docs/doxygen/overviews/bitmap.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        bitmap.h
   3 // Purpose:     topic overview
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows licence
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 /**
  10
  11 @page overview_bitmap Bitmaps and Icons
  12
  13 @tableofcontents
  14
  15 The wxBitmap class encapsulates the concept of a platform-dependent bitmap,
  16 either monochrome or colour. Platform-specific methods for creating a wxBitmap
  17 object from an existing file are catered for, and this is an occasion where
  18 conditional compilation will sometimes be required.
  19
  20 A bitmap created dynamically or loaded from a file can be selected into a
  21 memory device context (instance of wxMemoryDC). This enables the bitmap to be
  22 copied to a window or memory device context using wxDC::Blit(), or to be used
  23 as a drawing surface.
  24
  25 See wxMemoryDC for an example of drawing onto a bitmap.
  26
  27 All wxWidgets platforms support XPMs for small bitmaps and icons. You may
  28 include the XPM inline as below, since it's C code, or you can load it at
  29 run-time.
  30
  31 @code
  32 #include "sample.xpm"
  33 @endcode
  34
  35 Sometimes you wish to use a .ico resource on Windows, and XPMs on other
  36 platforms (for example to take advantage of Windows' support for multiple icon
  37 resolutions).
  38
  39 A macro, wxICON(), is available which creates an icon using an XPM on the
  40 appropriate platform, or an icon resource on Windows:
  41
  42 @code
  43 wxIcon icon(wxICON(sample));
  44
  45 // The above line is equivalent to this:
  46
  47 #if defined(__WXGTK__) || defined(__WXMOTIF__)
  48     wxIcon icon(sample_xpm);
  49 #endif
  50
  51 #if defined(__WXMSW__)
  52     wxIcon icon("sample");
  53 #endif
  54 @endcode
  55
  56 There is also a corresponding wxBITMAP() macro which allows to create the
  57 bitmaps in much the same way as wxICON() creates icons. It assumes that bitmaps
  58 live in resources under Windows or OS2 and XPM files under all other platforms
  59 (for XPMs, the corresponding file must be included before this macro is used,
  60 of course, and the name of the bitmap should be the same as the resource name
  61 under Windows with @c _xpm suffix). For example:
  62
  63 @code
  64 // an easy and portable way to create a bitmap
  65 wxBitmap bmp(wxBITMAP(bmpname));
  66
  67 // which is roughly equivalent to the following
  68 #if defined(__WXMSW__) || defined(__WXPM__)
  69     wxBitmap bmp("bmpname", wxBITMAP_TYPE_BMP_RESOURCE);
  70 #else // Unix
  71     wxBitmap bmp(bmpname_xpm, wxBITMAP_TYPE_XPM);
  72 #endif
  73 @endcode
  74
  75 You should always use wxICON() and wxBITMAP() macros because they work for any
  76 platform (unlike the code above which doesn't deal with wxMac, wxX11, ...) and
  77 are shorter and more clear than versions with many @ifdef_ blocks.
  78 Alternatively, you could use the same XPMs on all platforms and avoid dealing
  79 with Windows resource files.
  80
  81 If you'd like to embed bitmaps with alpha transparency in your program, neither
  82 XPM nor BMP formats are appropriate as they don't have support for alpha and
  83 another format, typically PNG, should be used. wxWidgets provides a similar
  84 helper for PNG bitmaps called wxBITMAP_PNG() that can be used to either load
  85 PNG files embedded in resources (meaning either Windows resource section of the
  86 executable file or OS X "Resource" subdirectory of the application bundle) or
  87 arrays containing PNG data included into the program code itself.
  88
  89 @see @ref group_class_gdi
  90
  91
  92
  93 @section overview_bitmap_supportedformats Supported Bitmap File Formats
  94
  95 The following lists the formats handled on different platforms. Note that
  96 missing or partially-implemented formats are automatically supplemented by
  97 using wxImage to load the data, and then converting it to wxBitmap form. Note
  98 that using wxImage is the preferred way to load images in wxWidgets, with the
  99 exception of resources (XPM-files or native Windows resources).
