QPixmap(3qt)QPixmap(3qt)NAMEQPixmap - Off-screen pixel-based paint device
#include <qpixmap.h>
Inherits QPaintDevice and Qt.
Inherited by QBitmap and QCanvasPixmap.
Public Members
enum ColorMode { Auto, Color, Mono }
enum Optimization { DefaultOptim, NoOptim,
MemoryOptim=NoOptim, NormalOptim, BestOptim }
QPixmap ()
QPixmap ( int w, int h, int depth = -1, Optimization =
DefaultOptim )
QPixmap ( const QSize &, int depth = -1, Optimization =
DefaultOptim )
QPixmap ( const QString & fileName, const char * format=0,
ColorMode mode=Auto )
QPixmap ( const QString & fileName, const char * format,
int conversion_flags )
QPixmap ( const char * xpm[] )
QPixmap ( const QByteArray & data )
QPixmap ( const QPixmap & )
~QPixmap ()
QPixmap& operator= ( const QPixmap & )
QPixmap& operator= ( const QImage & )
bool isNull () const
int width () const
int height () const
QSize size () const
QRect rect () const
int depth () const
void fill ( const QColor & fillColor = Qt::white )
void fill ( const QWidget *, int xofs, int yofs )
void fill ( const QWidget *, const QPoint & ofs )
void resize ( int width, int height )
void resize ( const QSize & )
const QBitmap* mask () const
void setMask ( const QBitmap & )
bool selfMask () const
QBitmap createHeuristicMask ( bool clipTight = TRUE )
const
QPixmap xForm ( const QWMatrix & ) const
QImage convertToImage () const
bool convertFromImage ( const QImage &, ColorMode
mode=Auto )
bool convertFromImage ( const QImage &, int
conversion_flags )
bool load ( const QString & fileName, const char *
format=0, ColorMode mode=Auto )
bool load ( const QString & fileName, const char * format,
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QPixmap(3qt)QPixmap(3qt)
int conversion_flags )
bool loadFromData ( const uchar * buf, uint len, const
char * format=0, ColorMode mode=Auto )
bool loadFromData ( const uchar * buf, uint len, const
char * format, int conversion_flags )
bool loadFromData ( const QByteArray & data, const char *
format=0, int conversion_flags=0 )
bool save ( const QString & fileName, const char * format
) const
bool save ( const QString & fileName, const char * format,
int quality ) const
int serialNumber () const
Optimization optimization () const
void setOptimization ( Optimization )
virtual void detach ()
bool isQBitmap () const
Static Public Members
int defaultDepth ()
QPixmap grabWindow ( WId, int x=0, int y=0, int w=-1, int
h=-1 )
QPixmap grabWidget ( QWidget * widget, int x=0, int y=0,
int w=-1, int h=-1 )
QWMatrix trueMatrix ( const QWMatrix &, int w, int h )
const char* imageFormat ( const QString & fileName )
Optimization defaultOptimization ()
void setDefaultOptimization ( Optimization )
Protected Members
QPixmap ( int w, int h, const uchar * data, bool isXbitmap
)
virtual int metric ( int ) const
RELATED FUNCTION DOCUMENTATION
(Note that these are not member functions.)
QDataStream & operator>> (QDataStream & s, QPixmap &
pixmap)
QDataStream & operator<< (QDataStream & s, const QPixmap &
pixmap)
DESCRIPTION
The QPixmap class is an off-screen pixel-based paint
device.
It is one of the two classes Qt provides for dealing with
images, the other being QImage. QPixmap is designed and
optimized for drawing; QImage is designed and optimized
for I/O and for direct pixel access/manipulation. There
are (slow) functions to convert between QImage and
QPixmap; convertToImage() and convertFromImage().
One common use of the QPixmap class is to enable smooth
updating of widgets. Whenever something complex needs to
be drawn, you can use a pixmap to obtain flicker-free
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QPixmap(3qt)QPixmap(3qt)
drawing, like this:
1 Create a pixmap with the same size as the widget.
2 Fill the pixmap with the widget background color.
3 Paint the pixmap.
4 bitBlt() the pixmap contents onto the widget.
Pixel data in a pixmap is internal and managed by the
underlying window system. Pixels can only be accessed
through QPainter functions, through bitBlt(), and by
converting the QPixmap to a QImage.
