qpixmap.3qt

Qt/Embedded是一个多平台的C++图形用户界面应用程序框架

.TH QPixmap 3qt "10 November 2000" "Trolltech AS" \" -*- nroff -*-
.\" Copyright 1992-2000 Trolltech AS.  All rights reserved.  See the
.\" license file included in the distribution for a complete license
.\" statement.
.\"
.ad l
.nh
.SH NAME
QPixmap \- Off-screen pixel-based paint device
.SH SYNOPSIS
.br
.PP
\fC#include <qpixmap.h>\fR
.PP
Inherits QPaintDevice and Qt.
.PP
Inherited by QBitmap and QCanvasPixmap.
.PP
.SS "Public Members"
.in +1c
.ti -1c
.BI "enum \fBColorMode\fR { Auto, Color, Mono }"
.br
.ti -1c
.BI "enum \fBOptimization\fR { DefaultOptim, NoOptim, MemoryOptim=NoOptim, NormalOptim, BestOptim }"
.br
.ti -1c
.BI "\fBQPixmap\fR () "
.br
.ti -1c
.BI "\fBQPixmap\fR ( int " "w" ", int " "h" ", int " "depth" " = -1, Optimization = DefaultOptim ) "
.br
.ti -1c
.BI "\fBQPixmap\fR ( const QSize &, int " "depth" " = -1, Optimization = DefaultOptim ) "
.br
.ti -1c
.BI "\fBQPixmap\fR ( const QString & " "fileName" ", const char * " "format" "=0, ColorMode " "mode" "=Auto ) "
.br
.ti -1c
.BI "\fBQPixmap\fR ( const QString & " "fileName" ", const char * " "format" ", int conversion_flags ) "
.br
.ti -1c
.BI "\fBQPixmap\fR ( const char * xpm[] ) "
.br
.ti -1c
.BI "\fBQPixmap\fR ( const QByteArray & data ) "
.br
.ti -1c
.BI "\fBQPixmap\fR ( const QPixmap & ) "
.br
.ti -1c
.BI "\fB~QPixmap\fR () "
.br
.ti -1c
.BI "QPixmap& \fBoperator=\fR ( const QPixmap & ) "
.br
.ti -1c
.BI "QPixmap& \fBoperator=\fR ( const QImage & ) "
.br
.ti -1c
.BI "bool \fBisNull\fR () const"
.br
.ti -1c
.BI "int \fBwidth\fR () const"
.br
.ti -1c
.BI "int \fBheight\fR () const"
.br
.ti -1c
.BI "QSize \fBsize\fR () const"
.br
.ti -1c
.BI "QRect \fBrect\fR () const"
.br
.ti -1c
.BI "int \fBdepth\fR () const"
.br
.ti -1c
.BI "void \fBfill\fR ( const QColor & fillColor = Qt::white ) "
.br
.ti -1c
.BI "void \fBfill\fR ( const QWidget *, int " "xofs" ", int yofs ) "
.br
.ti -1c
.BI "void \fBfill\fR ( const QWidget *, const QPoint & ofs ) "
.br
.ti -1c
.BI "void \fBresize\fR ( int " "width" ", int height ) "
.br
.ti -1c
.BI "void \fBresize\fR ( const QSize & ) "
.br
.ti -1c
.BI "const QBitmap* \fBmask\fR () const"
.br
.ti -1c
.BI "void \fBsetMask\fR ( const QBitmap & ) "
.br
.ti -1c
.BI "bool \fBselfMask\fR () const"
.br
.ti -1c
.BI "QBitmap \fBcreateHeuristicMask\fR ( bool " "clipTight" " = TRUE ) const"
.br
.ti -1c
.BI "QPixmap \fBxForm\fR ( const QWMatrix & ) const"
.br
.ti -1c
.BI "QImage \fBconvertToImage\fR () const"
.br
.ti -1c
.BI "bool \fBconvertFromImage\fR ( const QImage &, ColorMode " "mode" "=Auto ) "
.br
.ti -1c
.BI "bool \fBconvertFromImage\fR ( const QImage &, int conversion_flags ) "
.br
.ti -1c
.BI "bool \fBload\fR ( const QString & " "fileName" ", const char * " "format" "=0, ColorMode " "mode" "=Auto ) "
.br
.ti -1c
.BI "bool \fBload\fR ( const QString & " "fileName" ", const char * " "format" ", int conversion_flags ) "
.br
.ti -1c
.BI "bool \fBloadFromData\fR ( const uchar * " "buf" ", uint " "len" ", const char * " "format" "=0, ColorMode " "mode" "=Auto ) "
.br
.ti -1c
.BI "bool \fBloadFromData\fR ( const uchar * " "buf" ", uint " "len" ", const char * " "format" ", int conversion_flags ) "
.br
.ti -1c
.BI "bool \fBloadFromData\fR ( const QByteArray & " "data" ", const char * " "format" "=0, int " "conversion_flags" "=0 ) "
.br
.ti -1c
.BI "bool \fBsave\fR ( const QString & " "fileName" ", const char * format ) const"
.br
.ti -1c
.BI "bool \fBsave\fR ( const QString & " "fileName" ", const char * " "format" ", int quality ) const"
.br
.ti -1c
.BI "int \fBserialNumber\fR () const"
.br
.ti -1c
.BI "Optimization \fBoptimization\fR () const"
.br
.ti -1c
.BI "void \fBsetOptimization\fR ( Optimization ) "
.br
.ti -1c
