bmpwriter.cc

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#include "base/bmpwriter.hh"

#include <cassert>

#include "base/logging.hh"

const char* BmpWriter::_imgExtension = "bmp";

// bitmap class ctor
BmpWriter::BmpWriter(const FrameBuffer *_fb)
    : ImgWriter(_fb)
{
}

const BmpWriter::CompleteV1Header
BmpWriter::getCompleteHeader() const
{
    const uint32_t pixel_array_size(sizeof(PixelType) * fb.area());
    const uint32_t file_size(sizeof(CompleteV1Header) + pixel_array_size);

    const CompleteV1Header header = {
        // File header
        {
            {'B','M'}, /* Magic */
            file_size,
            0, 0, /* Reserved */
            sizeof(CompleteV1Header) /* Offset to pixel array */
        },
        // Info/DIB header
        {
            sizeof(InfoHeaderV1),
            fb.width(),
            fb.height(),
            1, /* Color planes */
            32, /* Bits per pixel */
            0, /* No compression */
            pixel_array_size, /* Image size in bytes */
            2835, /* x pixels per meter (assume 72 DPI) */
            2835, /* y pixels per meter (assume 72 DPI) */
            0, /* Colors in color table */
            0 /* Important color count (0 == all are important) */
        }
    };

    return header;
}

void
BmpWriter::write(std::ostream &bmp) const
{
    const CompleteV1Header header(getCompleteHeader());

    // 1.  write the header
    bmp.write(reinterpret_cast<const char *>(&header), sizeof(header));

    // 2.  write the bitmap data
    // BMP start store data left to right starting with the bottom row
    // so we need to do some creative flipping
    std::vector<PixelType> line_buffer(fb.width());
    for (int y = 0; y < fb.height(); ++y) {
        for (unsigned x = 0; x < fb.width(); ++x)
            line_buffer[x] = fb.pixel(x, fb.height() - y - 1);

        bmp.write(reinterpret_cast<const char *>(line_buffer.data()),
                  line_buffer.size() * sizeof(line_buffer[0]));
    }

    bmp.flush();
}