src/android/jpeg/encoder_libjpeg.cpp


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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2020, Google Inc.
 *
 * encoder_libjpeg.cpp - JPEG encoding using libjpeg native API
 */

#include "encoder_libjpeg.h"

#include <fcntl.h>
#include <iomanip>
#include <iostream>
#include <sstream>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
#include <vector>

#include <libcamera/camera.h>
#include <libcamera/formats.h>
#include <libcamera/pixel_format.h>

#include "libcamera/internal/formats.h"
#include "libcamera/internal/log.h"

using namespace libcamera;

LOG_DECLARE_CATEGORY(JPEG)

namespace {

struct JPEGPixelFormatInfo {
	J_COLOR_SPACE colorSpace;
	const PixelFormatInfo &pixelFormatInfo;
	bool nvSwap;
};

const std::map<PixelFormat, JPEGPixelFormatInfo> pixelInfo{
	{ formats::R8, { JCS_GRAYSCALE, PixelFormatInfo::info(formats::R8), false } },

	{ formats::RGB888, { JCS_EXT_BGR, PixelFormatInfo::info(formats::RGB888), false } },
	{ formats::BGR888, { JCS_EXT_RGB, PixelFormatInfo::info(formats::BGR888), false } },

	{ formats::NV12, { JCS_YCbCr, PixelFormatInfo::info(formats::NV12), false } },
	{ formats::NV21, { JCS_YCbCr, PixelFormatInfo::info(formats::NV21), true } },
	{ formats::NV16, { JCS_YCbCr, PixelFormatInfo::info(formats::NV16), false } },
	{ formats::NV61, { JCS_YCbCr, PixelFormatInfo::info(formats::NV61), true } },
	{ formats::NV24, { JCS_YCbCr, PixelFormatInfo::info(formats::NV24), false } },
	{ formats::NV42, { JCS_YCbCr, PixelFormatInfo::info(formats::NV42), true } },
};

const struct JPEGPixelFormatInfo &findPixelInfo(const PixelFormat &format)
{
	static const struct JPEGPixelFormatInfo invalidPixelFormat {
		JCS_UNKNOWN, PixelFormatInfo(), false
	};

	const auto iter = pixelInfo.find(format);
	if (iter == pixelInfo.end()) {
		LOG(JPEG, Error) << "Unsupported pixel format for JPEG encoder: "
				 << format.toString();
		return invalidPixelFormat;
	}

	return iter->second;
}

} /* namespace */

EncoderLibJpeg::EncoderLibJpeg()
{
	/* \todo Expand error handling coverage with a custom handler. */
	compress_.err = jpeg_std_error(&jerr_);

	jpeg_create_compress(&compress_);
}

EncoderLibJpeg::~EncoderLibJpeg()
{
	jpeg_destroy_compress(&compress_);
}

int EncoderLibJpeg::configure(const StreamConfiguration &cfg)
{
	const struct JPEGPixelFormatInfo info = findPixelInfo(cfg.pixelFormat);
	if (info.colorSpace == JCS_UNKNOWN)
		return -ENOTSUP;

	compress_.image_width = cfg.size.width;
	compress_.image_height = cfg.size.height;
	compress_.in_color_space = info.colorSpace;

	compress_.input_components = info.colorSpace == JCS_GRAYSCALE ? 1 : 3;

	jpeg_set_defaults(&compress_);

	pixelFormatInfo_ = &info.pixelFormatInfo;

	nv_ = pixelFormatInfo_->numPlanes() == 2;
	nvSwap_ = info.nvSwap;

	return 0;
}

void EncoderLibJpeg::compressRGB(Span<const uint8_t> frame)
{
	unsigned char *src = const_cast<unsigned char *>(frame.data());
	/* \todo Stride information should come from buffer configuration. */
	unsigned int stride = pixelFormatInfo_->stride(compress_.image_width, 0);

	JSAMPROW row_pointer[1];

	while (compress_.next_scanline < compress_.image_height) {
		row_pointer[0] = &src[compress_.next_scanline * stride];
		jpeg_write_scanlines(&compress_, row_pointer, 1);
	}
}

/*
 * Compress the incoming buffer from a supported NV format.
 * This naively unpacks the semi-planar NV12 to a YUV888 format for libjpeg.
 */
void EncoderLibJpeg::compressNV(Span<const uint8_t> frame)
{
	uint8_t tmprowbuf[compress_.image_width * 3];

	/*
	 * \todo Use the raw api, and only unpack the cb/cr samples to new line
	 * buffers. If possible, see if we can set appropriate pixel strides
	 * too to save even that copy.
	 *
	 * Possible hints at:
	 * https://sourceforge.net/p/libjpeg/mailman/message/30815123/
	 */
	unsigned int y_stride = pixelFormatInfo_->stride(compress_.image_width, 0);
	unsigned int c_stride = pixelFormatInfo_->stride(compress_.image_width, 1);

	unsigned int horzSubSample = 2 * compress_.image_width / c_stride;
	unsigned int vertSubSample = pixelFormatInfo_->planes[1].verticalSubSampling;

	unsigned int c_inc = horzSubSample == 1 ? 2 : 0;
	unsigned int cb_pos = nvSwap_ ? 1 : 0;
	unsigned int cr_pos = nvSwap_ ? 0 : 1;

	const unsigned char *src = frame.data();
	const unsigned char *src_c = src + y_stride * compress_.image_height;

	JSAMPROW row_pointer[1];
	row_pointer[0] = &tmprowbuf[0];

	for (unsigned int y = 0; y < compress_.image_height; y++) {
		unsigned char *dst = &tmprowbuf[0];

		const unsigned char *src_y = src + y * compress_.image_width;
		const unsigned char *src_cb = src_c + (y / vertSubSample) * c_stride + cb_pos;
		const unsigned char *src_cr = src_c + (y / vertSubSample) * c_stride + cr_pos;

		for (unsigned int x = 0; x < compress_.image_width; x += 2) {
			dst[0] = *src_y;
			dst[1] = *src_cb;
			dst[2] = *src_cr;
			src_y++;
			src_cb += c_inc;
			src_cr += c_inc;
			dst += 3;

			dst[0] = *src_y;
			dst[1] = *src_cb;
			dst[2] = *src_cr;
			src_y++;
			src_cb += 2;
			src_cr += 2;
			dst += 3;
		}

		jpeg_write_scanlines(&compress_, row_pointer, 1);
	}
}

int EncoderLibJpeg::encode(const FrameBuffer &source, Span<uint8_t> dest,
			   Span<const uint8_t> exifData, unsigned int quality)
{
	MappedFrameBuffer frame(&source, PROT_READ);
	if (!frame.isValid()) {
		LOG(JPEG, Error) << "Failed to map FrameBuffer : "
				 << strerror(frame.error());
		return frame.error();
	}