The example program on this page may be used, distributed and modified
without limitation.
Show Image
This example reads and displays an image in any supported image
format (GIF, BMP, PPM, XMP etc.)
#include "showimg.h"
#include <qmenubar.h>
#include <qfiledlg.h>
#include <qmsgbox.h>
#include <qpopmenu.h>
#include <qlabel.h>
#include <qpainter.h>
#include <qkeycode.h>
#include <qapp.h>
/*
In the constructor, we just pass the standard parameters on to
QWidget.
The menu uses a single slot to simplify the process of adding
more items to the options menu.
*/
ImageViewer::ImageViewer( QWidget *parent, const char *name )
: QWidget( parent, name ),
conversion_flags( PreferDither ),
filename( 0 ),
helpmsg( 0 )
{
pickx = -1;
menubar = new QMenuBar(this);
menubar->setSeparator( QMenuBar::InWindowsStyle );
QStrList fmt = QImage::outputFormats();
saveimage = new QPopupMenu();
savepixmap = new QPopupMenu();
for (const char* f = fmt.first(); f; f = fmt.next()) {
saveimage->insertItem( f );
savepixmap->insertItem( f );
}
connect( saveimage, SIGNAL(activated(int)), this, SLOT(saveImage(int)) );
connect( savepixmap, SIGNAL(activated(int)), this, SLOT(savePixmap(int)) );
file = new QPopupMenu();
menubar->insertItem( "&File", file );
file->insertItem( "Open...", this, SLOT(openFile()), CTRL+Key_O );
si = file->insertItem( "Save image", saveimage );
sp = file->insertItem( "Save pixmap", savepixmap );
file->insertSeparator();
file->insertItem( "Quit", qApp, SLOT(quit()), CTRL+Key_Q );
options = new QPopupMenu();
menubar->insertItem( "&Options", options );
ac = options->insertItem( "AutoColor" );
co = options->insertItem( "ColorOnly" );
mo = options->insertItem( "MonoOnly" );
options->insertSeparator();
fd = options->insertItem( "DiffuseDither" );
bd = options->insertItem( "OrderedDither" );
td = options->insertItem( "ThresholdDither" );
options->insertSeparator();
ta = options->insertItem( "ThresholdAlphaDither" );
ba = options->insertItem( "OrderedAlphaDither" );
fa = options->insertItem( "DiffuseAlphaDither" );
options->insertSeparator();
ad = options->insertItem( "PreferDither" );
dd = options->insertItem( "AvoidDither" );
options->setCheckable( TRUE );
setMenuItemFlags();
menubar->insertSeparator();
QPopupMenu* help = new QPopupMenu();
menubar->insertItem( "&Help", help );
help->insertItem( "Help!", this, SLOT(giveHelp()), CTRL+Key_H );
connect( options, SIGNAL(activated(int)), this, SLOT(doOption(int)) );
status = new QLabel(this);
status->setFrameStyle( QFrame::WinPanel | QFrame::Sunken );
status->setFixedHeight( fontMetrics().height() + 4 );
setMouseTracking( TRUE );
}
/*
This function modifies the conversion_flags when an options menu item
is selected, then ensures all menu items are up to date, and reconverts
the image if possibly necessary.
*/
void ImageViewer::doOption(int item)
{
if ( options->isItemChecked( item ) ) return; // They are all radio buttons
int ocf = conversion_flags;
if ( item == ac ) {
conversion_flags = conversion_flags & ~ColorMode_Mask | AutoColor;
} else if ( item == co ) {
conversion_flags = conversion_flags & ~ColorMode_Mask | ColorOnly;
} else if ( item == mo ) {
conversion_flags = conversion_flags & ~ColorMode_Mask | MonoOnly;
} else if ( item == fd ) {
conversion_flags = conversion_flags & ~Dither_Mask | DiffuseDither;
} else if ( item == bd ) {
conversion_flags = conversion_flags & ~Dither_Mask | OrderedDither;
} else if ( item == td ) {
conversion_flags = conversion_flags & ~Dither_Mask | ThresholdDither;
} else if ( item == ta ) {
conversion_flags = conversion_flags & ~AlphaDither_Mask | ThresholdAlphaDither;
} else if ( item == fa ) {
conversion_flags = conversion_flags & ~AlphaDither_Mask | DiffuseAlphaDither;
} else if ( item == ba ) {
conversion_flags = conversion_flags & ~AlphaDither_Mask | OrderedAlphaDither;
} else if ( item == ad ) {
conversion_flags = conversion_flags & ~DitherMode_Mask | PreferDither;
} else if ( item == dd ) {
conversion_flags = conversion_flags & ~DitherMode_Mask | AvoidDither;
}
if ( ocf != conversion_flags ) {
setMenuItemFlags();
// And reconvert...
reconvertImage();
repaint(); // show image in widget
}
}
/*
Set the options menu to reflect the conversion_flags value.
