png_writer.cpp

#include "png_writer.h"
#include <stdlib.h>
#include <stdio.h>
#include <cstring>

#include <iostream>

//..................................................................................................
PngWriter::PngWriter(): width_(0), height_(0), row_pointers_(nullptr) {}

//..................................................................................................
PngWriter::~PngWriter() {
    if (row_pointers_ != nullptr) {
        free();
    }
}

//..................................................................................................
void PngWriter::free() {
    for (int32_t y = 0; y < height_; y++) {
        std::free(row_pointers_[y]);
    }
    std::free(row_pointers_);
    width_ = 0;
    height_ = 0;
}

//..................................................................................................
void PngWriter::allocate(int32_t width, int32_t height) {
    if (row_pointers_ != nullptr) {
        free();
    }
    width_ = width;
    height_ = height;
    row_pointers_ = (png_bytep*)malloc(sizeof(png_bytep) * height_);
    for (int y = 0; y < height_; y++) {
        row_pointers_[y] = (png_bytep)malloc(row_size());
    }
}

//..................................................................................................
void PngWriter::set_pixel(int32_t x, int32_t y, uint8_t value) {
    png_bytep row = row_pointers_[y];
    png_bytep px = &(row[x * 3]);
    px[0] = value;
    px[1] = value;
    px[2] = value;
}

//..................................................................................................
void PngWriter::set_all_pixels(uint8_t value) {
    for (int y = 0; y < height_; y++) {
        png_bytep row = row_pointers_[y];
        for (int x = 0; x < width_; x++) {
            png_bytep px = &(row[x * 3]);
            px[0] = value;
            px[1] = value;
            px[2] = value;
        }
    }
}

//..................................................................................................
void PngWriter::set_all_pixels_black() {
    for (int y = 0; y < height_; y++) {
        std::memset(row_pointers_[y], 0, row_size());
    }
}

//..................................................................................................
void PngWriter::write(char const* filename) {
    auto fp = fopen(filename, "wb");
    if (!fp) {
        std::cout << "Couldn't make file\n";
        abort();
    }

    png_structp png = png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
    if (!png) {
        std::cout << "Couldn't make png_structp\n";
        abort();
    }

    png_infop info = png_create_info_struct(png);
    if (!info) {
        std::cout << "Couldn't make png_structp\n";
        abort();
    }

    if (setjmp(png_jmpbuf(png))) {
        std::cout << "Couldn't set jump\n";
        abort();
    }

    png_init_io(png, fp);
    // Output is 8bit depth, RGB format.
    png_set_IHDR(png,
                 info,
                 width_,
                 height_,
                 8,
                 PNG_COLOR_TYPE_RGB,
                 PNG_INTERLACE_NONE,
                 PNG_COMPRESSION_TYPE_DEFAULT,
                 PNG_FILTER_TYPE_DEFAULT
    );
    png_write_info(png, info);

    if (png_get_rowbytes(png, info) != row_size()) {
        std::cout << "Allocated bad amount of memory\n";
        abort();
    }

    // To remove the alpha channel for PNG_COLOR_TYPE_RGB format,
    // Use png_set_filler().
    //png_set_filler(png_, 0, PNG_FILLER_AFTER);

    png_write_image(png, row_pointers_);
    png_write_end(png, NULL);

    if (png && info) {
        png_destroy_write_struct(&png, &info);
    }

    fclose(fp);
}