.BI "virtual void \fBdetach\fR () "
.br
.ti -1c
.BI "bool \fBisQBitmap\fR () const"
.br
.in -1c
.SS "Static Public Members"
.in +1c
.ti -1c
.BI "int \fBdefaultDepth\fR () "
.br
.ti -1c
.BI "QPixmap \fBgrabWindow\fR ( WId, int " "x" "=0, int " "y" "=0, int " "w" "=-1, int " "h" "=-1 ) "
.br
.ti -1c
.BI "QPixmap \fBgrabWidget\fR ( QWidget * " "widget" ", int " "x" "=0, int " "y" "=0, int " "w" "=-1, int " "h" "=-1 ) "
.br
.ti -1c
.BI "QWMatrix \fBtrueMatrix\fR ( const QWMatrix &, int " "w" ", int h ) "
.br
.ti -1c
.BI "const char* \fBimageFormat\fR ( const QString & fileName ) "
.br
.ti -1c
.BI "Optimization \fBdefaultOptimization\fR () "
.br
.ti -1c
.BI "void \fBsetDefaultOptimization\fR ( Optimization ) "
.br
.in -1c
.SS "Protected Members"
.in +1c
.ti -1c
.BI "\fBQPixmap\fR ( int " "w" ", int " "h" ", const uchar * " "data" ", bool isXbitmap ) "
.br
.ti -1c
.BI "virtual int \fBmetric\fR ( int ) const"
.br
.in -1c
.SH RELATED FUNCTION DOCUMENTATION
(Note that these are not member functions.)
.in +1c
.ti -1c
.BI "QDataStream & \fBoperator>>\fR (QDataStream & " "s" ", QPixmap & " "pixmap" ")"
.br
.ti -1c
.BI "QDataStream & \fBoperator<<\fR (QDataStream & " "s" ", const QPixmap & " "pixmap" ")"
.br
.in -1c
.SH DESCRIPTION
The QPixmap class is an off-screen pixel-based paint device.
.PP
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().
.PP
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 drawing, like this:
.IP 1
Create a pixmap with the same size as the widget.
.IP 2
Fill the pixmap with the widget background color.
.IP 3
Paint the pixmap.
.IP 4
bitBlt() the pixmap contents onto the widget.
.PP
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.
.PP
You can display a QPixmap on the screen easily using e.g. QLabel::setPixmap(), and all the QButton subclasses support pixmap use.
.PP
The QPixmap class uses lazy copying, so it is practical to pass pass QPixmap objects as arguments.
.PP
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.
.PP
Qt tries to work around the resource limitation. If you set the pixmap optimization to \fCQPixmap::MemoryOptim\fR 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.
.PP
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:
.PP
.nf
.br
    QPixmap::setDefaultOptimization( QPixmap::MemoryOptim );
.br
    while ( ... ) {
.br
      // load tool bar pixmaps etc.
.br
      QPixmap *pixmap = new QPixmap(fileName);
.br
    }
.br
    QPixmap::setDefaultOptimization( QPixmap::NormalOptim );
.fi
.PP
See also QBitmap, QImage, QImageIO and Shared Classes
.PP
Examples:
.(l
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
.)l
.SS "Member Type Documentation"
.SH "QPixmap::ColorMode"
This enum type defines the color modes that exist for converting QImage objects to QPixmap. The current values are: 
.TP
\fCAuto\fR - select \fCColor\fR or \fCMono\fR on a case-by-case basis.
.TP
\fCColor\fR - always create colored pixmaps.
.TP
\fCMono\fR - always create bitmaps.
.SH "QPixmap::Optimization"
QPixmap 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:
.TP
\fCDefaultOptim\fR - 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().
.TP
\fCNoOptim\fR - no optimization (currently the same as \fCMemoryOptim).\fR
.TP
\fCMemoryOptim\fR - optimize for minimal memory use.
.TP
\fCNormalOptim\fR - optimize for typical usage. Often uses more memory than \fCMemoryOptim,\fR and often faster.
.TP
\fCBestOptim\fR - optimize for pixmaps that are drawn very often and where performance is critical. Generally uses more memory than \fCNormalOptim\fR and may provide a little better speed.
.IP
.PP
We recommend sticking with \fCDefaultOptim\fR
.SH MEMBER FUNCTION DOCUMENTATION
.SH "QPixmap::QPixmap ()"
Constructs a null pixmap.
.PP