Furthermore Thumbnail requires libprefs.so from Jon Watte to save its preferences. This shared library must be installed in the home/config/lib folder or anywhere else the BeOS can find it. (The Thumbnail distribution contains libprefs.so from the version 1.2.5 of the libprefs package.)

(Thumbnail requires a shared library named libThumbnail.so which comes with the Thumbnail distribution and must be installed in the home/config/lib folder or anywhere else the BeOS can find it.

The preference window can be accessed by selecting the Preferences menu item in the Thumbnail window.

On the "Thumbnail Creation" tab you can mark if alerts telling that the format of a specific file has not been understood shall be suppressed, if icons or the large thumbnail shall be shown and/or written into attributes (written icons/thumbnails are always shown), if the large thumbnail shall be dithered to the 8 Bit color palette instead of being created as true color image and if the resolution of the original image shall be written into a width and height attribute.

On the "MIME Database" tab you can mark if the MIME database shall be updated each time Thumbnail is launched. This updating adds a width and a height attribute to each subtype of image if not already present. This makes it possible to view the width and height attributes of image files with the Tracker.

Description of the buttons:

• Revert: display prefs which are currently used.
• Reload: display saved prefs.
• Defaults: display default values.
• Use: use displayed prefs (without saving them to disk).
• Save: save displayed prefs and use them.

• Creating Thumbnails:
  To create thumbnails, send a standard B_REFS_RECEIVED message. This is not a real scripting message, but can be sent by "hey": hey Thumbnail load "file(full-path-to-file)"
• Changing Preferences:
  Thumbnail has a property named "Preferences" which in turn has a property named "Thumbnail Creation" (this is the grouping tab in the preferences window). This property serves as a root group for preferences and understands the suite named "suite/vnd.dragonfly-pref-group" in addition to the standard suite "suite/vnd.Be-handler". The root group contains preferences or preference groups. A preference understands the suite named "suite/vnd.dragonfly-pref" in addition to the standard suite "suite/vnd.Be-handler", whereas a preference group just understands the standard suite "suite/vnd.Be-handler".

suite/vnd.dragonfly-pref-root

suite/vnd.dragonfly-pref

Examples:

• Mini Icon

  This is the standard mini icon displayed by the tracker.

  Name: BEOS:M:STD_ICON
  Type: 'MICN'

• Large Icon

  This is the standard large icon displayed by the tracker.

  Name: BEOS:L:STD_ICON
  Type: 'ICON'

• Thumbnail

  The longest side of the thumbnail is 96 pixels long (or smaller if the original image has been smaller). The other side is scaled with the aspect of the original image. The thumbnail is a BBitmap which has been archived into a BMessage which has been flattened and then been written into the attribute. The color space of the BBitmap is either B_COLOR_8_BIT (if dithering was checked) or B_RGB_32_BIT.

  Name: GRAFX:Thumbnail
  Type: B_MESSAGE_TYPE ('MSGG')
  Format: Flattened BMessage. The unflattened BMessage is a BBitmap archive.

• Width

  Name: GRAFX:Width
  Type: B_INT32_TYPE ('LONG')
  Format: int32

• Height

  Name: GRAFX:Height
  Type: B_INT32_TYPE ('LONG')
  Format: int32

Source Code and shared library

// bitmap is assumed to be a BBitmap-pointer of an image
// for which you want to create a thumbnail
// view is assumed to be a BView where you want to display
// the thumbnail
// ref is assumed to be an entry_ref to the file where the image
// comes from

bool dither = true;         // the thumbnail will be dithered
DThumbnail thumbnail(bitmap, dither);

if (thumbnail->Bitmap())    // will be NULL if the thumbnail couldn't be created
{
    view->DrawBitmap(thumbnail->Bitmap());

    BNode node(&ref);
    thumbnail->WriteThumbnailAttribute(&node);
    thumbnail->WriteIconAttribute(&node);
    thumbnail->WriteMiniIconAttribute(&node);
    thumbnail->WriteResolutionAttributes(&node);
}