[SOLVED] Cursor and image coordinates(problem with scaling)

[giesbert]

Hi Anticross,

Make x and y doubles

make m_scaleFactor a double with 1.0 = 100 %

make m_scaleFactor > 1.0 zoomed in and < 1.0 scaled out and use:

@
x *= m_scaleFactor;
y *= m_scaleFactor;
@

[Anticross]

I modified it and now it looks like this:
@void ImageWidget::mousePressEvent( QMouseEvent * event )
{
double x = event->pos().x();
double y = event->pos().y();

// Calculate scale and image sizes
double h = m_imageLabel->height();
double w = m_imageLabel->width();

if(x>w || y>h)
return;

if(h>size().height() || w>size().width())
{
m_scaleFactor = 1.0;
}

x *= m_scaleFactor;
y *= m_scaleFactor;

QRgb pixel = m_image.pixel(x,y);

QColor color = QColor::fromRgb(pixel);

}@ but I still have wrong coords(sometimes with some offset from right coords).

[Anticross]

The whole source of ImageViever class is
*.cpp:
@#include "ImageWidget.h"

//-----------------------------------------------------------------------------
ImageWidget::ImageWidget( QWidget * parent, const QString & filename ) : QWidget(parent)
{
m_imageLabel = new QLabel();
m_imageLabel->setBackgroundRole(QPalette::Base);
m_imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
m_imageLabel->setScaledContents(true);

m_scrollArea = new QScrollArea(this);
m_scrollArea->setBackgroundRole(QPalette::Dark);
m_scrollArea->setWidget(m_imageLabel);

QVBoxLayout * layout = new QVBoxLayout();
layout->addWidget(m_scrollArea);
setLayout(layout);

setWindowTitle(filename);
resize(500, 400);

// open file

m_image = QImage(filename);
if (m_image.isNull()) {
QMessageBox::information(this, tr("Warning"),
tr("Cannot load %1.").arg(filename));
return;
}

m_imageLabel->setPixmap(QPixmap::fromImage(m_image));

m_scaleFactor = 1.0;
normalSize();

m_pixelatorFlag = false;

//connect(parent->ui.actionPixelator, SIGNAL(triggered()), this, SLOT(pixelatorOn()));
}
//-----------------------------------------------------------------------------
void ImageWidget::zoomIn()
{

scaleImage(1.25);
}
//-----------------------------------------------------------------------------
void ImageWidget::zoomOut()
{
scaleImage(0.8);
}
//-----------------------------------------------------------------------------
void ImageWidget::normalSize()
{
m_imageLabel->adjustSize();
m_scaleFactor = 1.0;
}
//-----------------------------------------------------------------------------
void ImageWidget::fitToWindow( bool fitToWindow )
{
m_scrollArea->setWidgetResizable(fitToWindow);
if (!fitToWindow) {
normalSize();
}
}
//-----------------------------------------------------------------------------
void ImageWidget::scaleImage( double factor )
{
Q_ASSERT(m_imageLabel->pixmap());
m_scaleFactor *= factor;
m_imageLabel->resize(m_scaleFactor * m_imageLabel->pixmap()->size());

adjustScrollBar(m_scrollArea->horizontalScrollBar(), factor);
adjustScrollBar(m_scrollArea->verticalScrollBar(), factor);
}
//-----------------------------------------------------------------------------
void ImageWidget::adjustScrollBar( QScrollBar *scrollBar, double factor )
{
scrollBar->setValue(int(factor * scrollBar->value()

• ((factor - 1) * scrollBar->pageStep()/2)));
  }
  //-----------------------------------------------------------------------------
  void ImageWidget::mousePressEvent( QMouseEvent * event )
  {
  double x = event->pos().x();
  double y = event->pos().y();

// Calculate scale and image sizes
double h = m_imageLabel->height();
double w = m_imageLabel->width();

if(x>w || y>h)
return;

if(h>size().height() || w>size().width())
{
m_scaleFactor = 1.0;
}

x *= m_scaleFactor;
y *= m_scaleFactor;

QRgb pixel = m_image.pixel(x,y);

QColor color = QColor::fromRgb(pixel);

emit colorSelected(color.name(),x,y);

proccessImage(color,false);
}
//-----------------------------------------------------------------------------
void ImageWidget::proccessImage(QColor color, bool inverse)
{
// Search algorithm

QImage image = m_image;
int difference = 20;

for(int y = 0; y < image.height(); y++)
{
for(int x = 0; x < image.width(); x++)
{
QRgb currentPixel = image.pixel(x,y);

if( qAbs(qRed(currentPixel) - color.red()) > difference &&
qAbs(qGreen(currentPixel) - color.green()) > difference &&
qAbs(qBlue(currentPixel) - color.blue()) > difference)
{
if(!inverse)
image.setPixel(x,y,qRgb(255,255,255));
}
else
{
if(inverse)
image.setPixel(x,y,qRgb(255,255,255));
}
}
}
m_imageLabel->setPixmap(QPixmap::fromImage(image));
}
//-----------------------------------------------------------------------------
void ImageWidget::pixelatorOn()
{
// QAction * act = (QAction *)QObject::sender();
//
// if(act == NULL)
// return;
//
// if(act->isChecked())
// m_pixelatorFlag = true;
// else
// m_pixelatorFlag = false;
}
//-----------------------------------------------------------------------------
@
*.h:
@#ifndef IMAGEWIDGET_H
#define IMAGEWIDGET_H

#include <QWidget>
#include <QScrollBar>
#include <QScrollArea>
#include <QLabel>
#include <QMessageBox>
#include <QVBoxLayout>
#include <QMouseEvent>
#include <QColor>

class ImageWidget : public QWidget
{
Q_OBJECT

QLabel *m_imageLabel;
QScrollArea *m_scrollArea;
double m_scaleFactor;
QImage m_image;
bool m_pixelatorFlag;

public:
ImageWidget(QWidget * parent, const QString & filename);
void zoomIn();
void zoomOut();
void normalSize();
void fitToWindow(bool fitToWindow);

private:
void scaleImage(double factor);
void adjustScrollBar(QScrollBar *scrollBar, double factor);
void proccessImage(QColor color, bool inverse);

protected:
void mousePressEvent(QMouseEvent * event);

public slots:
void pixelatorOn();

signals:
void colorSelected(const QString & color, int x, int y);

};

#endif//IMAGEWIDGET_H
@

Maybe I miss something when editing qt example and thats why I get wrong coords ?

[giesbert]

You handle the mouse event with coordinates of teh ImageWidget class, but the picture is displayed in a subwidget. Map the coordinates to the label and it should work.

[Anticross]

I replace 84-85 rows of my cpp file by this:

@QPoint pos = m_imageLabel->mapFromParent(event->pos());
double x = pos.x();
double y = pos.y();@

And it's worked, thx Gerolf.

[Anticross]

Same trouble after some modificatin. When zoomOut and then make a click. Coordinates moved up left from real position, and after zoomOut its moved down right. Changed code looks like this:
*.h
@#ifndef IMAGEWIDGET_H
#define IMAGEWIDGET_H

#include <QWidget>
#include <QScrollBar>
#include <QScrollArea>
#include <QLabel>
#include <QMessageBox>
#include <QVBoxLayout>
#include <QMouseEvent>
#include <QColor>
#include <QGraphicsItem>

enum curAction {ePixel, eErase, eNoact};

class ImageWidget : public QWidget
{
Q_OBJECT

QLabel *m_imageLabel;
QScrollArea *m_scrollArea;
double m_scaleFactor;
QImage m_image;
bool m_pixelatorFlag;
int m_difference;
QColor m_currentColor;
curAction m_action;

public:
ImageWidget(QWidget * parent, const QString & filename);
void zoomIn();
void zoomOut();
void normalSize();
void fitToWindow(bool fitToWindow);
void setCurrentAction(curAction action);

private:
void scaleImage(double factor);
void adjustScrollBar(QScrollBar *scrollBar, double factor);
void proccessImage(QColor color, bool inverse);
void eraseImage(const QPointF & startPoint,const QPointF & endPoint);
void revertChanges();

protected:
void mousePressEvent(QMouseEvent * event);
void keyPressEvent (QKeyEvent * event);

public slots:
void onChangeDifference(int difference);

signals:
void colorSelected(const QString & color, int x, int y);

};

#endif//IMAGEWIDGET_H
@

[Anticross]

*.cpp
@#include "ImageWidget.h"

//-----------------------------------------------------------------------------
ImageWidget::ImageWidget( QWidget * parent, const QString & filename ) : QWidget(parent)
{
m_imageLabel = new QLabel();
m_imageLabel->setBackgroundRole(QPalette::Base);
m_imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
m_imageLabel->setScaledContents(true);

m_scrollArea = new QScrollArea(this);
m_scrollArea->setBackgroundRole(QPalette::Dark);
m_scrollArea->setWidget(m_imageLabel);

QVBoxLayout * layout = new QVBoxLayout();
layout->addWidget(m_scrollArea);
setLayout(layout);

setWindowTitle(filename);
resize(500, 400);

// open file

m_image = QImage(filename);
if (m_image.isNull()) {
QMessageBox::information(this, tr("Warning"),
tr("Cannot load %1.").arg(filename));
return;
}

m_imageLabel->setPixmap(QPixmap::fromImage(m_image));

m_scaleFactor = 1.0;
normalSize();

m_pixelatorFlag = false;