*/
void ImageViewer::setMenuItemFlags()
{
// File
bool valid_image = pm.size() != QSize( 0, 0 );
file->setItemEnabled( si, valid_image );
file->setItemEnabled( sp, valid_image );
// Options
bool may_need_color_dithering =
image.depth() == 32 && QPixmap::defaultDepth() <= 8;
bool may_need_dithering = may_need_color_dithering
|| image.depth() > 1 && options->isItemChecked(mo)
|| image.depth() > 1 && QPixmap::defaultDepth() == 1;
bool has_alpha_mask = image.hasAlphaBuffer();
options->setItemEnabled( fd, may_need_dithering );
options->setItemEnabled( bd, may_need_dithering );
options->setItemEnabled( td, may_need_dithering );
options->setItemEnabled( ta, has_alpha_mask );
options->setItemEnabled( fa, has_alpha_mask );
options->setItemEnabled( ba, has_alpha_mask );
options->setItemEnabled( ad, may_need_color_dithering );
options->setItemEnabled( dd, may_need_color_dithering );
options->setItemChecked( ac, (conversion_flags & ColorMode_Mask) == AutoColor );
options->setItemChecked( co, (conversion_flags & ColorMode_Mask) == ColorOnly );
options->setItemChecked( mo, (conversion_flags & ColorMode_Mask) == MonoOnly );
options->setItemChecked( fd, (conversion_flags & Dither_Mask) == DiffuseDither );
options->setItemChecked( bd, (conversion_flags & Dither_Mask) == OrderedDither );
options->setItemChecked( td, (conversion_flags & Dither_Mask) == ThresholdDither );
options->setItemChecked( ta, (conversion_flags & AlphaDither_Mask) == ThresholdAlphaDither );
options->setItemChecked( fa, (conversion_flags & AlphaDither_Mask) == DiffuseAlphaDither );
options->setItemChecked( ba, (conversion_flags & AlphaDither_Mask) == OrderedAlphaDither );
options->setItemChecked( ad, (conversion_flags & DitherMode_Mask) == PreferDither );
options->setItemChecked( dd, (conversion_flags & DitherMode_Mask) == AvoidDither );
}
void ImageViewer::updateStatus()
{
if ( pm.size() == QSize( 0, 0 ) ) {
if ( filename )
status->setText("Could not load image");
else
status->setText("No image - select Open from File menu.");
} else {
QString message, moremsg;
message.sprintf("%dx%d", image.width(), image.height());
if ( pm.size() != pmScaled.size() ) {
moremsg.sprintf(" [%dx%d]", pmScaled.width(),
pmScaled.height());
message += moremsg;
}
moremsg.sprintf(", %d bits ", image.depth());
message += moremsg;
if (image.valid(pickx,picky)) {
moremsg.sprintf("(%d,%d)=#%0*x ",
pickx, picky,
image.hasAlphaBuffer() ? 8 : 6,
image.pixel(pickx,picky));
message += moremsg;
}
if ( image.numColors() > 0 ) {
moremsg.sprintf(", %d colors", image.numColors());
message += moremsg;
}
if ( image.hasAlphaBuffer() ) {
if ( image.depth() == 8 ) {
int i;
bool alpha[256];
int nalpha=0;
for (i=0; i<256; i++)
alpha[i] = FALSE;
for (i=0; i<image.numColors(); i++) {
int alevel = image.color(i) >> 24;
if (!alpha[alevel]) {
alpha[alevel] = TRUE;
nalpha++;
}
}
moremsg.sprintf(", %d alpha levels", nalpha);
} else {
// Too many pixels to bother counting.
moremsg = ", 8-bit alpha channel";
}
message += moremsg;
}
status->setText(message);
}
}
/*
This function saves the image.
*/
void ImageViewer::saveImage( int item )
{
const char* fmt = saveimage->text(item);
QString savefilename = QFileDialog::getSaveFileName(0, 0, 0, filename);
if ( !savefilename.isEmpty() )
if ( !image.save( savefilename, fmt ) )
QMessageBox::warning( this, "Save failed", "Error saving file" );
}
/*
This function saves the converted image.
*/
void ImageViewer::savePixmap( int item )
{
const char* fmt = savepixmap->text(item);
QString savefilename = QFileDialog::getSaveFileName(0, 0, 0, filename);
if ( !savefilename.isEmpty() )
if ( !pmScaled.save( savefilename, fmt ) )
QMessageBox::warning( this, "Save failed", "Error saving file" );
}
/*
This function is the slot for processing the Open menu item.
*/
void ImageViewer::openFile()
{
QString newfilename = QFileDialog::getOpenFileName();
if ( !newfilename.isEmpty() ) {
loadImage( newfilename ) ;
repaint(); // show image in widget
}
}
/*
This function loads an image from a file and resizes the widget to
exactly fit the image size. If the file was not found or the image
format was unknown it will resize the widget to fit the errorText
message (see above) displayed in the current font.
