteo Bruni (＠Mystral)]

Matteo Bruni (@Mystral) commented about dlls/d3dx9_36/surface.c:
> -
> -
>        unique_values = (1u << channel_bits) - 2;
> -
>        channel_conv = (channel_conv * 2.0f) - 1.0f;
> -
>        channel_conv = ((int8_t)(channel_conv * max_value + 0.5f)) / (float)max_value;
> -
>        channel_conv = (channel_conv + 1.0f) / 2.0f;
> -
>    }
> -
>    else
> -
>    {
> -
>        unique_values = (1u << channel_bits) - 1;
> -
>        channel_conv = ((uint8_t)(channel_conv * unique_values + 0.5f)) / unique_values;
> -
>    }
> -
> -
>    channel_conv = channel_conv * 255.0f + 0.5f;
> -
>    slop = ((255.0f - unique_values) / unique_values) / 2.0f;
> -
>    color_key_out->color_key_min[i] = d3dx_clamp(channel_conv - slop, 0.0f, 255.0f);
> -
>    color_key_out->color_key_max[i] = d3dx_clamp(channel_conv + slop, 0.0f, 255.0f);

Similarly here:
```
        channel_conv = channel_conv * 255.0f;
        slop = (255.0f - unique_values) / unique_values / 2.0f;
        color_key_out->color_key_min[i] = rintf(d3dx_clamp(channel_conv - slop, 0.0f, 255.0f));
        color_key_out->color_key_max[i] = rintf(d3dx_clamp(channel_conv + slop, 0.0f, 255.0f));
```
The whole conversion math is quite questionable, but the results seem to match native pretty closely so I guess it is what it is :sweat_smile: