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Skeeter Dropped Image Format

This describes a simple BMessage format which is used to drag and drop images from the preview area of the Skeeter scanning utility. I was surprised that none of the existing image editing applications supported a BBitmap dragged image format, so I made one up which is simple to implement. I'm not really tied or commited to this until a bunch of people have implemented it, so if someone comes up with something better I'd be willing to take a look. The RRaster format looked fine, but I thought this would be better, to take advantage of the encapsulation inherent in an archived BMessage.

The following is included in the header file DraggedImage.h in the Skeeter distribution:

    // Constants for a simple BMessage format for an image being dragged.
    // When you see a dropped DRAGGED_IMAGE_MESSAGE message, you can recover
    // check the color space, width, and height of the message, and if it's
    // to your liking call BBitmap::Instantiate() to recover the BBitmap.

    #define DRAGGED_IMAGE_MESSAGE       'Idrg'
    #define kDraggedImageColorSpace     "color_space"   // B_INT32_TYPE
    #define kDraggedImageWidth          "width"         // B_INT32_TYPE
    #define kDraggedImageHeight         "height"        // B_INT32_TYPE

The method for unpacking the bitmap is trivial. In the MessageReceived() function of your view receiving the drop, you add this code (adding appropriate error checking, of course):

    switch( msg->what ) {
      .
      .
      .
    case DRAGGED_IMAGE_MESSAGE:
        if( msg->WasDropped() ) {
            int32 space, width, height;
            msg->FindInt32( kDraggedImageColorSpace, &space );
            msg->FindInt32( kDraggedImageWidth, &width );
            msg->FindInt32( kDraggedImageHeight, &height);
            // check if they're what you want
            if( check_bitmap_values( space, width, height ) ) {
                BBitmap *bits = BBitmap::Instantiate( msg );
                if( bits )
                    do_stuff_with_bitmap( bits );
            }
        }
        break;
      .
      .
      .
    }

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