You can display a QPixmap on the screen easily using e.g.
QLabel::setPixmap(), and all the QButton subclasses
support pixmap use.
The QPixmap class uses lazy copying, so it is practical to
pass pass QPixmap objects as arguments.
Note about Windows 95 and 98: On Windows 9x, the system
crashes if you create more than approximately 1000
pixmaps, independent of the size of the pixmaps or
installed RAM. Windows NT does not have this limitation.
Qt tries to work around the resource limitation. If you
set the pixmap optimization to QPixmap::MemoryOptim and
the width of your pixmap is less than or equal to 128
pixels, Qt stores the pixmap in a way which is very
memory-efficient when there are many pixmaps.
If your application uses dozens or hundreds of pixmaps,
e.g. on tool bar buttons, in popup menus, and you plan to
run it on Windows 95 or Windows 98, then we recommend
using code like this:
QPixmap::setDefaultOptimization( QPixmap::MemoryOptim );
while ( ... ) {
// load tool bar pixmaps etc.
QPixmap *pixmap = new QPixmap(fileName);
}
QPixmap::setDefaultOptimization( QPixmap::NormalOptim );
See also QBitmap, QImage, QImageIO and Shared Classes
Examples: qtimage/qtimage.cpp grapher/grapher.cpp
xform/xform.cpp menu/menu.cpp qmag/qmag.cpp
desktop/desktop.cpp scrollview/scrollview.cpp
movies/main.cpp picture/picture.cpp
Member Type Documentation
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QPixmap(3qt)QPixmap(3qt)QPixmap::ColorMode
This enum type defines the color modes that exist for
converting QImage objects to QPixmap. The current values
are:
Auto - select Color or Mono on a case-by-case basis.
Color - always create colored pixmaps.
Mono - always create bitmaps.
QPixmap::OptimizationQPixmap has the choice of optimizing for speed or memory
in a few places, and the best choice varies from pixmap to
pixmap, but can generally be derived heuristically. This
enum type defines a number of optimization modes you can
set for any pixmap, to tweak the speed/memory tradeoffs:
DefaultOptim - whatever QPixmap::defaultOptimization()
returns. A pixmap with this optimization mode set always
has the default optimization type, even if the default is
changed with setDefaultOptimization().
NoOptim - no optimization (currently the same as
MemoryOptim).
MemoryOptim - optimize for minimal memory use.
NormalOptim - optimize for typical usage. Often uses more
memory than MemoryOptim, and often faster.
BestOptim - optimize for pixmaps that are drawn very often
and where performance is critical. Generally uses more
memory than NormalOptim and may provide a little better
speed.
We recommend sticking with DefaultOptim
MEMBER FUNCTION DOCUMENTATIONQPixmap::QPixmap ()
Constructs a null pixmap.
See also isNull().
QPixmap::QPixmap ( const QByteArray & img_data )
Constructs a pixmaps by loading from img_data. The data
can be in any image format supported by Qt.
See also loadFromData().
QPixmap::QPixmap ( const QString & fileName, const char * format,
int conversion_flags )
Constructs a pixmap from the file fileName. If the file
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QPixmap(3qt)QPixmap(3qt)
does not exist, or is of an unknown format, the pixmap
becomes a null pixmap.
The parameters are passed on to load().
See also isNull(), load(), loadFromData(), save() and
imageFormat().
QPixmap::QPixmap ( const QString & fileName, const char *
format=0, ColorMode mode=Auto )
Constructs a pixmap from the file fileName. If the file
does not exist, or is of an unknown format, the pixmap
becomes a null pixmap.
The parameters are passed on to load().
See also isNull(), load(), loadFromData(), save() and
imageFormat().
QPixmap::QPixmap ( const QPixmap & pixmap )
Constructs a pixmap which is a copy of pixmap.
QPixmap::QPixmap ( const char * xpm[] )
Constructs a pixmap from xpm, which must be a valid XPM
image.
Error are silently ignored.
Note that it's possible to squeeze the XPM variable a
little bit by using an unusual declaration:
static const char * const start_xpm[]={
"16 15 8 1",
"a c #cec6bd",
....
