Picture

VRonin

shadowing

The case @kshegunov is explaining is in the 3rd code block of the link above:

// inner block scopes
#include <iostream>
using namespace std;

int main () {
  int x = 10;
  int y = 20;
  {
    int x;   // ok, inner scope.
    x = 50;  // sets value to inner x
    y = 50;  // sets value to (outer) y
    cout << "inner block:\n";
    cout << "x: " << x << '\n';
    cout << "y: " << y << '\n';
  }
  cout << "outer block:\n";
  cout << "x: " << x << '\n';
  cout << "y: " << y << '\n';
  return 0;
}

This means I should go back to that tutorial myself

Payx

@VRonin so if i want use my picture in an other function i have to declare it before my function as i did for

QColor dominantColor(const QImage& image, const QPoint& topLeft, const QSize& rectSize);

so i have to add a line code QImage pixi in my .cpp ?

why not in my .h, and why

QColor dominantColor

dont work in my .h too ?

VRonin

Ok, this has become too chatty, let's make it more structured before we both get banned.

Put dominantColor and fillSection code from either me or @mrjj at the top of your .cpp file, just below the #includes no need to declare them in advance in this case
in the private: section of your .h file add QImage m_baseImag;
in on_push_clicked load the image from file and store it in m_baseImag then use QPixmap::fromImage(m_baseImag) to display the image in the QLabel
in on_push2_clicked iterate over every 4x4 square of your picture calling the two functions:

for (int i=0;i<m_baseImag.width();i+=4){
           for (int j=0;j<m_baseImag.height();j+=4){
fillSection(m_baseImag,QPoint(i,j),QSize(4,4),dominantColour(m_baseImag,QPoint(i,j),QSize(4,4)));
}}

use QPixmap::fromImage(m_baseImag) to display the new image in another QLabel

Payx

Hello,

I have 0 error but it didn't work.

here my code

void MainWindow::on_push_clicked()
{
	QString fileName = QFileDialog::getOpenFileName(this,
	tr("Open Image"), "/", tr("Image Files (*.png *.jpg *.bmp)"));
	QPixmap pix(fileName);
	ui->label->setPixmap(pix);
	const QSize s = pix.size();
	QImage pixi = QImage(pix.toImage());

	

}

void MainWindow::on_push2_clicked()
{
	QPoint point(0,0);
	QSize size(4,4);
	for(int i=0;i<pixi.width();i+=4){
		for(int j=0;j<pixi.height();j+=4){
			fillSection(pixi,point,size,dominantColor(pixi,point,size));
		}
	}

	QPixmap pixa=QPixmap::fromImage(pixi);

	ui->label_2->setPixmap(pixa);
}

In my .h i declared

private:
   Ui::MainWindow *ui;
   QImage pixi;

pixi is the name of my picture (= m_baseImag)

i display pixa (Qpix from pixi) in the same label as pixi (dont know if i can do that)

mrjj

Hi
Good work.
in here
void MainWindow::on_push_clicked()
{
......
QImage pixi = QImage(pix.toImage()); // This looks like a local variable? ( die by scope)
}

Did you mean to use the one from .H ?

so
pixi = QImage(pix.toImage());

Payx

i changed my code by using pixi = QImage(pix.toImage());

and in my .h i got QImage pixi.

I try to fix my rectSize to 15x15

And my picture at the end is the same, she changed a little (she got a blue pixel in the top left

VRonin

you never update point in your loop. it's always 0,0 it should be i,j

Payx

This post is deleted!

Payx

Ok after long hours, i fixed it.

Thank you very much for your time in my project.

But i have a little question :

In the code it only returns Red, Blue or Green.

Do you have a function who return a lot of color, like if in my rect the most principal color is grey (for example) what could i do to add a lot of color ?

At the end i will have a picture more pixelated but that i can recognize

mrjj

Hi

if in my rect the most principal color is grey

That is just values for R,G,B. still.

VRonin

Modify dominantColour with this one. It takes the most frequent colour that appears in the square and fills it with it

QColor dominantColour(const QImage& image,const QPoint& topLeft, const QSize& rectSize){
	const int maxRight = qMin(image.width(),topLeft.x() + rectSize.width());
	const int maxBottom = qMin(image.height(),topLeft.y() + rectSize.height());
	QHash<QColor,int> colourMap;
	for(int x=topLeft.x();x<maxRight;++x){
		for(int y=topLeft.y();y<maxBottom;++y){
			const QColor tempColor=image.pixelColor(x,y);
			auto colourIter=colourMap.find(tempColor);
			if(colourIter==colourMap.end())
				colourMap.insert(tempColor,1);
			else
				colourIter.value()++;
		}
	}
	if(colourMap.isEmpty())
		return Qt::black;
	return std::max_element(colourMap.constBegin(),colourMap.constEnd()).key();
}

kshegunov

I suggest you average the color in the rectangle, e.g. (thanks to @VRonin for the scaffolding):

QColor dominantColour(const QImage & image,const QPoint & topLeft, const QSize & rectSize)
{
    qint32 averageRed = 0, averageGreen = 0, averageBlue = 0;

    const qint32 maxX = qMin<qint32>(image.width(), topLeft.x() + rectSize.width());
    const qint32 maxY = qMin<qint32>(image.height(), topLeft.y() + rectSize.height());
    for (qint32 y = topLeft.y(); y < maxY; y++)  {
        for (qint32 x = topLeft.x(); x < maxX; x++)   {
            QRgb pixel = image.pixel(x, y);
            
            averageRed += qRed(pixel);
            averageGreen += qGreen(pixel);
            averageBlue += qBlue(pixel);
        }
    }

    qint32 n = rectSize.width() * rectSize.height();

    Q_ASSERT(n);
    if (n <= 0)
        return Qt::black;

    return QColor(averageRed / n, averageGreen / n, averageBlue / n);
}

Payx

Thank you very much !