image_io_png.cpp

ncbi源码

        // store and validate our image's parameters
        size_t width  = 0;
        size_t height = 0;
        size_t depth  = 0;
        size_t x = -1;
        size_t y = -1;
        size_t w = -1;
        size_t h = -1;
        s_PngReadValidate(png_ptr, info_ptr,
                          width, height, depth,
                          x, y, w, h);

        // allocate our image and read, line by line
        image.Reset(new CImage(width, height, depth));
        unsigned char* row_ptr = image->SetData();
        for (size_t i = 0;  i < height;  ++i) {
            png_read_row(png_ptr, row_ptr, NULL);
            row_ptr += width * depth;
        }

        // read the end pointer
        png_read_end(png_ptr, end_ptr);

        // close and return
        s_PngReadFinalize(png_ptr, info_ptr, end_ptr);
    }
    catch (...) {
        // destroy everything
        s_PngReadFinalize(png_ptr, info_ptr, end_ptr);

        // rethrow
        throw;
    }

    return image.Release();
}


//
// ReadImage()
// read a PNG format image into memory, returning the image itself
// This version reads a subpart of an image
//
CImage* CImageIOPng::ReadImage(CNcbiIstream& istr,
                               size_t x, size_t y, size_t w, size_t h)
{
    png_structp png_ptr  = NULL;
    png_infop   info_ptr = NULL;
    png_infop   end_ptr  = NULL;
    CRef<CImage> image;

    try {
        // create our PNG structures
        s_PngReadInit(png_ptr, info_ptr, end_ptr);

        // begin reading our image
        png_set_read_fn(png_ptr, &istr, s_PngRead);
        png_read_info(png_ptr, info_ptr);

        // store and validate our image's parameters
        size_t width  = 0;
        size_t height = 0;
        size_t depth  = 0;
        s_PngReadValidate(png_ptr, info_ptr, width, height, depth,
                          x, y, w, h);

        // allocate our image
        image.Reset(new CImage(w, h, depth));
        unsigned char* to_data   = image->SetData();
        size_t         to_stride = image->GetWidth() * image->GetDepth();
        size_t         to_offs   = x * image->GetDepth();

        // allocate a scanline for this image
        vector<unsigned char> row(width * depth);
        unsigned char* row_ptr = &row[0];

        size_t i;

        // read up to our starting scan line
        for (i = 0;  i < y;  ++i) {
            png_read_row(png_ptr, row_ptr, NULL);
        }

        // read and convert the scanlines of interest
        for ( ;  i < y + h;  ++i) {
            png_read_row(png_ptr, row_ptr, NULL);
            memcpy(to_data, row_ptr + to_offs, to_stride);
            to_data += to_stride;
        }

        /**
        // read the rest of the image (do we need this?)
        for ( ;  i < height;  ++i) {
            png_read_row(png_ptr, row_ptr, NULL);
        }

        // read the end pointer
        png_read_end(png_ptr, end_ptr);
        **/

        // close and return
        s_PngReadFinalize(png_ptr, info_ptr, end_ptr);
    }
    catch (...) {
        // destroy everything
        s_PngReadFinalize(png_ptr, info_ptr, end_ptr);

        // rethrow
        throw;
    }

    return image.Release();
}


//
// WriteImage()
// write an image to a file in PNG format
// This version writes the entire image
//
void CImageIOPng::WriteImage(const CImage& image, CNcbiOstream& ostr,
                             CImageIO::ECompress compress)
{
    // make sure we've got an image
    if ( !image.GetData() ) {
        NCBI_THROW(CImageException, eWriteError,
                   "CImageIOPng::WriteImage(): "
                   "attempt to write an empty image");
    }

    // validate our image - we need RGB or RGBA images
    if (image.GetDepth() != 3  &&  image.GetDepth() != 4) {
        string msg("CImageIOPng::WriteImage(): invalid image depth: ");
        msg += NStr::IntToString(image.GetDepth());
        NCBI_THROW(CImageException, eWriteError, msg);
    }

    png_structp png_ptr  = NULL;
    png_infop   info_ptr = NULL;

    try {
        // initialize png stuff
        s_PngWriteInit(png_ptr, info_ptr, image, compress);

        // begin writing data
        png_set_write_fn(png_ptr, &ostr, s_PngWrite, s_PngFlush);
        png_write_info(png_ptr, info_ptr);

        // write our image, line-by-line
        unsigned char* row_ptr = const_cast<unsigned char*> (image.GetData());
        size_t width  = image.GetWidth();
        size_t height = image.GetHeight();
        size_t depth  = image.GetDepth();
        for (size_t i = 0;  i < height;  ++i) {
            png_write_row(png_ptr, row_ptr);
            row_ptr += width * depth;
        }