The extra const makes the entire definition read-only,
which is slightly more efficient e.g. when the code is in
a shared library, and ROMable when the application is to
be stored in ROM.
In order to use that sort of declaration, you must cast
the variable back to <nobr>const char **</nobr> when you
create the QPixmap.
QPixmap::QPixmap ( int w, int h, const uchar * bits, bool
isXbitmap ) [protected]
Constructs a monochrome pixmap which is initialized with
the data in bits. This constructor is protected and used
by the QBitmap class.
QPixmap::QPixmap ( int w, int h, int depth = -1, Optimization
optimization = DefaultOptim )
Constructs a pixmap with w width, h height and of depth
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QPixmap(3qt)QPixmap(3qt)
bits per pixels.
The contents of the pixmap is uninitialized.
The depth can be either 1 (monochrome) or the depth of the
current video mode. If depth is negative, then the
hardware depth of the current video mode will be used.
If either width or height is zero, a null pixmap is
constructed.
See also isNull().
QPixmap::QPixmap ( const QSize & size, int depth = -1,
Optimization optimization = DefaultOptim )
This is an overloaded member function, provided for
convenience. It differs from the above function only in
what argument(s) it accepts.
QPixmap::~QPixmap ()
Destructs the pixmap.
bool QPixmap::convertFromImage ( const QImage & img, int
conversion_flags )
Converts an image and sets this pixmap. Returns TRUE if
successful.
The conversion_flags argument is a bitwise-OR from the
following choices. The options marked (default) are the
choice if no other choice from the list is included (they
are zero):
Color/Mono preference (ignored for QBitmap)
AutoColor (default) - If the image has depth 1 and
contains only black and white pixels, then the pixmap
becomes monochrome.
ColorOnly - The pixmap is dithered/converted to the native
display depth.
MonoOnly - The pixmap becomes monochrome. If necessary, it
is dithered using the chosen dithering algorithm.
Dithering mode preference, for RGB channels
DiffuseDither (default) - a high quality dither
OrderedDither - a faster more ordered dither
ThresholdDither - no dithering, closest color is used
Dithering mode preference, for alpha channel
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QPixmap(3qt)QPixmap(3qt)
DiffuseAlphaDither - a high quality dither
OrderedAlphaDither - a faster more ordered dither
ThresholdAlphaDither (default) - no dithering
Color matching versus dithering preference
PreferDither - always dither 32-bit images when the image
is being converted to 8-bits. This is the default when
converting to a pixmap.
AvoidDither - only dither 32-bit images if the image has
more than 256 colors and it is being converted to 8-bits.
This is the default when an image is converted for the
purpose of saving to a file.
Passing 0 for conversion_flags gives all the default
options.
Note that even though a QPixmap with depth 1 behaves much
like a QBitmap, isQBitmap() returns FALSE.
If a pixmap with depth 1 is painted with color0 and color1
and converted to an image, the pixels painted with color0
will produce pixel index 0 in the image and those painted
with color1 will produce pixel index 1.
See also convertToImage(), isQBitmap(),
QImage::convertDepth(), defaultDepth() and
QImage::hasAlphaBuffer().
Bugs and limitations:
Does not support 2 or 4 bit display hardware.
Examples: qtimage/qtimage.cpp
bool QPixmap::convertFromImage ( const QImage & image, ColorMode
mode=Auto )
This is an overloaded member function, provided for
convenience. It differs from the above function only in
what argument(s) it accepts.
QImage QPixmap::convertToImage () const
Converts the pixmap to an image. Returns a null image if
the operation failed.
If the pixmap has 1 bit depth, the returned image will
also be 1 bits deep. If the pixmap has 2-8 bit depth, the
returned image has 8 bit depth. If the pixmap has greater
than 8 bit depth, the returned image has 32 bit depth.
See also convertFromImage().
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Bugs and limitations:
Does not support 2 or 4 bit display hardware.
Alpha masks on monochrome images are ignored.
Examples: qmag/qmag.cpp
QBitmap QPixmap::createHeuristicMask ( bool clipTight = TRUE )
const
Creates and returns a heuristic mask for this pixmap. It
works by selecting a color from one of the corners, then
chipping away pixels of that color, starting at all the
edges.
