docs/latex/wx/tbitmap.tex

   1 \section{Bitmaps and icons overview}\label{wxbitmapoverview}
   2
   3 Classes: \helpref{wxBitmap}{wxbitmap}, \helpref{wxBitmapHandler}{wxbitmaphandler}, \helpref{wxIcon}{wxicon}, \helpref{wxCursor}{wxcursor}.
   4
   5 The wxBitmap class encapsulates the concept of a platform-dependent bitmap,
   6 either monochrome or colour. Platform-specific methods for creating a
   7 wxBitmap object from an existing file are catered for, and
   8 this is an occasion where conditional compilation will sometimes be
   9 required.
  10
  11 A bitmap created dynamically or loaded from a file can be selected
  12 into a memory device context (instance of \helpref{wxMemoryDC}{wxmemorydc}). This
  13 enables the bitmap to be copied to a window or memory device context
  14 using \helpref{wxDC::Blit}{wxdcblit}, or to be used as a drawing surface.  The {\bf
  15 wxToolBarSimple} class is implemented using bitmaps, and the toolbar demo
  16 shows one of the toolbar bitmaps being used for drawing a miniature
  17 version of the graphic which appears on the main window.
  18
  19 See \helpref{wxMemoryDC}{wxmemorydc} for an example of drawing onto a bitmap.
  20
  21 The following shows the conditional compilation required to load a
  22 bitmap under Unix and in Windows. The alternative is to use the string
  23 version of the bitmap constructor, which loads a file under Unix and a
  24 resource or file under Windows, but has the disadvantage of requiring the
  25 XPM icon file to be available at run-time.
  26
  27 \begin{verbatim}
  28 #if defined(__WXGTK__) || defined(__WXMOTIF__)
  29 #include "mondrian.xpm"
  30 #endif
  31 \end{verbatim}
  32
  33 A macro, \helpref{wxICON}{wxicon}, is available which creates an icon using an XPM
  34 on the appropriate platform, or an icon resource on Windows.
  35
  36 \begin{verbatim}
  37 wxIcon icon(wxICON(mondrian));
  38
  39 // Equivalent to:
  40
  41 #if defined(__WXGTK__) || defined(__WXMOTIF__)
  42 wxIcon icon(mondrian_xpm);
  43 #endif
  44
  45 #if defined(__WXMSW__)
  46 wxIcon icon("mondrian");
  47 #endif
  48 \end{verbatim}
  49
  50 There is also a corresponding \helpref{wxBITMAP}{wxbitmap} macro which allows
  51 to create the bitmaps in much the same way as \helpref{wxICON}{wxicon} creates
  52 icons. It assumes that bitmaps live in resources under Windows or OS2 and XPM
  53 files under all other platforms (for XPMs, the corresponding file must be
  54 included before this macro is used, of course, and the name of the bitmap
  55 should be the same as the resource name under Windows with {\tt \_xpm}
  56 suffix). For example:
  57
  58 \begin{verbatim}
  59 // an easy and portable way to create a bitmap
  60 wxBitmap bmp(wxBITMAP(bmpname));
  61
  62 // which is roughly equivalent to the following
  63 #if defined(__WXMSW__) || defined(__WXPM__)
  64     wxBitmap bmp("bmpname", wxBITMAP_TYPE_RESOURCE);
  65 #else // Unix
  66     wxBitmap bmp(bmpname_xpm, wxBITMAP_TYPE_XPM);
  67 #endif
  68 \end{verbatim}
  69
  70 You should always use wxICON and wxBITMAP macros because they work for any
  71 platform (unlike the code above which doesn't deal with wxMac, wxBe, ...) and
  72 are more short and clear than versions with {\tt #ifdef}s.
  73
  74 \subsection{Supported bitmap file formats}\label{supportedbitmapformats}
  75
  76 The following lists the formats handled on different platforms. Note
  77 that missing or partially-implemented formats can be supplemented
  78 by using \helpref{wxImage}{wximage} to load the data, and then converting
  79 it to wxBitmap form.
  80
  81 \wxheading{wxBitmap}
  82
  83 Under Windows, wxBitmap may load the following formats:
  84
  85 \begin{itemize}\itemsep=0pt
  86 \item Windows bitmap resource (wxBITMAP\_TYPE\_BMP\_RESOURCE)
  87 \item Windows bitmap file (wxBITMAP\_TYPE\_BMP)
  88 \item PNG file (wxBITMAP\_TYPE\_PNG). Currently 4-bit (16-colour) PNG files do not load properly.
