e7b6ce1cf9
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@18848 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
175 lines
6.7 KiB
TeX
175 lines
6.7 KiB
TeX
\section{Bitmaps and icons overview}\label{wxbitmapoverview}
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Classes: \helpref{wxBitmap}{wxbitmap}, \helpref{wxBitmapHandler}{wxbitmaphandler}, \helpref{wxIcon}{wxicon}, \helpref{wxCursor}{wxcursor}.
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The wxBitmap class encapsulates the concept of a platform-dependent bitmap,
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either monochrome or colour. Platform-specific methods for creating a
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wxBitmap object from an existing file are catered for, and
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this is an occasion where conditional compilation will sometimes be
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required.
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A bitmap created dynamically or loaded from a file can be selected
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into a memory device context (instance of \helpref{wxMemoryDC}{wxmemorydc}). This
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enables the bitmap to be copied to a window or memory device context
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using \helpref{wxDC::Blit}{wxdcblit}, or to be used as a drawing surface. The {\bf
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wxToolBarSimple} class is implemented using bitmaps, and the toolbar demo
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shows one of the toolbar bitmaps being used for drawing a miniature
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version of the graphic which appears on the main window.
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See \helpref{wxMemoryDC}{wxmemorydc} for an example of drawing onto a bitmap.
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All wxWindows platforms support XPMs for small bitmaps and icons.
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You may include the XPM inline as below, since it's C code, or you
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can load it at run-time.
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\begin{verbatim}
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#include "mondrian.xpm"
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\end{verbatim}
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Sometimes you wish to use a .ico resource on Windows, and XPMs on
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other platforms (for example to take advantage of Windows' support for multiple icon resolutions).
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A macro, \helpref{wxICON}{wxiconmacro}, is available which creates an icon using an XPM
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on the appropriate platform, or an icon resource on Windows.
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\begin{verbatim}
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wxIcon icon(wxICON(mondrian));
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// Equivalent to:
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#if defined(__WXGTK__) || defined(__WXMOTIF__)
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wxIcon icon(mondrian_xpm);
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#endif
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#if defined(__WXMSW__)
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wxIcon icon("mondrian");
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#endif
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\end{verbatim}
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There is also a corresponding \helpref{wxBITMAP}{wxbitmapmacro} macro which allows
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to create the bitmaps in much the same way as \helpref{wxICON}{wxiconmacro} creates
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icons. It assumes that bitmaps live in resources under Windows or OS2 and XPM
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files under all other platforms (for XPMs, the corresponding file must be
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included before this macro is used, of course, and the name of the bitmap
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should be the same as the resource name under Windows with {\tt \_xpm}
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suffix). For example:
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\begin{verbatim}
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// an easy and portable way to create a bitmap
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wxBitmap bmp(wxBITMAP(bmpname));
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// which is roughly equivalent to the following
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#if defined(__WXMSW__) || defined(__WXPM__)
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wxBitmap bmp("bmpname", wxBITMAP_TYPE_RESOURCE);
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#else // Unix
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wxBitmap bmp(bmpname_xpm, wxBITMAP_TYPE_XPM);
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#endif
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\end{verbatim}
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You should always use wxICON and wxBITMAP macros because they work for any
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platform (unlike the code above which doesn't deal with wxMac, wxX11, ...) and
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are more short and clear than versions with {\tt \#ifdef}s. Even better,
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use the same XPMs on all platforms.
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\subsection{Supported bitmap file formats}\label{supportedbitmapformats}
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The following lists the formats handled on different platforms. Note
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that missing or partially-implemented formats are automatically supplemented
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by the \helpref{wxImage}{wximage} to load the data, and then converting
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it to wxBitmap form. Note that using wxImage is the preferred way to
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load images in wxWindows, with the exception of resources (XPM-files or
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native Windows resources). Writing an image format handler for wxImage
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is also far easier than writing one for wxBitmap, because wxImage has
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exactly one format on all platforms whereas wxBitmap can store pixel data
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very differently, depending on colour depths and platform.
