portapack-mayhem/firmware/common/png_writer.cpp

/*
 * Copyright (C) 2016 Jared Boone, ShareBrained Technology, Inc.
 *
 * This file is part of PortaPack.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#include "png_writer.hpp"

static constexpr std::array<uint8_t, 8> png_file_header{{
    0x89,
    0x50,
    0x4e,
    0x47,
    0x0d,
    0x0a,
    0x1a,
    0x0a,
}};

static constexpr std::array<uint8_t, 25> png_ihdr_screen_capture{{
    0x00, 0x00, 0x00, 0x0d,  // IHDR length
    0x49, 0x48, 0x44, 0x52,  // IHDR type
    0x00, 0x00, 0x00, 0xf0,  // width = 240
    0x00, 0x00, 0x01, 0x40,  // height = 320
    0x08,                    // bit_depth = 8
    0x02,                    // color_type = 2
    0x00,                    // compression_method = 0
    0x00,                    // filter_method = 0
    0x00,                    // interlace_method = 0
    0x0d, 0x8a, 0x66, 0x04,  // CRC
}};

static constexpr std::array<uint8_t, 4> png_idat_chunk_type{{
    0x49, 0x44, 0x41, 0x54,  // IDAT type
}};

static constexpr std::array<uint8_t, 12> png_iend{{
    0x00, 0x00, 0x00, 0x00,  // IEND length
    0x49, 0x45, 0x4e, 0x44,  // IEND type
    0xae, 0x42, 0x60, 0x82,  // CRC
}};

Optional<File::Error> PNGWriter::create(
    const std::filesystem::path& filename) {
    const auto create_error = file.create(filename);
    if (create_error.is_valid()) {
        return create_error;
    }

    file.write(png_file_header);
    file.write(png_ihdr_screen_capture);

    write_chunk_header(
        2 + height * (5 + 1 + width * 3) + 4,
        png_idat_chunk_type);

    constexpr std::array<uint8_t, 2> zlib_header{0x78, 0x01};  // Zlib CM, CINFO, FLG.
    write_chunk_content(zlib_header);

    return {};
}

PNGWriter::~PNGWriter() {
    write_chunk_content(adler_32.bytes());
    write_chunk_crc();

    file.write(png_iend);
}

void PNGWriter::write_scanline(const std::array<ui::ColorRGB888, 240>& scanline) {
    constexpr uint8_t scanline_filter_type = 0;
    constexpr uint32_t deflate_block_length = 1 + sizeof(scanline);

    const std::array<uint8_t, 6> deflate_and_scanline_header{
        static_cast<uint8_t>((scanline_count == (height - 1)) ? 0x01 : 0x00),  // DEFLATE header bits, bfinal=0, btype=00
        static_cast<uint8_t>((deflate_block_length >> 0) & 0xff),              // Length LSB
        static_cast<uint8_t>((deflate_block_length >> 8) & 0xff),              // Length MSB
        static_cast<uint8_t>((deflate_block_length >> 0) & 0xff) ^ 0xff,       // ~Length LSB
        static_cast<uint8_t>((deflate_block_length >> 8) & 0xff) ^ 0xff,       // ~Length MSB
        scanline_filter_type,
    };
    write_chunk_content(deflate_and_scanline_header);

    adler_32.feed(scanline_filter_type);
    adler_32.feed(scanline);

    // Small writes to avoid some sort of large-transfer plus block
    // boundary FatFs or SDC driver bug?
    write_chunk_content(&scanline[0], 80 * sizeof(ui::ColorRGB888));
    write_chunk_content(&scanline[80], 80 * sizeof(ui::ColorRGB888));
    write_chunk_content(&scanline[160], 80 * sizeof(ui::ColorRGB888));

    scanline_count++;
}

void PNGWriter::write_chunk_header(
    const size_t length,
    const std::array<uint8_t, 4>& type) {
    write_uint32_be(length);
    crc.reset();
    write_chunk_content(type);
}

void PNGWriter::write_chunk_content(const void* const p, const size_t count) {
    file.write(p, count);
    crc.process_bytes(p, count);
}

void PNGWriter::write_chunk_crc() {
    write_uint32_be(crc.checksum());
}

void PNGWriter::write_uint32_be(const uint32_t v) {
    file.write(std::array<uint8_t, 4>{{
        static_cast<uint8_t>((v >> 24) & 0xff),
        static_cast<uint8_t>((v >> 16) & 0xff),
        static_cast<uint8_t>((v >> 8) & 0xff),
        static_cast<uint8_t>((v >> 0) & 0xff),
    }});
}