[libcamera-devel] [PATCH v4 2/4] libcamera: rkisp1: Crop on ISP before downscaling

[Kieran Bingham]

Quoting Jacopo Mondi via libcamera-devel (2023-03-21 17:20:02)
> Crop on the resizer sink pad before downscaling to the aspect ratio
> of the desired output size.
> 
> Cropping the input frame to the output aspect ratio allows to maintain
> the correct picture proportions, as otherwise downscaling would change
> the image geometry.
> 
> Signed-off-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> ---
>  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> index 5079b268c464..5547cc32b6ca 100644
> --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> @@ -314,7 +314,10 @@ int RkISP1Path::configure(const StreamConfiguration &config,
>         if (ret < 0)
>                 return ret;
>  
> -       Rectangle rect(0, 0, ispFormat.size);
> +       /* Crop on the resizer input to maintain FOV before downscaling */
> +       Size ispCrop = inputFormat.size.boundedToAspectRatio(config.size)
> +                                      .alignedUpTo(2, 2);
> +       Rectangle rect(ispCrop);

Should this be centered ? Otherwise I can imagine a letterbox effect at
the *top* of the image, or a left aligned rectangle?


>         ret = resizer_->setSelection(0, V4L2_SEL_TGT_CROP, &rect);
>         if (ret < 0)
>                 return ret;
> -- 
> 2.40.0
>