Find out png color type using png++

I'm using png++, which is working ok, but you need to set th开发者_运维技巧e pixel type as a template parameter:

 png::image< png::rgb_pixel > image("input.png");

The problem is I don't know at compile time whether it is rgb, rgba etc. Can't seem to find a way to get png++ to tell me what info is actually in the png.

Any ideas?

Thanks.

Hey, author of png++ here to help :)

If you really need to know what pixel format is in the PNG image, using png::reader is the supported way:

png::reader< std::istream > reader(my_stream);
reader.read_info();
png::color_type color_type = reader.get_color_type();

However, if you don't care of the image color type and just want to load it into, e.g. RGBA buffer, I'd suggest using png::image< rgba_pixel > image("input.png"): this will automagically convert PNG image of any color type to RGBA for you.

Try using a reader. Then check out the member functions of it's base class, io_base. I think it has what you're looking for.