        // standard clean-up
        png_write_end(png_ptr, info_ptr);
        s_PngWriteFinalize(png_ptr, info_ptr);
    }
    catch (...) {
        s_PngWriteFinalize(png_ptr, info_ptr);
        throw;
    }
}


//
// WriteImage()
// write an image to a file in PNG format
// This version writes only a subpart of the image
//
void CImageIOPng::WriteImage(const CImage& image, CNcbiOstream& ostr,
                             size_t x, size_t y, size_t w, size_t h,
                             CImageIO::ECompress compress)
{
    // make sure we've got an image
    if ( !image.GetData() ) {
        NCBI_THROW(CImageException, eWriteError,
                   "CImageIOPng::WriteImage(): "
                   "attempt to write an empty image");
    }

    // validate our image - we need RGB or RGBA images
    if (image.GetDepth() != 3  &&  image.GetDepth() != 4) {
        string msg("CImageIOPng::WriteImage(): invalid image depth: ");
        msg += NStr::IntToString(image.GetDepth());
        NCBI_THROW(CImageException, eWriteError, msg);
    }

    png_structp png_ptr  = NULL;
    png_infop   info_ptr = NULL;

    try {
        // initialize png stuff
        s_PngWriteInit(png_ptr, info_ptr, image, compress);

        // begin writing data
        png_set_write_fn(png_ptr, &ostr, s_PngWrite, s_PngFlush);
        png_write_info(png_ptr, info_ptr);

        // write our image
        // we plan to march through only part of our image
        // get a pointer to the start of our scan line
        //
        // NB: the const cast is necessary as png_write_row takes a non-const
        // pointer (go figure...)
        unsigned char* from_data = const_cast<unsigned char*>(image.GetData());
        from_data += (y * image.GetWidth() + x) * image.GetDepth();
        size_t from_stride = image.GetWidth() * image.GetDepth();

        // march out h scan lines
        for (size_t i = 0;  i < h;  ++i) {
            png_write_row(png_ptr, from_data);
            from_data += from_stride;
        }


        // standard clean-up
        png_write_end(png_ptr, info_ptr);
        s_PngWriteFinalize(png_ptr, info_ptr);
    }
    catch (...) {
        s_PngWriteFinalize(png_ptr, info_ptr);
        throw;
    }
}


END_NCBI_SCOPE

#else // !HAVE_LIBPNG

//
// LIBPNG functionality not included - we stub out the various needed
// functions
//


BEGIN_NCBI_SCOPE


CImage* CImageIOPng::ReadImage(CNcbiIstream& file)
{
    NCBI_THROW(CImageException, eUnsupported,
               "CImageIOPng::ReadImage(): PNG format not supported");
}


CImage* CImageIOPng::ReadImage(CNcbiIstream& file,
                               size_t, size_t, size_t, size_t)
{
    NCBI_THROW(CImageException, eUnsupported,
               "CImageIOPng::ReadImage(): PNG format not supported");
}


void CImageIOPng::WriteImage(const CImage& image, CNcbiOstream& file,
                             CImageIO::ECompress)
{
    NCBI_THROW(CImageException, eUnsupported,
               "CImageIOPng::WriteImage(): PNG format not supported");
}


void CImageIOPng::WriteImage(const CImage& image, CNcbiOstream& file,
                             size_t, size_t, size_t, size_t,
                             CImageIO::ECompress)
{
    NCBI_THROW(CImageException, eUnsupported,
               "CImageIOPng::WriteImage(): PNG format not supported");
}


END_NCBI_SCOPE


#endif  // HAVE_LIBPNG

/*
 * ===========================================================================
 * $Log: image_io_png.cpp,v $
 * Revision 1000.3  2004/06/01 19:41:37  gouriano
 * PRODUCTION: UPGRADED [GCC34_MSVC7] Dev-tree R1.5
 *
 * Revision 1.5  2004/05/17 21:07:58  gorelenk
 * Added include of PCH ncbi_pch.hpp
 *
 * Revision 1.4  2003/12/20 17:50:53  dicuccio
 * Fixed bugs in reading of subimage - don't declare image in try block; use
 * correct height.  Dropped unnecessary finalization - don't need to scan whole
 * image.
 *
 * Revision 1.3  2003/12/16 15:49:37  dicuccio
 * Large re-write of image handling.  Added improved error-handling and support
 * for streams-based i/o (via hooks into each client library).
 *
 * Revision 1.2  2003/11/03 15:19:57  dicuccio
 * Added optional compression parameter
 *
 * Revision 1.1  2003/06/03 15:17:13  dicuccio
 * Initial revision of image library
 *
 * ===========================================================================
 */