The mask may not be perfect but should be reasonable, so
you can do things like:
pm->setMask( pm->createHeuristicMask() );
This function is slow because it involves transformation
to a QImage, non-trivial computations and a transformation
back to QBitmap.
See also QImage::createHeuristicMask().
int QPixmap::defaultDepth () [static]
Returns the default pixmap depth, i.e. the depth a pixmap
gets if -1 is specified.
See also depth().
QPixmap::Optimization QPixmap::defaultOptimization() [static]
Returns the default pixmap optimization setting.
See also setDefaultOptimization(), setOptimization() and
optimization().
int QPixmap::depth () const
Returns the depth of the image.
The pixmap depth is also called bits per pixel (bpp) or
bit planes of a pixmap. A null pixmap has depth 0.
See also defaultDepth(), isNull() and
QImage::convertDepth().
void QPixmap::detach () [virtual]
Special-purpose function that detaches the pixmap from
shared pixmap data.
A pixmap is automatically detached by Qt whenever its
contents is about to change. This is done in all QPixmap
member functions that modify the pixmap (fill(), resize(),
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QPixmap(3qt)QPixmap(3qt)convertFromImage(), load() etc.), in bitBlt() for the
destination pixmap and in QPainter::begin() on a pixmap.
It is possible to modify a pixmap without letting Qt know.
You can first obtain the system-dependent handle and then
call system-specific functions (for instance BitBlt under
Windows) that modifies the pixmap contents. In this case,
you can call detach() to cut the pixmap loose from other
pixmaps that share data with this one.
detach() returns immediately if there is just a single
reference or if the pixmap has not been initialized yet.
void QPixmap::fill ( const QColor & fillColor = Qt::white )
Fills the pixmap with the color fillColor.
void QPixmap::fill ( const QWidget * widget, const QPoint & ofs )
Fills the pixmap with the widget's background color or
pixmap. If the background is empty, nothing is done.
The ofs point is an offset in the widget.
The point ofs is a point in the widget's coordinate
system. The pixmap's top left pixel will be mapped to the
point ofs in the widget. This is significant if the widget
has a background pixmap, otherwise the pixmap will simply
be filled with the background color of the widget.
Example:
void CuteWidget::paintEvent( QPaintEvent *e )
{
QRect ur = e->rect(); // rectangle to update
QPixmap pix( ur.size() ); // Pixmap for double-buffering
pix.fill( this, ur.topLeft() ); // fill with widget background
QPainter p( &pix );
p.translate( -ur.x(), -ur.y() ); // use widget coordinate system
// when drawing on pixmap
// ... draw on pixmap ...
p.end();
bitBlt( this, ur.topLeft(), &pix );
}
Examples: grapher/grapher.cpp xform/xform.cpp
desktop/desktop.cpp
void QPixmap::fill ( const QWidget * widget, int xofs, int yofs )
This is an overloaded member function, provided for
convenience. It differs from the above function only in
what argument(s) it accepts.
QPixmap QPixmap::grabWidget ( QWidget * widget, int x=0, int y=0,
int w=-1, int h=-1 ) [static]
Creates a pixmap and paints widget in it.
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If widget has children, they are painted too,
appropriately located.
If you specify x, y, w or h, only the rectangle you
specify is painted. The defaults are 0, 0 (top-left
corner) and -1,-1 (which means the entire widget).
(If w is negative, the function copies everything to the
right border of the window. If h is negative, the function
copies everything to the bottom of the window.)
If widget is 0, or if the rectangle defined by x, y, the
modified w and the modified h does not overlap the
widget->rect(), this function returns a null QPixmap.
This function actually asks widget to paint itself (and
its children to paint themselves). QPixmap::grabWindow()
grabs pixels off the screen, which is a bit faster and
picks up exactly what's on-screen. This function works by
calling paintEvent() with painter redirection turned on,
which gets the result of paintEvent(), without e.g.
overlying windows.
If there is overlap, it returns a pixmap of the size you
want, containing a rendering of widget. If the rectangle
you ask for is a superset of widget, the area outside
widget are covered with the widget's background.
See also grabWindow(), QPainter::redirect() and
QWidget::paintEvent().