Returns TRUE if the image was successfully loaded.
*/
bool ImageViewer::loadImage( const char *fileName )
{
filename = fileName;
bool ok = FALSE;
if ( filename ) {
QApplication::setOverrideCursor( waitCursor ); // this might take time
ok = image.load(filename, 0);
if ( ok )
ok = reconvertImage();
if ( ok ) {
setCaption( filename ); // set window caption
int w = pm.width();
int h = pm.height();
const int reasonable_width = 128;
if ( w < reasonable_width ) {
// Integer scale up to something reasonable
int multiply = ( reasonable_width + w - 1 ) / w;
w *= multiply;
h *= multiply;
}
h += menubar->heightForWidth(w) + status->height();
resize( w, h ); // we resize to fit image
} else {
pm.resize(0,0); // couldn't load image
update();
}
QApplication::restoreOverrideCursor(); // restore original cursor
}
updateStatus();
setMenuItemFlags();
return ok;
}
bool ImageViewer::reconvertImage()
{
bool success = FALSE;
QApplication::setOverrideCursor( waitCursor ); // this might take time
if ( pm.convertFromImage(image, conversion_flags) )
{
pmScaled = pm;
resize( width(), height() );
success = TRUE; // load successful
} else {
pm.resize(0,0); // couldn't load image
}
updateStatus();
setMenuItemFlags();
QApplication::restoreOverrideCursor(); // restore original cursor
return success; // TRUE if loaded OK
}
/*
This functions scales the pixmap in the member variable "pm" to fit the
widget size and puts the resulting pixmap in the member variable "pmScaled".
*/
void ImageViewer::scale()
{
int h = height() - menubar->heightForWidth( width() ) - status->height();
QApplication::setOverrideCursor( waitCursor ); // this might take time
if ( width() == pm.width() && h == pm.height() )
{ // no need to scale if widget
pmScaled = pm; // size equals pixmap size
} else {
QWMatrix m; // transformation matrix
m.scale(((double)width())/pm.width(), // define scale factors
((double)h)/pm.height());
pmScaled = pm.xForm( m ); // create scaled pixmap
}
QApplication::restoreOverrideCursor(); // restore original cursor
}
/*
The resize event handler, if a valid pixmap was loaded it will call
scale() to fit the pixmap to the new widget size.
*/
void ImageViewer::resizeEvent( QResizeEvent * )
{
status->setGeometry(0, height() - status->height(),
width(), status->height());
if ( pm.size() == QSize( 0, 0 ) ) // we couldn't load the image
return;
int h = height() - menubar->heightForWidth( width() ) - status->height();
if ( width() != pmScaled.width() || h != pmScaled.height())
{ // if new size,
scale(); // scale pmScaled to window
updateStatus();
}
}
/*
Record the pixel position of interest.
*/
void ImageViewer::mouseMoveEvent( QMouseEvent *e )
{
if ( pm.size() != QSize( 0, 0 ) ) {
int h = height() - menubar->heightForWidth( width() ) - status->height();
int npickx = e->x() * image.width() / width();
int npicky = (e->y()-menubar->heightForWidth( width() )) * image.height() / h;
if (npickx != pickx || npicky != picky ) {
pickx = npickx;
picky = npicky;
updateStatus();
}
}
}
/*
Draws the portion of the scaled pixmap that needs to be updated or prints
an error message if no legal pixmap has been loaded.
*/
void ImageViewer::paintEvent( QPaintEvent *e )
{
if ( pm.size() != QSize( 0, 0 ) ) { // is an image loaded?
QPainter painter(this);
painter.setClipRect(e->rect());
painter.drawPixmap(0, menubar->heightForWidth( width() ), pmScaled);
}
}
/*
Explain anything that might be confusing.
*/
void ImageViewer::giveHelp()
{
if (!helpmsg) {
QString helptext = "Usage: showimg [filename]";
QStrList support = QImage::inputFormats();
helptext += "\n\nSupported input formats:\n";
int lastnl = helptext.length();
helptext += " ";
const char* f = support.first();
helptext += f;
f = support.next();
for (; f; f = support.next()) {
helptext += ',';
if ( helptext.length() - lastnl > 40 ) {
helptext += "\n ";
lastnl = helptext.length() - 2;
} else {
helptext += ' ';
}
helptext += f;
}
helpmsg = new QMessageBox( "Help", helptext,
QMessageBox::Information, QMessageBox::Ok, 0, 0, 0, 0, FALSE );
}
helpmsg->show();
helpmsg->raise();
}
Generated at 17:19, 1997/09/30 for Qt version 1.30 by the webmaster at Troll Tech