[libcamera-devel] [PATCH v2 2/3] android: jpeg: Introduce a simple image thumbnailer

[Kieran Bingham]

Hi Umang,

On 27/10/2020 21:24, Umang Jain wrote:
> Add a basic image Thumbnailer class for the frames being captured.
> Currently, the thumbnailer can scale NV12 frames. It shall be used
> to generate a thumbnail image for EXIF metadata, in the subsequent
> commit.
> 
> Signed-off-by: Umang Jain <email at uajain.com>
> ---
>  src/android/jpeg/thumbnailer.cpp | 113 +++++++++++++++++++++++++++++++
>  src/android/jpeg/thumbnailer.h   |  36 ++++++++++
>  src/android/meson.build          |   1 +
>  3 files changed, 150 insertions(+)
>  create mode 100644 src/android/jpeg/thumbnailer.cpp
>  create mode 100644 src/android/jpeg/thumbnailer.h
> 
> diff --git a/src/android/jpeg/thumbnailer.cpp b/src/android/jpeg/thumbnailer.cpp
> new file mode 100644
> index 0000000..2e3c478
> --- /dev/null
> +++ b/src/android/jpeg/thumbnailer.cpp
> @@ -0,0 +1,113 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2020, Google Inc.
> + *
> + * thumbnailer.cpp - Simple image thumbnailer
> + */
> +
> +#include "thumbnailer.h"
> +
> +#include <libcamera/formats.h>
> +
> +#include "libcamera/internal/log.h"
> +
> +using namespace libcamera;
> +
> +LOG_DEFINE_CATEGORY(Thumbnailer)
> +
> +Thumbnailer::Thumbnailer()
> +	: valid_(false)
> +{
> +}
> +
> +void Thumbnailer::configure(const Size &sourceSize, PixelFormat pixelFormat)
> +{
> +	sourceSize_ = sourceSize;
> +	pixelFormat_ = pixelFormat;
> +
> +	if (pixelFormat_ != formats::NV12) {
> +		LOG (Thumbnailer, Error)
> +			<< "Failed to configure: Pixel Format "
> +			<< pixelFormat_.toString() << " unsupported.";
> +		return;
> +	}
> +
> +	targetSize_ = computeThumbnailSize();
> +
> +	valid_ = true;
> +}
> +
> +/*
> + * The Exif specification recommends the width of the thumbnail to be a
> + * multiple of 16 (section 4.8.1). Hence, compute the corresponding height
> + * keeping the aspect ratio same as of the source.
> + */
> +Size Thumbnailer::computeThumbnailSize() const
> +{
> +	unsigned int targetHeight;
> +	constexpr unsigned int kTargetWidth = 160;
> +
> +	targetHeight = kTargetWidth * sourceSize_.height / sourceSize_.width;
> +
> +	if (targetHeight & 1)
> +		targetHeight++;
> +
> +	return Size(kTargetWidth, targetHeight);
> +}
> +
> +void
> +Thumbnailer::createThumbnail(const FrameBuffer &source,
> +			     std::vector<unsigned char> *destination)

Checkstyle complains here.

Seems your githook was disabled, but fixed now ;-)

I'll fix up these small style warnings locally, as I think these patches
are ready to push. Just testing and we'll see.


> +{
> +	MappedFrameBuffer frame(&source, PROT_READ);
> +	if (!frame.isValid()) {
> +		LOG(Thumbnailer, Error)
> +			<< "Failed to map FrameBuffer : "
> +			<< strerror(frame.error());
> +		return;
> +	}
> +
> +	if (!valid_) {
> +		LOG(Thumbnailer, Error) << "Config is unconfigured or invalid.";
> +		return;
> +	}
> +
> +	const unsigned int sw = sourceSize_.width;
> +	const unsigned int sh = sourceSize_.height;
> +	const unsigned int tw = targetSize_.width;
> +	const unsigned int th = targetSize_.height;
> +
> +	ASSERT(tw % 2 == 0 && th % 2 == 0);
> +
> +	/* Image scaling block implementing nearest-neighbour algorithm. */
> +	unsigned char *src = static_cast<unsigned char *>(frame.maps()[0].data());
> +	unsigned char *srcC = src + sh * sw;
> +	unsigned char *srcCb, *srcCr;
> +	unsigned char *dstY, *srcY;
> +
> +	size_t dstSize = (th * tw) + ((th / 2) * tw);
> +	destination->resize(dstSize);
> +	unsigned char *dst = destination->data();
> +	unsigned char *dstC = dst + th * tw;
> +
> +	for (unsigned int y = 0; y < th; y += 2) {
> +		unsigned int sourceY = (sh * y + th / 2) / th;
> +
> +		dstY = dst + y * tw;
> +		srcY = src + sw * sourceY;
> +		srcCb = srcC + (sourceY / 2) * sw + 0;
> +		srcCr = srcC + (sourceY / 2) * sw + 1;
> +
> +		for (unsigned int x = 0; x < tw; x += 2) {
> +			unsigned int sourceX = (sw * x + tw / 2) / tw;
> +
> +			dstY[x] = srcY[sourceX];
> +			dstY[tw + x] = srcY[sw + sourceX];
> +			dstY[x + 1] = srcY[sourceX + 1];
> +			dstY[tw + x + 1] = srcY[sw + sourceX + 1];
> +
> +			dstC[(y / 2) * tw + x + 0] = srcCb[(sourceX / 2) * 2];
> +			dstC[(y / 2) * tw + x + 1] = srcCr[(sourceX / 2) * 2];
> +		}
> +	}
> +}
> diff --git a/src/android/jpeg/thumbnailer.h b/src/android/jpeg/thumbnailer.h
> new file mode 100644
> index 0000000..16e6951
> --- /dev/null
> +++ b/src/android/jpeg/thumbnailer.h
> @@ -0,0 +1,36 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2020, Google Inc.
> + *
> + * thumbnailer.h - Simple image thumbnailer
> + */
> +#ifndef __ANDROID_JPEG_THUMBNAILER_H__
> +#define __ANDROID_JPEG_THUMBNAILER_H__
> +
> +#include <libcamera/geometry.h>
> +
> +#include "libcamera/internal/buffer.h"
> +#include "libcamera/internal/formats.h"
> +
> +class Thumbnailer
> +{
> +public:
> +	Thumbnailer();
> +
> +	void configure(const libcamera::Size &sourceSize,
> +		       libcamera::PixelFormat pixelFormat);
> +	void createThumbnail(const libcamera::FrameBuffer &source,
> +			     std::vector<unsigned char> *dest);
> +	const libcamera::Size& size() const { return targetSize_; }

Also
/Size& size/Size &size/

But I'll fix.

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>


> +
> +private:
> +	libcamera::Size computeThumbnailSize() const;
> +
> +	libcamera::PixelFormat pixelFormat_;
> +	libcamera::Size sourceSize_;
> +	libcamera::Size targetSize_;
> +
> +	bool valid_;
> +};
> +
> +#endif /* __ANDROID_JPEG_THUMBNAILER_H__ */
> diff --git a/src/android/meson.build b/src/android/meson.build
> index f72376a..3d4d3be 100644
> --- a/src/android/meson.build
> +++ b/src/android/meson.build
> @@ -25,6 +25,7 @@ android_hal_sources = files([
>      'jpeg/encoder_libjpeg.cpp',
>      'jpeg/exif.cpp',
>      'jpeg/post_processor_jpeg.cpp',
> +    'jpeg/thumbnailer.cpp',
>  ])
>  
>  android_camera_metadata_sources = files([
> 

-- 
Regards
--
Kieran