png.hpp

// Copyright Take Vos 2020-2021.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 
 
#pragma once
 
#include "../required.hpp"
#include "../pixel_map.hpp"
#include "../color/sfloat_rgba16.hpp"
#include "../geometry/identity.hpp"
#include "../numeric_array.hpp"
#include "../URL.hpp"
#include "../resource_view.hpp"
#include "../byte_string.hpp"
#include <span>
#include <vector>
#include <cstddef>
#include <cstdint>
 
namespace tt {
 
class png {
public:
    png(std::span<std::byte const> bytes);
 
    png(std::unique_ptr<resource_view> view);
 
    png(URL const &url) :
        png(url.loadView()) {}
 
    i32x4 extent() const noexcept {
        return i32x4{width, height};
    }
 
    void decode_image(pixel_map<sfloat_rgba16> &image) const;
 
    static pixel_map<sfloat_rgba16> load(URL const &url);
 
private:
    matrix3 color_to_sRGB = geo::identity();
 
    std::vector<float> transfer_function;
 
    int width = 0;
    int height = 0;
    int bit_depth = 0;
    int color_type = 0;
    int compression_method = 0;
    int filter_method = 0;
    int interlace_method = 0;
 
    bool has_alpha;
    bool is_palletted;
    bool is_color;
    int samples_per_pixel = 0;
    int bits_per_pixel = 0;
    int bytes_per_pixel = 0;
    int bytes_per_line = 0;
    int stride = 0;
 
    std::vector<std::span<std::byte const>> idat_chunk_data;
 
    std::unique_ptr<resource_view> view;
 
    void read_header(std::span<std::byte const> bytes, ssize_t &offset);
    void read_chunks(std::span<std::byte const> bytes, ssize_t &offset);
    void read_IHDR(std::span<std::byte const> bytes);
    void read_cHRM(std::span<std::byte const> bytes);
    void read_gAMA(std::span<std::byte const> bytes);
    void read_iBIT(std::span<std::byte const> bytes);
    void read_iCCP(std::span<std::byte const> bytes);
    void read_sRGB(std::span<std::byte const> bytes);
    void generate_sRGB_transfer_function() noexcept;
    void generate_Rec2100_transfer_function() noexcept;
    void generate_gamma_transfer_function(float gamma) noexcept;
    bstring decompress_IDATs(ssize_t image_data_size) const;
    void unfilter_lines(bstring &image_data) const;
    void unfilter_line(std::span<uint8_t> line, std::span<uint8_t const> prev_line) const;
    void unfilter_line_sub(std::span<uint8_t> line, std::span<uint8_t const> prev_line) const noexcept;
    void unfilter_line_up(std::span<uint8_t> line, std::span<uint8_t const> prev_line) const noexcept;
    void unfilter_line_average(std::span<uint8_t> line, std::span<uint8_t const> prev_line) const noexcept;
    void unfilter_line_paeth(std::span<uint8_t> line, std::span<uint8_t const> prev_line) const noexcept;
    void data_to_image(bstring bytes, pixel_map<sfloat_rgba16> &image) const noexcept;
    void data_to_image_line(std::span<std::byte const> bytes, pixel_row<sfloat_rgba16> &row) const noexcept;
    i32x4 extract_pixel_from_line(std::span<std::byte const> bytes, int x) const noexcept;
 
};
 
}