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}{wxiconmacro}, 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}{wxbitmapmacro} macro which allows
  51 to create the bitmaps in much the same way as \helpref{wxICON}{wxiconmacro} 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 are automatically supplemented
  78 by the \helpref{wxImage}{wximage} to load the data, and then converting
  79 it to wxBitmap form. Note that using wxImage is the preferred way to
  80 load images in wxWindows, with the exception of resources (XPM-files or
  81 native Windows resources). Writing an image format handler for wxImage
  82 is also far easier than writing one for wxBitmap, because wxImage has
  83 exactly one format on all platforms wheras wxBitmap can store pixel data
  84 very differently, depending on colour depths and platform.
  85
  86 \wxheading{wxBitmap}
  87
  88 Under Windows, wxBitmap may load the following formats:
  89
  90 \begin{itemize}\itemsep=0pt
  91 \item Windows bitmap resource (wxBITMAP\_TYPE\_BMP\_RESOURCE)
  92 \item Windows bitmap file (wxBITMAP\_TYPE\_BMP)
  93 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
  94 \item All formats that are supported by the \helpref{wxImage}{wximage} class.
  95 \end{itemize}
  96
  97 Under wxGTK, wxBitmap may load the following formats:
  98
  99 \begin{itemize}\itemsep=0pt
 100 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
 101 \item All formats that are supported by the \helpref{wxImage}{wximage} class.
 102 \end{itemize}
 103
 104 Under wxMotif, wxBitmap may load the following formats:
 105
 106 \begin{itemize}\itemsep=0pt
 107 \item XBM data and file (wxBITMAP\_TYPE\_XBM)
 108 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
 109 \item All formats that are supported by the \helpref{wxImage}{wximage} class.
 110 \end{itemize}
 111
 112 \wxheading{wxIcon}
 113
 114 Under Windows, wxIcon may load the following formats:
 115
 116 \begin{itemize}\itemsep=0pt
 117 \item Windows icon resource (wxBITMAP\_TYPE\_ICO\_RESOURCE)
 118 \item Windows icon file (wxBITMAP\_TYPE\_ICO)
 119 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
 120 \end{itemize}
 121
 122 Under wxGTK, wxIcon may load the following formats:
 123
 124 \begin{itemize}\itemsep=0pt
 125 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
 126 \item All formats that are supported by the \helpref{wxImage}{wximage} class.
 127 \end{itemize}
 128
 129 Under wxMotif, wxIcon may load the following formats:
 130
 131 \begin{itemize}\itemsep=0pt
 132 \item XBM data and file (wxBITMAP\_TYPE\_XBM)
 133 \item XPM data and file (wxBITMAP\_TYPE\_XPM)
 134 \item All formats that are supported by the \helpref{wxImage}{wximage} class (?).
 135 \end{itemize}
 136
 137 \wxheading{wxCursor}
 138
 139 Under Windows, wxCursor may load the following formats:
 140
 141 \begin{itemize}\itemsep=0pt
 142 \item Windows cursor resource (wxBITMAP\_TYPE\_CUR\_RESOURCE)
 143 \item Windows cursor file (wxBITMAP\_TYPE\_CUR)
 144 \item Windows icon file (wxBITMAP\_TYPE\_ICO)
 145 \item Windows bitmap file (wxBITMAP\_TYPE\_BMP)
 146 \end{itemize}
 147
 148 Under wxGTK, wxCursor may load the following formats (in additional
 149 to stock cursors):
 150
 151 \begin{itemize}\itemsep=0pt
 152 \item None (stock cursors only).
 153 \end{itemize}
 154
 155 Under wxMotif, wxCursor may load the following formats:
 156
 157 \begin{itemize}\itemsep=0pt
 158 \item XBM data and file (wxBITMAP\_TYPE\_XBM)
 159 \end{itemize}
 160
 161 \subsection{Bitmap format handlers}\label{bitmaphandlers}
 162
 163 To provide extensibility, the functionality for loading and saving bitmap formats
 164 is not implemented in the wxBitmap class, but in a number of handler classes,
 165 derived from wxBitmapHandler. There is a static list of handlers which wxBitmap
 166 examines when a file load/save operation is requested. Some handlers are provided as standard, but if you
 167 have special requirements, you may wish to initialise the wxBitmap class with
 168 some extra handlers which you write yourself or receive from a third party.
 169
 170 To add a handler object to wxBitmap, your application needs to include the header which implements it, and
 171 then call the static function \helpref{wxBitmap::AddHandler}{wxbitmapaddhandler}. For example:
 172
 173 {\small
 174 \begin{verbatim}
 175   #include <wx/pnghand.h>
 176   #include <wx/xpmhand.h>
 177   ...
 178   // Initialisation
 179   wxBitmap::AddHandler(new wxPNGFileHandler);
 180   wxBitmap::AddHandler(new wxXPMFileHandler);
 181   wxBitmap::AddHandler(new wxXPMDataHandler);
 182   ...
 183 \end{verbatim}
 184 }
 185
 186 Assuming the handlers have been written correctly, you should now be able to load and save PNG files
 187 and XPM files using the usual wxBitmap API.
 188
 189 {\bf Note:} bitmap handlers are not implemented on all platforms. Currently, the above is only necessary on
 190 Windows, to save the extra overhead of formats that may not be necessary (if you don't use them, they
 191 are not linked into the executable). Unix platforms have PNG and XPM capability built-in (where supported).
 192