QPixmap QPixmap::grabWindow ( WId window, int x=0, int y=0, int
w=-1, int h=-1 ) [static]
Grabs the contents of a window and makes a pixmap out of
it. Returns the pixmap.
The arguments (x,y) specify the offset in the window,
while (w,h) specify the width and height of the area to be
copied.
If w is negative, the function copies everything to the
right border of the window. If h is negative, the function
copies everything to the bottom of the window.
Note that grabWindows() grabs pixels from the screen, not
from the window. This means that If there is another
window partially or entirely over the one you grab, you
get pixels from the overlying window too.
Note also that the mouse cursor is generally not grabbed.
The reason we use a window identifier and not a QWidget is
to enable grabbing of windows that are not part of the
application, window system frames, and so on.
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Warning: Grabbing an area outside the screen is not safe
in general. This depends on the underlying window system.
See also grabWidget().
int QPixmap::height () const
Returns the height of the pixmap.
See also width(), size() and rect().
Examples: qtimage/qtimage.cpp xform/xform.cpp
desktop/desktop.cpp scrollview/scrollview.cpp
movies/main.cpp
const char* QPixmap::imageFormat ( const QString & fileName )
[static]
Returns a string that specifies the image format of the
file fileName, or null if the file cannot be read or if
the format cannot be recognized.
The QImageIO documentation lists the supported image
formats.
See also load() and save().
bool QPixmap::isNull () const
Returns TRUE if it is a null pixmap.
A null pixmap has zero width, zero height and no contents.
You cannot draw in a null pixmap or bitBlt() anything to
it.
Resizing an existing pixmap to (0,0) makes a pixmap into a
null pixmap.
See also resize().
Examples: qmag/qmag.cpp scrollview/scrollview.cpp
bool QPixmap::isQBitmap () const
Returns TRUE if this is a QBitmap, otherwise FALSE.
bool QPixmap::load ( const QString & fileName, const char *
format, int conversion_flags )
Loads a pixmap from the file fileName. Returns TRUE if
successful, or FALSE if the pixmap could not be loaded.
If format is specified, the loader attempts to read the
pixmap using the specified format. If format is not
specified (default), the loader reads a few bytes from the
header to guess the file format.
See the convertFromImage() documentation for a description
of the conversion_flags argument.
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The QImageIO documentation lists the supported image
formats and explains how to add extra formats.
See also loadFromData(), save(), imageFormat(),
QImage::load() and QImageIO.
Examples: xform/xform.cpp scrollview/scrollview.cpp
picture/picture.cpp
bool QPixmap::load ( const QString & fileName, const char *
format=0, ColorMode mode=Auto )
This is an overloaded member function, provided for
convenience. It differs from the above function only in
what argument(s) it accepts.
bool QPixmap::loadFromData ( const uchar * buf, uint len, const
char * format, int conversion_flags )
Loads a pixmap from the binary data in buf (len bytes).
Returns TRUE if successful, or FALSE if the pixmap could
not be loaded.
If format is specified, the loader attempts to read the
pixmap using the specified format. If format is not
specified (default), the loader reads a few bytes from the
header to guess the file format.
See the convertFromImage() documentation for a description
of the conversion_flags argument.
The QImageIO documentation lists the supported image
formats and explains how to add extra formats.
See also load(), save(), imageFormat(),
QImage::loadFromData() and QImageIO.
bool QPixmap::loadFromData ( const QByteArray & buf, const char *
format=0, int conversion_flags=0 )
This is an overloaded member function, provided for
convenience. It differs from the above function only in
what argument(s) it accepts.
bool QPixmap::loadFromData ( const uchar * buf, uint len, const
char * format=0, ColorMode mode=Auto )
This is an overloaded member function, provided for
convenience. It differs from the above function only in
what argument(s) it accepts.
const QBitmap * QPixmap::mask () const
Returns the mask bitmap, or null if no mask has been set.
See also setMask() and QBitmap.
int QPixmap::metric ( int m ) const [virtual protected]
Internal implementation of the virtual
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QPixmap(3qt)QPixmap(3qt)QPaintDevice::metric() function.
Use the QPaintDeviceMetrics class instead.
Reimplemented from QPaintDevice.
QPixmap & QPixmap::operator= ( const QImage & image )
Converts the image image to a pixmap that is assigned to
this pixmap. Returns a reference to the pixmap.