 100
 101 Writing an image format handler for wxImage is also far easier than writing one
 102 for wxBitmap, because wxImage has exactly one format on all platforms whereas
 103 wxBitmap can store pixel data very differently, depending on colour depths and
 104 platform.
 105
 106 @subsection overview_bitmap_supportedformats_bmp wxBitmap
 107
 108 Under Windows, wxBitmap may load the following formats:
 109
 110     @li Windows bitmap resource (wxBITMAP_TYPE_BMP_RESOURCE)
 111     @li Windows bitmap file (wxBITMAP_TYPE_BMP)
 112     @li XPM data and file (wxBITMAP_TYPE_XPM)
 113     @li All formats that are supported by the wxImage class.
 114
 115 Under wxGTK, wxBitmap may load the following formats:
 116
 117     @li XPM data and file (wxBITMAP_TYPE_XPM)
 118     @li All formats that are supported by the wxImage class.
 119
 120 Under wxMotif and wxX11, wxBitmap may load the following formats:
 121
 122     @li XBM data and file (wxBITMAP_TYPE_XBM)
 123     @li XPM data and file (wxBITMAP_TYPE_XPM)
 124     @li All formats that are supported by the wxImage class.
 125
 126 @subsection overview_bitmap_supportedformats_icon wxIcon
 127
 128 Under Windows, wxIcon may load the following formats:
 129
 130     @li Windows icon resource (wxBITMAP_TYPE_ICO_RESOURCE)
 131     @li Windows icon file (wxBITMAP_TYPE_ICO)
 132     @li XPM data and file (wxBITMAP_TYPE_XPM)
 133
 134 Under wxGTK, wxIcon may load the following formats:
 135
 136     @li XPM data and file (wxBITMAP_TYPE_XPM)
 137     @li All formats that are supported by the wxImage class.
 138
 139 Under wxMotif and wxX11, wxIcon may load the following formats:
 140
 141     @li XBM data and file (wxBITMAP_TYPE_XBM)
 142     @li XPM data and file (wxBITMAP_TYPE_XPM)
 143     @li All formats that are supported by the wxImage class.
 144
 145 @subsection overview_bitmap_supportedformats_cursor wxCursor
 146
 147 Under Windows, wxCursor may load the following formats:
 148
 149     @li Windows cursor resource (wxBITMAP_TYPE_CUR_RESOURCE)
 150     @li Windows cursor file (wxBITMAP_TYPE_CUR)
 151     @li Windows icon file (wxBITMAP_TYPE_ICO)
 152     @li Windows bitmap file (wxBITMAP_TYPE_BMP)
 153
 154 Under wxGTK, wxCursor may load the following formats (in addition to stock
 155 cursors):
 156
 157     @li None (stock cursors only).
 158
 159 Under wxMotif and wxX11, wxCursor may load the following formats:
 160
 161     @li XBM data and file (wxBITMAP_TYPE_XBM)
 162
 163
 164 @section overview_bitmap_handlers Bitmap Format Handlers
 165
 166 To provide extensibility, the functionality for loading and saving bitmap
 167 formats is not implemented in the wxBitmap class, but in a number of handler
 168 classes, derived from wxBitmapHandler. There is a static list of handlers which
 169 wxBitmap examines when a file load/save operation is requested.
 170
 171 Some handlers are provided as standard, but if you have special requirements,
 172 you may wish to initialise the wxBitmap class with some extra handlers which
 173 you write yourself or receive from a third party.
 174
 175 To add a handler object to wxBitmap, your application needs to include the
 176 header which implements it, and then call the static function
 177 wxBitmap::AddHandler().
 178
 179 @note Bitmap handlers are not implemented on all platforms, and new ones rarely
 180 need to be implemented since wxImage can be used for loading most formats, as
 181 noted earlier.
 182
 183 */
 184