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 Classes:
  14 @li wxBitmap
  15 @li wxBitmapHandler
  16 @li wxIcon
  17 @li wxCursor
  18
  19 The wxBitmap class encapsulates the concept of a platform-dependent bitmap,
  20 either monochrome or colour. Platform-specific methods for creating a wxBitmap
  21 object from an existing file are catered for, and this is an occasion where
  22 conditional compilation will sometimes be required.
  23
  24 A bitmap created dynamically or loaded from a file can be selected into a
  25 memory device context (instance of wxMemoryDC). This enables the bitmap to be
  26 copied to a window or memory device context using wxDC::Blit(), or to be used
  27 as a drawing surface.
  28
  29 See wxMemoryDC for an example of drawing onto a bitmap.
  30
  31 All wxWidgets platforms support XPMs for small bitmaps and icons. You may
  32 include the XPM inline as below, since it's C code, or you can load it at
  33 run-time.
  34
  35 @code
  36 #include "sample.xpm"
  37 @endcode
  38
  39 Sometimes you wish to use a .ico resource on Windows, and XPMs on other
  40 platforms (for example to take advantage of Windows' support for multiple icon
  41 resolutions).
  42
  43 A macro, wxICON(), is available which creates an icon using an XPM on the
  44 appropriate platform, or an icon resource on Windows:
  45
  46 @code
  47 wxIcon icon(wxICON(sample));
  48
  49 // The above line is equivalent to this:
  50
  51 #if defined(__WXGTK__) || defined(__WXMOTIF__)
  52     wxIcon icon(sample_xpm);
  53 #endif
  54
  55 #if defined(__WXMSW__)
  56     wxIcon icon("sample");
  57 #endif
  58 @endcode
  59
  60 There is also a corresponding wxBITMAP() macro which allows to create the
  61 bitmaps in much the same way as wxICON() creates icons. It assumes that bitmaps
  62 live in resources under Windows or OS2 and XPM files under all other platforms
  63 (for XPMs, the corresponding file must be included before this macro is used,
  64 of course, and the name of the bitmap should be the same as the resource name
  65 under Windows with @c _xpm suffix). For example:
  66
  67 @code
  68 // an easy and portable way to create a bitmap
  69 wxBitmap bmp(wxBITMAP(bmpname));
  70
  71 // which is roughly equivalent to the following
  72 #if defined(__WXMSW__) || defined(__WXPM__)
  73     wxBitmap bmp("bmpname", wxBITMAP_TYPE_BMP_RESOURCE);
  74 #else // Unix
  75     wxBitmap bmp(bmpname_xpm, wxBITMAP_TYPE_XPM);
  76 #endif
  77 @endcode
  78
  79 You should always use wxICON() and wxBITMAP() macros because they work for any
  80 platform (unlike the code above which doesn't deal with wxMac, wxX11, ...) and
  81 are shorter and more clear than versions with many @ifdef_ blocks.
  82 Alternatively, you could use the same XPMs on all platforms and avoid dealing
  83 with Windows resource files.
  84
  85 If you'd like to embed bitmaps with alpha transparency in your program, neither
  86 XPM nor BMP formats are appropriate as they don't have support for alpha and
  87 another format, typically PNG, should be used. wxWidgets provides a similar
  88 helper for PNG bitmaps called wxBITMAP_PNG() that can be used to either load
  89 PNG files embedded in resources (meaning either Windows resource section of the
  90 executable file or OS X "Resource" subdirectory of the application bundle) or
  91 arrays containing PNG data included into the program code itself.
  92
  93 @li @ref overview_bitmap_supportedformats
  94 @li @ref overview_bitmap_handlers
  95
  96
  97 <hr>
  98
  99
 100 @section overview_bitmap_supportedformats Supported Bitmap File Formats
 101
 102 The following lists the formats handled on different platforms. Note that
 103 missing or partially-implemented formats are automatically supplemented by
 104 using wxImage to load the data, and then converting it to wxBitmap form. Note
 105 that using wxImage is the preferred way to load images in wxWidgets, with the
 106 exception of resources (XPM-files or native Windows resources).