See also convertFromImage().
QPixmap & QPixmap::operator= ( const QPixmap & pixmap )
Assigns the pixmap pixmap to this pixmap and returns a
reference to this pixmap.
QPixmap::Optimization QPixmap::optimization() const
Returns the optimization setting for this pixmap.
The default optimization setting is QPixmap::NormalOptim.
You may change this settings in two ways:
Call setDefaultOptimization() to set the default
optimization for all new pixmaps.
Call setOptimization() to set a the optimization for
individual pixmaps.
See also setOptimization(), setDefaultOptimization() and
defaultOptimization().
QRect QPixmap::rect () const
Returns the enclosing rectangle (0,0,width(),height()) of
the pixmap.
See also width(), height() and size().
Examples: xform/xform.cpp
void QPixmap::resize ( int w, int h )
Resizes the pixmap to w width and h height. If either w or
h is less than 1, the pixmap becomes a null pixmap.
If both w and h are greater than 0, a valid pixmap is
created. New pixels will be uninitialized (random) if the
pixmap is expanded.
Examples: grapher/grapher.cpp desktop/desktop.cpp
void QPixmap::resize ( const QSize & size )
This is an overloaded member function, provided for
convenience. It differs from the above function only in
what argument(s) it accepts.
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QPixmap(3qt)QPixmap(3qt)bool QPixmap::save ( const QString & fileName, const char *
format ) const
Saves the pixmap to the file fileName, using the image
file format format. Returns TRUE if successful, or FALSE
if the pixmap could not be saved.
See also load(), loadFromData(), imageFormat(),
QImage::save() and QImageIO.
Examples: qmag/qmag.cpp
bool QPixmap::save ( const QString & fileName, const char *
format, int quality ) const
Saves the pixmap to the file fileName, using the image
file format format and a quality factor quality. quality
must be in the range [0,100] or -1. Specify 0 to obtain
small compressed files, 100 for large uncompressed files
and -1 to use the default settings. Returns TRUE if
successful, or FALSE if the pixmap could not be saved.
See also load(), loadFromData(), imageFormat(),
QImage::save() and QImageIO.
bool QPixmap::selfMask () const
Returns TRUE if the pixmap's mask is identical to the
pixmap itself.
See also mask().
int QPixmap::serialNumber () const
Returns a number that uniquely identifies the contents of
this QPixmap object. This means that multiple QPixmaps
objects can have the same serial number as long as they
refer to the same contents. The serial number is for
example very useful for caching.
See also QPixmapCache.
void QPixmap::setDefaultOptimization ( Optimization optimization
) [static]
Sets the default pixmap optimization.
All new pixmaps that are created will use this default
optimization. You may also set optimization for individual
pixmaps using the setOptimization() function.
The initial default optimization setting is
QPixmap::Normal.
See also defaultOptimization(), setOptimization() and
optimization().
void QPixmap::setMask ( const QBitmap & newmask )
Sets a mask bitmap.
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The mask bitmap defines the clip mask for this pixmap.
Every pixel in mask corresponds to a pixel in this pixmap.
Pixel value 1 means opaque and pixel value 0 means
transparent. The mask must have the same size as this
pixmap.
Setting a null mask resets the mask,
See also mask(), createHeuristicMask() and QBitmap.
void QPixmap::setOptimization ( Optimization optimization )
Sets pixmap drawing optimization for this pixmap.
The optimization setting affects pixmap operations, in
particular drawing of transparent pixmaps (bitBlt() a
pixmap with a mask set) and pixmap transformations (the
xForm() function).
Pixmap optimization involves keeping intermediate results
in a cache buffer and use the data in the cache to speed
up bitBlt() and xForm(). The cost is more memory
consumption, up to twice as much as an unoptimized pixmap.
Use the setDefaultOptimization() to change the default
optimization for all new pixmaps.
See also optimization(), setDefaultOptimization() and
defaultOptimization().
Examples: desktop/desktop.cpp
QSize QPixmap::size () const
Returns the size of the pixmap.
See also width(), height() and rect().
Examples: qtimage/qtimage.cpp movies/main.cpp
QWMatrix QPixmap::trueMatrix ( const QWMatrix & matrix, int w,
int h ) [static]
Returns the actual matrix used for transforming a pixmap
with w width and h height.