  89 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
  90 \end{itemize}
  91
  92 Under wxGTK, wxBitmap may load the following formats:
  93
  94 \begin{itemize}\itemsep=0pt
  95 \item Windows bitmap file (wxBITMAP\_TYPE\_BMP)
  96 \item PNG (wxBITMAP\_TYPE\_PNG).
  97 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
  98 \end{itemize}
  99
 100 Under wxMotif, wxBitmap may load the following formats:
 101
 102 \begin{itemize}\itemsep=0pt
 103 %\item Windows bitmap file (wxBITMAP\_TYPE\_BMP)
 104 %\item PNG (wxBITMAP\_TYPE\_PNG).
 105 \item XBM data and file (wxBITMAP\_TYPE\_XBM)
 106 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
 107 \end{itemize}
 108
 109 \wxheading{wxIcon}
 110
 111 Under Windows, wxIcon may load the following formats:
 112
 113 \begin{itemize}\itemsep=0pt
 114 \item Windows icon resource (wxBITMAP\_TYPE\_ICO\_RESOURCE)
 115 \item Windows icon file (wxBITMAP\_TYPE\_ICO)
 116 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
 117 \end{itemize}
 118
 119 Under wxGTK, wxIcon may load the following formats:
 120
 121 \begin{itemize}\itemsep=0pt
 122 \item PNG (wxBITMAP\_TYPE\_PNG).
 123 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
 124 \end{itemize}
 125
 126 Under wxMotif, wxIcon may load the following formats:
 127
 128 \begin{itemize}\itemsep=0pt
 129 %\item Windows bitmap file (wxBITMAP\_TYPE\_BMP)
 130 %\item PNG (wxBITMAP\_TYPE\_PNG).
 131 \item XBM data and file (wxBITMAP\_TYPE\_XBM)
 132 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
 133 \end{itemize}
 134
 135 \wxheading{wxCursor}
 136
 137 Under Windows, wxCursor may load the following formats:
 138
 139 \begin{itemize}\itemsep=0pt
 140 \item Windows cursor resource (wxBITMAP\_TYPE\_CUR\_RESOURCE)
 141 \item Windows cursor file (wxBITMAP\_TYPE\_CUR)
 142 \item Windows icon file (wxBITMAP\_TYPE\_ICO)
 143 \item Windows bitmap file (wxBITMAP\_TYPE\_BMP)
 144 \end{itemize}
 145
 146 Under wxGTK, wxCursor may load the following formats (in additional
 147 to stock cursors):
 148
 149 \begin{itemize}\itemsep=0pt
 150 \item None (stock cursors only).
 151 \end{itemize}
 152
 153 Under wxMotif, wxCursor may load the following formats:
 154
 155 \begin{itemize}\itemsep=0pt
 156 \item XBM data and file (wxBITMAP\_TYPE\_XBM)
 157 \end{itemize}
 158
 159 \subsection{Bitmap format handlers}\label{bitmaphandlers}
 160
 161 To provide extensibility, the functionality for loading and saving bitmap formats
 162 is not implemented in the wxBitmap class, but in a number of handler classes,
 163 derived from wxBitmapHandler. There is a static list of handlers which wxBitmap
 164 examines when a file load/save operation is requested. Some handlers are provided as standard, but if you
 165 have special requirements, you may wish to initialise the wxBitmap class with
 166 some extra handlers which you write yourself or receive from a third party.
 167
 168 To add a handler object to wxBitmap, your application needs to include the header which implements it, and
 169 then call the static function \helpref{wxBitmap::AddHandler}{wxbitmapaddhandler}. For example:
 170
 171 {\small
 172 \begin{verbatim}
 173   #include <wx/pnghand.h>
 174   #include <wx/xpmhand.h>
 175   ...
 176   // Initialisation
 177   wxBitmap::AddHandler(new wxPNGFileHandler);
 178   wxBitmap::AddHandler(new wxXPMFileHandler);
 179   wxBitmap::AddHandler(new wxXPMDataHandler);
 180   ...
 181 \end{verbatim}
 182 }
 183
 184 Assuming the handlers have been written correctly, you should now be able to load and save PNG files
 185 and XPM files using the usual wxBitmap API.
 186
 187 {\bf Note:} bitmap handlers are not implemented on all platforms. Currently, the above is only necessary on
 188 Windows, to save the extra overhead of formats that may not be necessary (if you don't use them, they
 189 are not linked into the executable). Unix platforms have PNG and XPM capability built-in (where supported).
 190