src/pnm.imageio/pnmoutput.cpp

// Copyright 2008-present Contributors to the OpenImageIO project.
// SPDX-License-Identifier: BSD-3-Clause
// https://github.com/OpenImageIO/oiio/blob/master/LICENSE.md

#include <fstream>

#include <OpenImageIO/filesystem.h>
#include <OpenImageIO/imageio.h>

OIIO_PLUGIN_NAMESPACE_BEGIN


class PNMOutput final : public ImageOutput {
public:
    virtual ~PNMOutput();
    virtual const char* format_name(void) const override { return "pnm"; }
    virtual bool open(const std::string& name, const ImageSpec& spec,
                      OpenMode mode = Create) override;
    virtual bool close() override;
    virtual bool write_scanline(int y, int z, TypeDesc format, const void* data,
                                stride_t xstride) override;
    virtual bool write_tile(int x, int y, int z, TypeDesc format,
                            const void* data, stride_t xstride,
                            stride_t ystride, stride_t zstride) override;

private:
    std::string m_filename;  ///< Stash the filename
    OIIO::ofstream m_file;
    unsigned int m_max_val, m_pnm_type;
    unsigned int m_dither;
    std::vector<unsigned char> m_scratch;
    std::vector<unsigned char> m_tilebuffer;
};


// Obligatory material to make this a recognizeable imageio plugin:
OIIO_PLUGIN_EXPORTS_BEGIN

OIIO_EXPORT ImageOutput*
pnm_output_imageio_create()
{
    return new PNMOutput;
}

OIIO_EXPORT const char* pnm_output_extensions[] = { "ppm", "pgm", "pbm", "pnm",
                                                    nullptr };

OIIO_PLUGIN_EXPORTS_END


inline void
write_ascii_binary(std::ostream& file, const unsigned char* data,
                   const stride_t stride, const ImageSpec& spec)
{
    for (int x = 0; x < spec.width; x++)
        file << (data[x * stride] ? '1' : '0') << "\n";
}


inline void
write_raw_binary(std::ostream& file, const unsigned char* data,
                 const stride_t stride, const ImageSpec& spec)
{
    unsigned char val;
    for (int x = 0; x < spec.width;) {
        val = 0;
        for (int bit = 7; bit >= 0 && x < spec.width; x++, bit--)
            val += (data[x * stride] ? (1 << bit) : 0);
        file.write((char*)&val, sizeof(char));
    }
}


template<class T>
inline void
write_ascii(std::ostream& file, const T* data, const stride_t stride,
            const ImageSpec& spec, unsigned int max_val)
{
    unsigned int pixel, val;
    for (int x = 0; x < spec.width; x++) {
        pixel = x * stride;
        for (int c = 0; c < spec.nchannels; c++) {
            val = data[pixel + c];
            val = val * max_val / std::numeric_limits<T>::max();
            file << val << "\n";
        }
    }
}


template<class T>
inline void
write_raw(std::ostream& file, const T* data, const stride_t stride,
          const ImageSpec& spec, unsigned int max_val)
{
    unsigned char byte;
    unsigned int pixel, val;
    for (int x = 0; x < spec.width; x++) {
        pixel = x * stride;
        for (int c = 0; c < spec.nchannels; c++) {
            val = data[pixel + c];
            val = val * max_val / std::numeric_limits<T>::max();
            if (sizeof(T) == 2) {
                // Writing a 16bit ppm file
                // I'll adopt the practice of Netpbm and write the MSB first
                byte = static_cast<unsigned char>(val >> 8);
                file.write((char*)&byte, 1);
                byte = static_cast<unsigned char>(val & 0xff);
                file.write((char*)&byte, 1);
            } else {
                // This must be an 8bit ppm file
                byte = static_cast<unsigned char>(val);
                file.write((char*)&byte, 1);
            }
        }
    }
}