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\wxheading{wxBitmap}
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Under Windows, wxBitmap may load the following formats:
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\begin{itemize}\itemsep=0pt
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\item Windows bitmap resource (wxBITMAP\_TYPE\_BMP\_RESOURCE)
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\item Windows bitmap file (wxBITMAP\_TYPE\_BMP)
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\item XPM data and file (wxBITMAP\_TYPE\_XPM)
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\item All formats that are supported by the \helpref{wxImage}{wximage} class.
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\end{itemize}
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Under wxGTK, wxBitmap may load the following formats:
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\begin{itemize}\itemsep=0pt
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\item XPM data and file (wxBITMAP\_TYPE\_XPM)
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\item All formats that are supported by the \helpref{wxImage}{wximage} class.
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\end{itemize}
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Under wxMotif and wxX11, wxBitmap may load the following formats:
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\begin{itemize}\itemsep=0pt
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\item XBM data and file (wxBITMAP\_TYPE\_XBM)
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\item XPM data and file (wxBITMAP\_TYPE\_XPM)
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\item All formats that are supported by the \helpref{wxImage}{wximage} class.
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\end{itemize}
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\wxheading{wxIcon}
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Under Windows, wxIcon may load the following formats:
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\begin{itemize}\itemsep=0pt
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\item Windows icon resource (wxBITMAP\_TYPE\_ICO\_RESOURCE)
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\item Windows icon file (wxBITMAP\_TYPE\_ICO)
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\item XPM data and file (wxBITMAP\_TYPE\_XPM)
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\end{itemize}
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Under wxGTK, wxIcon may load the following formats:
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\begin{itemize}\itemsep=0pt
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\item XPM data and file (wxBITMAP\_TYPE\_XPM)
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\item All formats that are supported by the \helpref{wxImage}{wximage} class.
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\end{itemize}
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Under wxMotif and wxX11, wxIcon may load the following formats:
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\begin{itemize}\itemsep=0pt
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\item XBM data and file (wxBITMAP\_TYPE\_XBM)
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\item XPM data and file (wxBITMAP\_TYPE\_XPM)
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\item All formats that are supported by the \helpref{wxImage}{wximage} class.
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\end{itemize}
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\wxheading{wxCursor}
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Under Windows, wxCursor may load the following formats:
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\begin{itemize}\itemsep=0pt
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\item Windows cursor resource (wxBITMAP\_TYPE\_CUR\_RESOURCE)
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\item Windows cursor file (wxBITMAP\_TYPE\_CUR)
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\item Windows icon file (wxBITMAP\_TYPE\_ICO)
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\item Windows bitmap file (wxBITMAP\_TYPE\_BMP)
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\end{itemize}
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Under wxGTK, wxCursor may load the following formats (in additional
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to stock cursors):
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\begin{itemize}\itemsep=0pt
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\item None (stock cursors only).
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\end{itemize}
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Under wxMotif and wxX11, wxCursor may load the following formats:
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\begin{itemize}\itemsep=0pt
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\item XBM data and file (wxBITMAP\_TYPE\_XBM)
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\end{itemize}
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\subsection{Bitmap format handlers}\label{bitmaphandlers}
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To provide extensibility, the functionality for loading and saving bitmap formats
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is not implemented in the wxBitmap class, but in a number of handler classes,
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derived from wxBitmapHandler. There is a static list of handlers which wxBitmap
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examines when a file load/save operation is requested. Some handlers are provided as standard, but if you
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have special requirements, you may wish to initialise the wxBitmap class with
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some extra handlers which you write yourself or receive from a third party.
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To add a handler object to wxBitmap, your application needs to include the header which implements it, and
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then call the static function \helpref{wxBitmap::AddHandler}{wxbitmapaddhandler}.
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{\bf Note:} bitmap handlers are not implemented on all platforms, and new ones rarely need
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to be implemented since wxImage can be used for loading most formats, as noted earlier.
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