//connect(parent->ui.actionPixelator, SIGNAL(triggered()), this, SLOT(pixelatorOn()));

m_difference = 20;
m_currentColor = Qt::black;
}
//-----------------------------------------------------------------------------
void ImageWidget::zoomIn()
{

scaleImage(1.25);
}
//-----------------------------------------------------------------------------
void ImageWidget::zoomOut()
{
scaleImage(0.8);
}
//-----------------------------------------------------------------------------
void ImageWidget::normalSize()
{
m_imageLabel->adjustSize();
m_scaleFactor = 1.0;
}
//-----------------------------------------------------------------------------
void ImageWidget::fitToWindow( bool fitToWindow )
{
m_scrollArea->setWidgetResizable(fitToWindow);
if (!fitToWindow) {
normalSize();
}
}
//-----------------------------------------------------------------------------
void ImageWidget::scaleImage( double factor )
{
Q_ASSERT(m_imageLabel->pixmap());
m_scaleFactor *= factor;
m_imageLabel->resize(m_scaleFactor * m_imageLabel->pixmap()->size());

adjustScrollBar(m_scrollArea->horizontalScrollBar(), factor);
adjustScrollBar(m_scrollArea->verticalScrollBar(), factor);
}
//-----------------------------------------------------------------------------
void ImageWidget::adjustScrollBar( QScrollBar *scrollBar, double factor )
{
scrollBar->setValue(int(factor * scrollBar->value()

• ((factor - 1) * scrollBar->pageStep()/2)));
  }
  //-----------------------------------------------------------------------------
  void ImageWidget::mousePressEvent( QMouseEvent * event )
  {
  QPointF pos = m_imageLabel->mapFromParent(event->pos());

double x = pos.x();
double y = pos.y();

// Calculate scale and image sizes
double h = m_imageLabel->height();
double w = m_imageLabel->width();

if(x>w || y>h)
return;

if(h>size().height() || w>size().width())
{
m_scaleFactor = 1.0;
}

x *= m_scaleFactor;
y *= m_scaleFactor;

pos = QPointF(x,y);

QRgb pixel = m_image.pixel(x,y);

m_currentColor = QColor::fromRgb(pixel);

emit colorSelected(m_currentColor.name(),x,y);

switch (m_action)
{
case ePixel:
proccessImage(m_currentColor,false);
break;
case eErase:
eraseImage(pos, QPointF(pos.x()+50,pos.y()+50));
break;
case eNoact:
break;
}
}
//-----------------------------------------------------------------------------
void ImageWidget::keyPressEvent( QKeyEvent * event )
{
switch(event->key())
{
case Qt::Key_Z:
{
if(event->modifiers() == Qt::ControlModifier)
revertChanges();
}
break;
default:
QWidget::keyPressEvent(event);
}
}
//-----------------------------------------------------------------------------
void ImageWidget::proccessImage(QColor color, bool inverse)
{
// Search algorithm

QImage image = m_image;

for(int y = 0; y < image.height(); y++)
{
for(int x = 0; x < image.width(); x++)
{
QRgb currentPixel = image.pixel(x,y);

if( qAbs(qRed(currentPixel) - color.red()) > m_difference &&
qAbs(qGreen(currentPixel) - color.green()) > m_difference &&
qAbs(qBlue(currentPixel) - color.blue()) > m_difference)
{
if(!inverse)
image.setPixel(x,y,qRgb(255,255,255));
}
else
{
if(inverse)
image.setPixel(x,y,qRgb(255,255,255));
}
}
}
m_imageLabel->setPixmap(QPixmap::fromImage(image));

// QMessageBox::information(this, tr("Done"),
// tr("Processing image done.n"
// "The document has been modified."),
// QMessageBox::Ok);
}
//-----------------------------------------------------------------------------
void ImageWidget::eraseImage( const QPointF & startPoint,const QPointF & endPoint )
{
QImage image = m_image;

for(int y = 0; y < image.height(); y++)
for(int x = 0; x < image.width(); x++)
if(y > startPoint.y() && y < endPoint.y())
if(x > startPoint.x() && x<endPoint.x())
image.setPixel(x,y,qRgb(255,255,255));

m_imageLabel->setPixmap(QPixmap::fromImage(image));

m_image = image;
}
//-----------------------------------------------------------------------------
void ImageWidget::revertChanges()
{
QImage image = m_imageLabel->pixmap()->toImage();

m_imageLabel->setPixmap(QPixmap::fromImage(m_image));

m_image = image;
}
//-----------------------------------------------------------------------------
void ImageWidget::onChangeDifference(int difference)
{
m_difference = difference;
//proccessImage(m_currentColor,false);
}
//-----------------------------------------------------------------------------
void ImageWidget::setCurrentAction( curAction action )
{
m_action = action;
}
//-----------------------------------------------------------------------------
@

[Anticross]

I done this:
make m_scalefactor double;
When zoom in 0,8;
when zoom out 1,25;

if(h>size().height() || w>size().width())
{
m_scaleFactor = 1.0;
}

But I still have wrong coords in mouse press event x and y if I already make zomming, without zumming it's work correct. Please check somebody my code and make some corrections or recommendations.

[mahdhaoui]

Hello, i'am Novice in Qt program. I'am interested for you program (extention of imageViewer).
Can you post it if you have the solution. Thank you.

[Anticross]

I post header and source file of my Image widget class before. So you can see it, mahdhaoui. You just need to make an empty qt solution and use my class :)