fix(cli): preserve original image bytes when asset!() requests no transform (#5642)

[singhlovepreet9]

Fixes #5642.

Problem

asset!("image.png") with no options re-encodes the image by default, which can significantly increase the size of an already-optimized PNG (the issue reports 193K → 976K).

Root cause

An option-less asset!(...) resolves to ImageAssetOptions::default() = format: ImageFormat::Unknown, size: ImageSize::Automatic. In process_image, format() == Unknown falls into the catch-all (Ok(image), _) => image.save(output_path) arm, which decodes and re-encodes the image with the image crate's default PNG encoder — no optimization, and larger output for already-optimized sources.

Fix

Add an early guard in process_image: when no output format conversion and no manual resize are requested (Unknown + Automatic), copy the source bytes verbatim (the asset is still content-hashed by filename) instead of decoding and re-encoding. This matches the expected behavior in the issue — preserve the original bytes unless image processing is explicitly requested.

Explicit .with_format(...) / .with_size(...) paths are unchanged: those still resize/convert/optimize as before.

if image_options.format() == ImageFormat::Unknown
    && image_options.size() == ImageSize::Automatic
{
    std::fs::copy(source, output_path)?;
    return Ok(());
}

Test

Added opt::image::tests::default_options_preserve_source_bytes: it writes a Best-compressed source PNG carrying a tEXt chunk (which a decode→re-encode drops), runs process_image with default options, and asserts the output is byte-identical to the source — so the test fails if the default path ever re-encodes again.

test opt::image::tests::default_options_preserve_source_bytes ... ok

Ran with cargo +1.93.0 test -p dioxus-cli (repo MSRV 1.93).

---

Note: @GPNaslund mentioned interest in the issue — happy to defer if they already have a fix in flight; posting this since no PR was up.

[WaterWhisperer]

It looks like AI-generated explanatory text that was submitted without sufficient review or cleanup. Six lines of comments narrating such a simple guard in a small function is unreasonable.

[singhlovepreet9]

Thanks for the feedback! You're completely right—the comment was unnecessarily verbose.I've shortened the comments to a single line, squashed the commits, and updated the PR. Let me know if everything looks good now!