Main Page | Namespace List | Class Hierarchy | Alphabetical List | Class List | File List | Namespace Members | Class Members | File Members

QFrameBuffer Class Reference

This class serves as a frame buffer and event handler of a QLabel widget for displaying video frames.

It manages a QImage object as a frame buffer whose pixels may be set using the setPixel() method. For painting the frame buffer's contents into the QLabel widget's pixmap, a customEvent() handler is implemented.

Although this class is an extension of QWidget, it is not intended to be used as a replacement of the QLabel instance actually displaying the video frames. Actually, a QFrameBuffer widget will never become visible. . More...

#include <QFrameBuffer.hpp>

Inheritance diagram for QFrameBuffer:

VideoFrameBuffer List of all members.

Public Member Functions

 QFrameBuffer (QLabel *qlabel, int depth, int numColors=0, bool gray=true, QEvent::Type eventType=QEvent::User)
 Constructor.
virtual ~QFrameBuffer ()
 Destructor.
void setPixel (int x, int y, uint index_or_rgb)
 Set a pixel in the frame buffer.
void postPaintEvent ()
 Post a custom event for this object to display the frame buffer on the QLabel widget.

Protected Member Functions

virtual void customEvent (QCustomEvent *event)
 Event handler for displaying the QImage buffer's contents in the associated QLabel widget.

Detailed Description

This class serves as a frame buffer and event handler of a QLabel widget for displaying video frames.

It manages a QImage object as a frame buffer whose pixels may be set using the setPixel() method. For painting the frame buffer's contents into the QLabel widget's pixmap, a customEvent() handler is implemented.

Although this class is an extension of QWidget, it is not intended to be used as a replacement of the QLabel instance actually displaying the video frames. Actually, a QFrameBuffer widget will never become visible. .

Author:
Mario Taschwer
Version:
Id
QFrameBuffer.hpp,v 1.5 2005/02/22 18:26:11 mkropfbe Exp

Definition at line 75 of file QFrameBuffer.hpp.

Constructor & Destructor Documentation

QFrameBuffer::QFrameBuffer (  QLabel *  qlabel,
int  depth,
int  numColors = 0,
bool  gray = true,
QEvent::Type  eventType = QEvent::User
) 
 

Constructor.

Parameters:
qlabel the QLabel widget where to display the video frames. This object will become an invisible child of qlabel in the widget hierarchy. The frame buffer will be initialized to the width and height of qlabel.
depth the color depth of the frame buffer (8, 24, 32).
numColors the color table size of the frame buffer (if depth == 8).
gray if true and numColors > 0, set the color table entries to all gray values.
eventType the custom event type used by postPaintEvent() to request displaying the frame buffer on the qlabel widget. The value of this parameter should be in the range [QEvent::User, QEvent::MaxUser].
See also:
QImage::QImage(int, int, int, int, QImage::Endian)
Definition at line 59 of file QFrameBuffer.cpp.
00061   : QWidget(qlabel), VideoFrameBuffer(gray) {
00062 
00063   this->qlabel = qlabel;
00064   this->eventType = eventType;
00065   int real_depth = (depth == 24) ? 32 : depth;
00066   image = new QImage(qlabel->width(), qlabel->height(), real_depth, numColors);
00067   if (depth == 24)
00068     image->setAlphaBuffer(false);
00069   if (numColors > 0 && gray) {
00070     // initialize the color table to gray values
00071     int i;
00072     QRgb *ct = image->colorTable();
00073     for (i=0; i < numColors; i++)
00074       ct[i] = qRgb(i, i, i);
00075   }
00076   hide();                       // this widget should never be visible!
00077 }

Member Function Documentation

void QFrameBuffer::postPaintEvent (   )  [virtual]
 

Post a custom event for this object to display the frame buffer on the QLabel widget.

This is thread-safe and will cause the GUI thread to invoke customEvent(). We need to use custom events, as hidden widgets will not receive paint events.

Implements VideoFrameBuffer.

Definition at line 87 of file QFrameBuffer.cpp.

00088 {
00089   /* request repainting of qlabel without erasing it before */
00090   QApplication::postEvent(this, new QCustomEvent(eventType));
00091 }

void QFrameBuffer::setPixel (  int  x,
int  y,
uint  index_or_rgb
)  [inline, virtual]
 

Set a pixel in the frame buffer.

If this method is called from a thread other than the Qt GUI thread, the frame buffer should be locked before by calling the lock() method.

See also:
QImage::setPixel(int, int, uint)

Reimplemented from VideoFrameBuffer.

Definition at line 108 of file QFrameBuffer.hpp.

00108                                                         {
00109     image->setPixel(x, y, index_or_rgb);
00110   }

The documentation for this class was generated from the following files: