\section{Bitmaps and icons overview}\label{wxbitmapoverview} Classes: \helpref{wxBitmap}{wxbitmap}, \helpref{wxBitmapHandler}{wxbitmaphandler}, \helpref{wxIcon}{wxicon}, \helpref{wxCursor}{wxcursor}. The wxBitmap class encapsulates the concept of a platform-dependent bitmap, either monochrome or colour. Platform-specific methods for creating a wxBitmap object from an existing file are catered for, and this is an occasion where conditional compilation will sometimes be required. A bitmap created dynamically or loaded from a file can be selected into a memory device context (instance of \helpref{wxMemoryDC}{wxmemorydc}). This enables the bitmap to be copied to a window or memory device context using \helpref{wxDC::Blit}{wxdcblit}, or to be used as a drawing surface. The {\bf wxToolBarSimple} class is implemented using bitmaps, and the toolbar demo shows one of the toolbar bitmaps being used for drawing a miniature version of the graphic which appears on the main window. See \helpref{wxMemoryDC}{wxmemorydc} for an example of drawing onto a bitmap. The following shows the conditional compilation required to load a bitmap under Unix and in Windows. The alternative is to use the string version of the bitmap constructor, which loads a file under Unix and a resource or file under Windows, but has the disadvantage of requiring the XPM icon file to be available at run-time. \begin{verbatim} #if defined(__WXGTK__) || defined(__WXMOTIF__) #include "mondrian.xpm" #endif \end{verbatim} A macro, \helpref{wxICON}{wxiconmacro}, is available which creates an icon using an XPM on the appropriate platform, or an icon resource on Windows. \begin{verbatim} wxIcon icon(wxICON(mondrian)); // Equivalent to: #if defined(__WXGTK__) || defined(__WXMOTIF__) wxIcon icon(mondrian_xpm); #endif #if defined(__WXMSW__) wxIcon icon("mondrian"); #endif \end{verbatim} There is also a corresponding \helpref{wxBITMAP}{wxbitmapmacro} macro which allows to create the bitmaps in much the same way as \helpref{wxICON}{wxiconmacro} creates icons. It assumes that bitmaps live in resources under Windows or OS2 and XPM files under all other platforms (for XPMs, the corresponding file must be included before this macro is used, of course, and the name of the bitmap should be the same as the resource name under Windows with {\tt \_xpm} suffix). For example: \begin{verbatim} // an easy and portable way to create a bitmap wxBitmap bmp(wxBITMAP(bmpname)); // which is roughly equivalent to the following #if defined(__WXMSW__) || defined(__WXPM__) wxBitmap bmp("bmpname", wxBITMAP_TYPE_RESOURCE); #else // Unix wxBitmap bmp(bmpname_xpm, wxBITMAP_TYPE_XPM); #endif \end{verbatim} You should always use wxICON and wxBITMAP macros because they work for any platform (unlike the code above which doesn't deal with wxMac, wxBe, ...) and are more short and clear than versions with {\tt #ifdef}s. \subsection{Supported bitmap file formats}\label{supportedbitmapformats} The following lists the formats handled on different platforms. Note that missing or partially-implemented formats are automatically supplemented by the \helpref{wxImage}{wximage} to load the data, and then converting it to wxBitmap form. Note that using wxImage is the preferred way to load images in wxWindows, with the exception of resources (XPM-files or native Windows resources). Writing an image format handler for wxImage is also far easier than writing one for wxBitmap, because wxImage has exactly one format on all platforms wheras wxBitmap can store pixel data very differently, depending on colour depths and platform. \wxheading{wxBitmap} Under Windows, wxBitmap may load the following formats: \begin{itemize}\itemsep=0pt \item Windows bitmap resource (wxBITMAP\_TYPE\_BMP\_RESOURCE) \item Windows bitmap file (wxBITMAP\_TYPE\_BMP) \item XPM data and file (wxBITMAP\_TYPE\_XPM) \item All formats that are supported by the \helpref{wxImage}{wximage} class. \end{itemize} Under wxGTK, wxBitmap may load the following formats: \begin{itemize}\itemsep=0pt \item XPM data and file (wxBITMAP\_TYPE\_XPM) \item All formats that are supported by the \helpref{wxImage}{wximage} class. \end{itemize} Under wxMotif, wxBitmap may load the following formats: \begin{itemize}\itemsep=0pt \item XBM data and file (wxBITMAP\_TYPE\_XBM) \item XPM data and file (wxBITMAP\_TYPE\_XPM) \item All formats that are supported by the \helpref{wxImage}{wximage} class. \end{itemize} \wxheading{wxIcon} Under Windows, wxIcon may load the following formats: \begin{itemize}\itemsep=0pt \item Windows icon resource (wxBITMAP\_TYPE\_ICO\_RESOURCE) \item Windows icon file (wxBITMAP\_TYPE\_ICO) \item XPM data and file (wxBITMAP\_TYPE\_XPM) \end{itemize} Under wxGTK, wxIcon may load the following formats: \begin{itemize}\itemsep=0pt \item XPM data and file (wxBITMAP\_TYPE\_XPM) \item All formats that are supported by the \helpref{wxImage}{wximage} class. \end{itemize} Under wxMotif, wxIcon may load the following formats: \begin{itemize}\itemsep=0pt \item XBM data and file (wxBITMAP\_TYPE\_XBM) \item XPM data and file (wxBITMAP\_TYPE\_XPM) \item All formats that are supported by the \helpref{wxImage}{wximage} class (?). \end{itemize} \wxheading{wxCursor} Under Windows, wxCursor may load the following formats: \begin{itemize}\itemsep=0pt \item Windows cursor resource (wxBITMAP\_TYPE\_CUR\_RESOURCE) \item Windows cursor file (wxBITMAP\_TYPE\_CUR) \item Windows icon file (wxBITMAP\_TYPE\_ICO) \item Windows bitmap file (wxBITMAP\_TYPE\_BMP) \end{itemize} Under wxGTK, wxCursor may load the following formats (in additional to stock cursors): \begin{itemize}\itemsep=0pt \item None (stock cursors only). \end{itemize} Under wxMotif, wxCursor may load the following formats: \begin{itemize}\itemsep=0pt \item XBM data and file (wxBITMAP\_TYPE\_XBM) \end{itemize} \subsection{Bitmap format handlers}\label{bitmaphandlers} To provide extensibility, the functionality for loading and saving bitmap formats is not implemented in the wxBitmap class, but in a number of handler classes, derived from wxBitmapHandler. There is a static list of handlers which wxBitmap examines when a file load/save operation is requested. Some handlers are provided as standard, but if you have special requirements, you may wish to initialise the wxBitmap class with some extra handlers which you write yourself or receive from a third party. To add a handler object to wxBitmap, your application needs to include the header which implements it, and then call the static function \helpref{wxBitmap::AddHandler}{wxbitmapaddhandler}. For example: {\small \begin{verbatim} #include #include ... // Initialisation wxBitmap::AddHandler(new wxPNGFileHandler); wxBitmap::AddHandler(new wxXPMFileHandler); wxBitmap::AddHandler(new wxXPMDataHandler); ... \end{verbatim} } Assuming the handlers have been written correctly, you should now be able to load and save PNG files and XPM files using the usual wxBitmap API. {\bf Note:} bitmap handlers are not implemented on all platforms. Currently, the above is only necessary on Windows, to save the extra overhead of formats that may not be necessary (if you don't use them, they are not linked into the executable). Unix platforms have PNG and XPM capability built-in (where supported).