When transforming a pixmap with xForm(), the
transformation matrix is internally adjusted to compensate
for unwanted translation, i.e. xForm() returns the
smallest pixmap containing all transformed points of the
original pixmap.
This function returns the modified matrix, which maps
points correctly from the original pixmap into the new
pixmap.
See also xForm() and QWMatrix.
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QPixmap(3qt)QPixmap(3qt)int QPixmap::width () const
Returns the width of the pixmap.
See also height(), size() and rect().
Examples: qtimage/qtimage.cpp xform/xform.cpp
desktop/desktop.cpp scrollview/scrollview.cpp
movies/main.cpp
QPixmap QPixmap::xForm ( const QWMatrix & matrix ) const
Returns a copy of the pixmap that is transformed using
matrix.
Qt uses this function to implement rotated text on window
systems that do not support such complex features.
Example of how to manually draw a rotated text at
(100,200) in a widget:
char *str = "Trolls R Qt"; // text to be drawn
QFont f( "Charter", 24 ); // use Charter 24pt font
QPixmap pm( 8, 8 );
QPainter p;
QRect r; // text bounding rectangle
QPoint bl; // text baseline position
p.begin( &pm ); // first get the bounding
p.setFont( f ); // text rectangle
r = p.fontMetrics().boundingRect(str);
bl = -r.topLeft(); // get baseline position
p.end();
pm.resize( r.size() ); // resize to fit the text
pm.fill( white ); // fills pm with white
p.begin( &pm ); // begin painting pm
p.setFont( f ); // set the font
p.setPen( blue ); // set blue text color
p.drawText( bl, str ); // draw the text
p.end(); // painting done
QWMatrix m; // transformation matrix
m.rotate( -33.4 ); // rotate coordinate system
QPixmap rp = pm.xForm( m ); // rp is rotated pixmap
QWMatrix t = QPixmap::trueMatrix( m, pm.width(), pm.height() );
int x, y;
t.map( bl.x(),bl.y(), &x,&y ); // get pm's baseline pos in rp
bitBlt( myWidget, 100-x, 200-y, // blt rp into a widget
&rp, 0, 0, -1, -1 );
This example outlines how Qt implements rotated text under
X11. The font calculation is the most tedious part. The
rotation itself is only 3 lines of code.
If you want to draw rotated text, you do not have to
implement all the code above. The code below does exactly
the same thing as the example above, except that it uses a
QPainter.
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QPixmap(3qt)QPixmap(3qt)
char *str = "Trolls R Qt"; // text to be drawn
QFont f( "Charter", 24 ); // use Charter 24pt font
QPainter p;
p.begin( myWidget );
p.translate( 100, 200 ); // translates coord system
p.rotate( -33.4 ); // rotates it counterclockwise
p.setFont( f );
p.drawText( 0, 0, str );
p.end();
See also trueMatrix(), QWMatrix and
QPainter::setWorldMatrix().
Bugs and limitations:
2 and 4 bits pixmaps are not supported.
Examples: qtimage/qtimage.cpp xform/xform.cpp
qmag/qmag.cpp desktop/desktop.cpp movies/main.cpp
RELATED FUNCTION DOCUMENTATIONQDataStream & operator>> (QDataStream & s, QPixmap & pixmap)
Reads a pixmap from the stream.
See also QPixmap::load() and Format of the QDataStream
operators
QDataStream & operator<;< (QDataStream & s, const QPixmap &
pixmap)
Writes a pixmap to the stream as a PNG image.
See also QPixmap::save() and Format of the QDataStream
operators
SEE ALSO
http://doc.trolltech.com/qpixmap.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2001 Trolltech AS,
http://www.trolltech.com. See the license file included
in the distribution for a complete license statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in
http://doc.trolltech.com/bughowto.html. Good bug reports
make our job much simpler. Thank you.
In case of content or formattting problems with this
manual page, please report them to qt-bugs@trolltech.com.
Please include the name of the manual page (qpixmap.3qt)
Trolltech AS 13 June 2001 17
QPixmap(3qt)QPixmap(3qt)
and the Qt version (2.3.1).
Trolltech AS 13 June 2001 18