 107
 108 Writing an image format handler for wxImage is also far easier than writing one
 109 for wxBitmap, because wxImage has exactly one format on all platforms whereas
 110 wxBitmap can store pixel data very differently, depending on colour depths and
 111 platform.
 112
 113 @subsection overview_bitmap_supportedformats_bmp wxBitmap
 114
 115 Under Windows, wxBitmap may load the following formats:
 116
 117     @li Windows bitmap resource (wxBITMAP_TYPE_BMP_RESOURCE)
 118     @li Windows bitmap file (wxBITMAP_TYPE_BMP)
 119     @li XPM data and file (wxBITMAP_TYPE_XPM)
 120     @li All formats that are supported by the wxImage class.
 121
 122 Under wxGTK, wxBitmap may load the following formats:
 123
 124     @li XPM data and file (wxBITMAP_TYPE_XPM)
 125     @li All formats that are supported by the wxImage class.
 126
 127 Under wxMotif and wxX11, wxBitmap may load the following formats:
 128
 129     @li XBM data and file (wxBITMAP_TYPE_XBM)
 130     @li XPM data and file (wxBITMAP_TYPE_XPM)
 131     @li All formats that are supported by the wxImage class.
 132
 133 @subsection overview_bitmap_supportedformats_icon wxIcon
 134
 135 Under Windows, wxIcon may load the following formats:
 136
 137     @li Windows icon resource (wxBITMAP_TYPE_ICO_RESOURCE)
 138     @li Windows icon file (wxBITMAP_TYPE_ICO)
 139     @li XPM data and file (wxBITMAP_TYPE_XPM)
 140
 141 Under wxGTK, wxIcon may load the following formats:
 142
 143     @li XPM data and file (wxBITMAP_TYPE_XPM)
 144     @li All formats that are supported by the wxImage class.
 145
 146 Under wxMotif and wxX11, wxIcon may load the following formats:
 147
 148     @li XBM data and file (wxBITMAP_TYPE_XBM)
 149     @li XPM data and file (wxBITMAP_TYPE_XPM)
 150     @li All formats that are supported by the wxImage class.
 151
 152 @subsection overview_bitmap_supportedformats_cursor wxCursor
 153
 154 Under Windows, wxCursor may load the following formats:
 155
 156     @li Windows cursor resource (wxBITMAP_TYPE_CUR_RESOURCE)
 157     @li Windows cursor file (wxBITMAP_TYPE_CUR)
 158     @li Windows icon file (wxBITMAP_TYPE_ICO)
 159     @li Windows bitmap file (wxBITMAP_TYPE_BMP)
 160
 161 Under wxGTK, wxCursor may load the following formats (in addition to stock
 162 cursors):
 163
 164     @li None (stock cursors only).
 165
 166 Under wxMotif and wxX11, wxCursor may load the following formats:
 167
 168     @li XBM data and file (wxBITMAP_TYPE_XBM)
 169
 170
 171 @section overview_bitmap_handlers Bitmap Format Handlers
 172
 173 To provide extensibility, the functionality for loading and saving bitmap
 174 formats is not implemented in the wxBitmap class, but in a number of handler
 175 classes, derived from wxBitmapHandler. There is a static list of handlers which
 176 wxBitmap examines when a file load/save operation is requested.
 177
 178 Some handlers are provided as standard, but if you have special requirements,
 179 you may wish to initialise the wxBitmap class with some extra handlers which
 180 you write yourself or receive from a third party.
 181
 182 To add a handler object to wxBitmap, your application needs to include the
 183 header which implements it, and then call the static function
 184 wxBitmap::AddHandler().
 185
 186 @note Bitmap handlers are not implemented on all platforms, and new ones rarely
 187 need to be implemented since wxImage can be used for loading most formats, as
 188 noted earlier.
 189
 190 */
 191