docs/doxygen/overviews/bitmap.h

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