How to specify the mimeType when using a ShareLink?

When I try to share a image of a component using the ImageRenderer, the type is not .png while sharing the image created using ShareLink

(The type is .jpeg for some reasons...)

My code looks like this:

ShareLink(
    "Share",
    item:  (
        ImageRenderer(
            content: shareView.frame(
                width: 420,
                height: 520
            )
        ).uiImage?.pngData()
    )!,
    preview: SharePreview(
        "Share Preview",
        image: (
            ImageRenderer(
                content: shareView.frame(
                    width: 420,
                    height: 520
                )
            ).uiImage?.pngData()
        )!
          )
)

Also the image shared is always in low resolution, if anyone knows what to do in this case let me know!

Any helps will be appreciated!