[libcamera-devel] [PATCH v6 6/7] libcamera: Add validateColorSpaces to CameraConfiguration class

[Umang Jain]

Hi David,

One clarification below please,

On 11/18/21 8:49 PM, David Plowman wrote:
> This method forces raw streams to have the "raw" color space, and also
> optionally makes all output streams to share the same color space as
> some platforms may require this.
>
> Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> ---
>   include/libcamera/camera.h |  2 ++
>   src/libcamera/camera.cpp   | 51 ++++++++++++++++++++++++++++++++++++++
>   2 files changed, 53 insertions(+)
>
> diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h
> index 601ee46e..fdab4410 100644
> --- a/include/libcamera/camera.h
> +++ b/include/libcamera/camera.h
> @@ -69,6 +69,8 @@ public:
>   protected:
>   	CameraConfiguration();
>   
> +	Status validateColorSpaces(bool sharedColorSpace);
> +
>   	std::vector<StreamConfiguration> config_;
>   };
>   
> diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
> index 400a7cf0..c1541685 100644
> --- a/src/libcamera/camera.cpp
> +++ b/src/libcamera/camera.cpp
> @@ -20,6 +20,7 @@
>   
>   #include "libcamera/internal/camera.h"
>   #include "libcamera/internal/camera_controls.h"
> +#include "libcamera/internal/formats.h"
>   #include "libcamera/internal/pipeline_handler.h"
>   
>   /**
> @@ -314,6 +315,56 @@ std::size_t CameraConfiguration::size() const
>   	return config_.size();
>   }
>   
> +static bool isRaw(const PixelFormat &pixFmt)
> +{
> +	const PixelFormatInfo &info = PixelFormatInfo::info(pixFmt);
> +	return info.isValid() &&
> +	       info.colourEncoding == PixelFormatInfo::ColourEncodingRAW;
> +}
> +
> +CameraConfiguration::Status CameraConfiguration::validateColorSpaces(bool sharedColorSpace)
> +{
> +	Status status = Valid;
> +
> +	/* Find the largest non-raw stream (if any). */
> +	int index = -1;
> +	for (unsigned int i = 0; i < config_.size(); i++) {
> +		const StreamConfiguration &cfg = config_[i];
> +		if (!isRaw(cfg.pixelFormat) && (index < 0 || cfg.size > config_[i].size))
> +			index = i;
> +	}
> +
> +	/*
> +	 * Here we force raw streams to the correct color space. We handle
> +	 * the case where all output streams are to share a color space,
> +	 * which will match the color space of the largest (non-raw) stream.
> +	 */


I am questioning this policy, whether or not, let it best be left to 
specific platform instead? Or let me take a step back and ask how does 
one arrive at this policy or is it somewhat a convention?

> +	for (auto &cfg : config_) {
> +		std::optional<ColorSpace> initialColorSpace = cfg.colorSpace;
> +
> +		if (isRaw(cfg.pixelFormat))
> +			cfg.colorSpace = ColorSpace::Raw;
> +		else if (sharedColorSpace) {
> +			/*
> +			 * When all outputs share a color space, use the biggest
> +			 * output if that was set. If that was blank, but this
> +			 * stream's is not, then use this stream's color space for
> +			 * largest stream.
> +			 * (index must be != -1 if there are any non-raw streams.)
> +			 */
> +			if (config_[index].colorSpace)
> +				cfg.colorSpace = config_[index].colorSpace;
> +			else if (cfg.colorSpace)
> +				config_[index].colorSpace = cfg.colorSpace;
> +		}
> +
> +		if (cfg.colorSpace != initialColorSpace)
> +			status = Adjusted;
> +	}
> +
> +	return status;
> +}
> +
>   /**
>    * \var CameraConfiguration::transform
>    * \brief User-specified transform to be applied to the image