On Sun, Mar 29, 2009 at 9:10 PM, Kenny Riddile <kfriddile@yahoo.com> wrote:

Kenny Riddile wrote:

...

I'm still pretty inexperienced with the iostreams library, so this may be a simple question.  I'm trying to use GIL to write a PNG to a memory stream instead of a file stream.  The write_view() function in the new version of GIL's io extension expects an ostream opened in binary mode as it's first parameter, such as:

using namespace std; using namespace boost::gil;

ofstream outputStream( "foo.png", ios::out | ios::binary ); write_view( outputStream, const_view(image), png_tag() );

I'm attempting to write to memory instead of a file, by doing this:

using namespace boost::gil; using namespace boost::iostreams;

typedef stream< back_insert_device< std::vector<char> > > BufferStream;

std::vector<char> buffer; BufferStream bufferStream( buffer );

write_view( bufferStream, const_view(image), png_tag() );

The data that ends up in buffer is identical to the data that ends up in foo.png from the first example if I don't open outputStream in binary mode.  So how can I make a binary memory stream with the iostreams library?  Do I need to write my own filter?

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Ok, so redefining bufferStream like so works:

std::stringstream bufferStream( std::ios_base::in | std::ios_base::out | std::ios_base::binary );

but it just feels "weird".  Is there any cleaner way to do this with the iostreams library?

This doesn't look weird to me. This is how I would do it. You should probably post this to the boost-users list. Chris

Chris Weed wrote:

On Sun, Mar 29, 2009 at 9:10 PM, Kenny Riddile <kfriddile@yahoo.com> wrote:

...

Kenny Riddile wrote:

...

I'm still pretty inexperienced with the iostreams library, so this may be a simple question. I'm trying to use GIL to write a PNG to a memory stream instead of a file stream. The write_view() function in the new version of GIL's io extension expects an ostream opened in binary mode as it's first parameter, such as:

using namespace std; using namespace boost::gil;

ofstream outputStream( "foo.png", ios::out | ios::binary ); write_view( outputStream, const_view(image), png_tag() );

I'm attempting to write to memory instead of a file, by doing this:

using namespace boost::gil; using namespace boost::iostreams;

typedef stream< back_insert_device< std::vector<char> > > BufferStream;

std::vector<char> buffer; BufferStream bufferStream( buffer );

write_view( bufferStream, const_view(image), png_tag() );

The data that ends up in buffer is identical to the data that ends up in foo.png from the first example if I don't open outputStream in binary mode. So how can I make a binary memory stream with the iostreams library? Do I need to write my own filter?

_______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

Ok, so redefining bufferStream like so works:

std::stringstream bufferStream( std::ios_base::in | std::ios_base::out | std::ios_base::binary );

but it just feels "weird". Is there any cleaner way to do this with the iostreams library?

This doesn't look weird to me. This is how I would do it.

Obviously I can use a typedef to hide the fact that it's a stringstream, but the weird part for me is accessing the data via: bufferStream.string().c_str() Of course, that can be abstracted too. I was just wondering if the iostreams library already offered some simple, elegant way of creating a binary memory stream before I reinvent the wheel.

You should probably post this to the boost-users list.

Honestly, I usually get better and more prompt responses when posting here than on the users list...I just go where the answers are.

Kim Barrett wrote:

At 7:41 PM -0500 3/29/09, Kenny Riddile wrote:

...

I'm attempting to write to memory instead of a file, by doing this:

using namespace boost::gil; using namespace boost::iostreams;

typedef stream< back_insert_device< std::vector<char> > > BufferStream;

std::vector<char> vbuffer; boost::iostreams::filtering_ostream outs( boost::iostreams::back_inserter(vbuffer))

is what I've been using to create an in-memory binary output stream. That is, a filtering stream that has only a sink and no intervening filters in the chain. _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

That still appears to be converting the data to characters, similar to opening a std::ofstream without explicitly putting it in binary mode.