PNMOutput::~PNMOutput() { close(); }


bool
PNMOutput::open(const std::string& name, const ImageSpec& userspec,
                OpenMode mode)
{
    if (mode != Create) {
        errorf("%s does not support subimages or MIP levels", format_name());
        return false;
    }

    close();                             // Close any already-opened file
    m_spec = userspec;                   // Stash the spec
    m_spec.set_format(TypeDesc::UINT8);  // Force 8 bit output
    int bits_per_sample = m_spec.get_int_attribute("oiio:BitsPerSample", 8);
    m_dither            = (m_spec.format == TypeDesc::UINT8)
                              ? m_spec.get_int_attribute("oiio:dither", 0)
                              : 0;

    if (m_spec.nchannels != 1 && m_spec.nchannels != 3) {
        errorf("%s does not support %d-channel images\n", format_name(),
               m_spec.nchannels);
        return false;
    }

    if (bits_per_sample == 1)
        m_pnm_type = 4;
    else if (m_spec.nchannels == 1)
        m_pnm_type = 5;
    else
        m_pnm_type = 6;
    if (!m_spec.get_int_attribute("pnm:binary", 1)) {
        m_pnm_type -= 3;
        Filesystem::open(m_file, name);

    } else {
        Filesystem::open(m_file, name, std::ios::out | std::ios::binary);
    }

    if (!m_file) {
        errorf("Could not open \"%s\"", name);
        return false;
    }

    m_max_val = (1 << bits_per_sample) - 1;
    // Write header
    m_file << "P" << m_pnm_type << std::endl;
    m_file << m_spec.width << " " << m_spec.height << std::endl;
    if (m_pnm_type != 1 && m_pnm_type != 4)  // only non-monochrome
        m_file << m_max_val << std::endl;

    // If user asked for tiles -- which this format doesn't support, emulate
    // it by buffering the whole image.
    if (m_spec.tile_width && m_spec.tile_height)
        m_tilebuffer.resize(m_spec.image_bytes());

    return m_file.good();
}


bool
PNMOutput::close()
{
    if (!m_file) {  // already closed
        return true;
    }

    bool ok = true;
    if (m_spec.tile_width) {
        // Handle tile emulation -- output the buffered pixels
        OIIO_DASSERT(m_tilebuffer.size());
        ok &= write_scanlines(m_spec.y, m_spec.y + m_spec.height, 0,
                              m_spec.format, &m_tilebuffer[0]);
        std::vector<unsigned char>().swap(m_tilebuffer);
    }

    m_file.close();
    return true;
}


bool
PNMOutput::write_scanline(int y, int z, TypeDesc format, const void* data,
                          stride_t xstride)
{
    if (!m_file)
        return false;
    if (z)
        return false;

    m_spec.auto_stride(xstride, format, spec().nchannels);
    const void* origdata = data;
    data = to_native_scanline(format, data, xstride, m_scratch, m_dither, y, z);
    if (data != origdata)  // a conversion happened...
        xstride = spec().nchannels;

    switch (m_pnm_type) {
    case 1:
        write_ascii_binary(m_file, (unsigned char*)data, xstride, m_spec);
        break;
    case 2:
    case 3:
        if (m_max_val > std::numeric_limits<unsigned char>::max())
            write_ascii(m_file, (unsigned short*)data, xstride, m_spec,
                        m_max_val);
        else
            write_ascii(m_file, (unsigned char*)data, xstride, m_spec,
                        m_max_val);
        break;
    case 4:
        write_raw_binary(m_file, (unsigned char*)data, xstride, m_spec);
        break;
    case 5:
    case 6:
        if (m_max_val > std::numeric_limits<unsigned char>::max())
            write_raw(m_file, (unsigned short*)data, xstride, m_spec,
                      m_max_val);
        else
            write_raw(m_file, (unsigned char*)data, xstride, m_spec, m_max_val);
        break;
    default: return false;
    }

    return m_file.good();
}


bool
PNMOutput::write_tile(int x, int y, int z, TypeDesc format, const void* data,
                      stride_t xstride, stride_t ystride, stride_t zstride)
{
    // Emulate tiles by buffering the whole image
    return copy_tile_to_image_buffer(x, y, z, format, data, xstride, ystride,
                                     zstride, &m_tilebuffer[0]);
}


OIIO_PLUGIN_NAMESPACE_END