mozaic/lib/image_io.cpp

#include "image_io.hpp"
#include "utilities.hpp"

#include <av/sws.hpp>

extern "C" {
#include <libavutil/frame.h>
#include <libavutil/mem.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
}

#include <algorithm>
#include <cassert>
#include <fstream>
#include <iostream>
#include <stdexcept>


raw_rgb_image::raw_rgb_image()
: data()
, frame(nullptr, [](auto x){ av_frame_free(&x); })
{}

raw_rgb_image::raw_rgb_image(int W, int H)
: data(make_u(avpicture_get_size(AV_PIX_FMT_RGB24, W, H)))
, frame(av::frame_alloc())
{
	avpicture_fill(reinterpret_cast<AVPicture*>(frame.get()), data.data(), AV_PIX_FMT_RGB24, W, H);
	frame->width = W;
	frame->height = H;
	frame->format = AV_PIX_FMT_RGB24;
}

int raw_rgb_image::width() const { return frame->width; }
int raw_rgb_image::height() const { return frame->height; }
AVPixelFormat raw_rgb_image::format() const { return av::get_format(frame); }


av::frame open_image(std::string const & filename){
	// Open the file
	auto format_context = av::format_open_input(filename, nullptr, nullptr);

	// Get the codec and let us own the buffers
	auto codec_context = av::context_from_stream(format_context, 0);
	const auto codec = avcodec_find_decoder(codec_context->codec_id);
	codec_context->refcounted_frames = 1;

	// Open the codec
	const auto opened_codec = av::codec_open(codec_context, codec, nullptr);

	// Allocate frame
	av::frame frame = av::frame_alloc();

	// things to read and decode it
	av::packet_buffer empty_packet;
	int finished = 0;
	while(auto packet = av::read_frame(format_context, empty_packet)) {
		if(packet->stream_index != 0) continue;

		int ret = avcodec_decode_video2(codec_context.get(), frame.get(), &finished, packet.get());
		if (ret <= 0) {
			printf("Error [%d] while decoding frame: %s\n", ret, strerror(AVERROR(ret)));
			throw std::runtime_error("boem packet");
		}

		// we only need the first frame
		if(finished) break;
	}

	// some decoders need extra passes
	while(!finished) {
		avcodec_decode_video2(codec_context.get(), frame.get(), &finished, &empty_packet);
	}

	return frame;
}


void crop_to_square(av::frame& frame){
	int diff = frame->width - frame->height;
	if(diff > 0) {
		av::crop(frame, diff/2, 0, frame->height, frame->height);
	} else if(diff < 0) {
		av::crop(frame, 0, -diff/2, frame->width, frame->width);
	}
}

av::frame crop_to_square(const av::frame& frame){
	return crop_to_square(av::frame_clone(frame));
}

av::frame crop_to_square(av::frame && frame){
	crop_to_square(frame);
	return std::move(frame);
}

raw_rgb_image to_raw_rgb_image(av::frame const & frame, int new_width, int new_height){
	raw_rgb_image image(new_width, new_height);

	auto context = sws::create_context(frame, image.frame);
	sws::scale(context, frame, image.frame);

	return image;
}


void apply_to_tiles(std::string const & filename, int h_tiles, int v_tiles, std::function<void(int, int, av::frame const &)> fun) {
	const auto org_frame = open_image(filename);

	// create raw buffer for the callback
	// TODO: do not scale the cropped region
	raw_rgb_image image(512, 512);

	// create the tiles
	const int width = org_frame->width / h_tiles;
	const int height = org_frame->height / v_tiles;
	for(int r = 0; r < v_tiles; ++r){
		for(int c = 0; c < h_tiles; ++c){
			const int x_crop = c * width;
			const int y_crop = r * height;

			const auto cropped_frame = av::crop(org_frame, x_crop, y_crop, width, height);
			auto context = sws::create_context(cropped_frame, image.frame);
			sws::scale(context, cropped_frame, image.frame);
			fun(c, r, image.frame);
		}
	}
}

void save_as_jpg(av::frame const & frame, std::string const & filename){
	const auto pix_fmt = AV_PIX_FMT_YUVJ444P;

	std::vector<uint8_t, av::allocator<uint8_t>> data(make_u(avpicture_get_size(pix_fmt, frame->width,
	frame->height)), 0);
	av::frame converted_frame = av::frame_alloc();
	avpicture_fill(reinterpret_cast<AVPicture*>(converted_frame.get()), data.data(), pix_fmt, frame->width, frame->height);
	converted_frame->width = frame->width;
	converted_frame->height = frame->height;
	converted_frame->format = pix_fmt;

	{
		auto sws_context = sws::create_context(frame, converted_frame);
		sws::scale(sws_context, frame, converted_frame);
	}

	encode_as_jpg(converted_frame, filename);
}

void encode_as_jpg(const av::frame& frame, const std::string& filename){
	auto const codec_id= AV_CODEC_ID_MJPEG;
	const auto pix_fmt = av::get_format(frame);
	const auto codec = av::find_encoder(codec_id);

	auto codec_ctx = av::context_alloc(codec);
	codec_ctx->pix_fmt = pix_fmt;
	codec_ctx->width = frame->width;
	codec_ctx->height = frame->height;
	codec_ctx->time_base = av_make_q(1, 1);

	const auto opened_codec = av::codec_open(codec_ctx, codec, nullptr);

	const auto buffer_size = avpicture_get_size(pix_fmt, codec_ctx->width, codec_ctx->height);
	std::vector<uint8_t> buffer(make_u(buffer_size), 0);
	const auto output_size = avcodec_encode_video(codec_ctx.get(), buffer.data(), buffer_size, frame.get());
	assert(output_size <= buffer_size);

	std::ofstream file(filename);
	file.write(reinterpret_cast<char*>(buffer.data()), output_size);
}