Function convert 

pub fn convert(
    frame: &FrameEnvelope,
    target: PixelFormat,
) -> Result<FrameEnvelope, ConvertError>

Convert a frame to a different pixel format.

Works with host-resident and MappableToHost device frames. Conversion always allocates a new output buffer, so the additional cost of materializing device data is negligible.

Errors

• ConvertError::SameFormat — source already matches target; clone instead.
• ConvertError::Unsupported — no conversion path for this format pair.
• ConvertError::Access — host bytes could not be obtained (opaque device frame).

Currently supported paths:

• Bgr8 → Rgb8
• Rgb8 → Bgr8
• Rgba8 → Rgb8
• Rgb8 → Gray8

Other conversions can be contributed by adding a match arm below.