Picture

Payx

@jsulm ok thank you !

For calculate the color of each pixel, what function can i use?

jsulm

@Payx Do you mean to get the pixel value? http://doc.qt.io/qt-5/qimage.html#pixel-1
It returns http://doc.qt.io/qt-5/qcolor.html#QRgb-typedef containing the RGB values, then you can calculate what ever you need.
#AARRGGBB

quint32 rgb = static_cast<quint32>(image.pixel(x, y));
int blue = rgb & x000000FF;
int green = (rgb & 0x0000FF00)>>8;
int red = (rgb & 0x00FF0000)>>16;

kshegunov

@jsulm said in Picture:

quint32 rgb = static_cast<quint32>(image.pixel(x, y));
int blue = rgb & x000000FF;
int green = (rgb & 0x0000FF00)>>8;
int red = (rgb & 0x00FF0000)>>16;

There are the (inline) qRed(), qGreen() and qBlue() for that purpose, no need for bit-magic. :)

jsulm

@kshegunov Oh, good to know :-)

Payx

So can i use :

for (int i=0;i<pix.width()+1;i=i+4){
           for (int j=0;j<pix.height()+1;j=j+4){
               for(int x=0; x<i;x=x+1){
                  for (int z=0; z<j; z=z+1){
 QColor pixel = pix.pixelColor(x, z);

// i block here, can i use QColor [pixel] to create a tab and who will contain all my color ?

EDIT : i use a Qpixmap to display my picture, so i cant QImage pix; (the name of my picture is pix)

VRonin

These 2 should help you

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());
qint64 sumRed = 0;
qint64 sumGreen = 0;
qint64 sumBlue = 0;
for(int x=topLeft.x();x<maxRight;++x){
for(int y=topLeft.y();y<maxBottom;++y){
const QColor tempColor=image.pixelColor(x,y);
sumRed += tempColor.red();
sumGreen += tempColor.green();
sumBlue += tempColor.blue();
}
}
if(sumRed >= sumGreen  && sumRed >= sumBlue)
return Qt::red;
if(sumGreen  >= sumBlue)
return Qt::green;
return Qt::blue;
}

void fillSection(QImage& image,const QPoint& topLeft, const QSize& rectSize, const QColor& colour){
const int maxRight = qMin(image.width(),topLeft.x() + rectSize.width());
const int maxBottom = qMin(image.height(),topLeft.y() + rectSize.height());
for(int x=topLeft.x();x<maxRight;++x){
for(int y=topLeft.y();y<maxBottom;++y){
image.setPixelColor(x,y,colour);
}}
}

@Payx said in Picture:

i use a Qpixmap to display my picture, so i cant QImage pix; (the name of my picture is pix)

http://doc.qt.io/qt-5/qimage.html#details

Qt provides four classes for handling image data: QImage, QPixmap, QBitmap and QPicture. QImage is designed and optimized for I/O, and for direct pixel access and manipulation, while QPixmap is designed and optimized for showing images on screen. QBitmap is only a convenience class that inherits QPixmap, ensuring a depth of 1. Finally, the QPicture class is a paint device that records and replays QPainter commands.

Use QImage for pixel manipulation. you can use QImage::fromPixmap() and QPixmap::fromImage() to convert between the two

Payx

@VRonin Thanks for your answer, but thats very too complicated for me, and anyway i don't understand.

Can you explain your code ?

I tried something instead :

void MainWindow::on_push2_clicked()
{

	QRgb pix(int x, int z);
	int step=4;
	for (int i=0;i<pixi.width()+1;i=i+step){
		for (int j=0;j<pixi.height()+1;j=j+step){
			for(int x=0; x<i;x=x+1){
				for (int z=0; z<j; z=z+1){
					QRgb pixa = pixi.pixel(x, z);

the problem is here, how can i stock all the color of my square to after that compare them to know what is the dominant color


			}
	}
}
	}
}

VRonin

I simplified the code a bit.

The first function takes an image, the coordinates of the top left corner and the size of the rectangle (4x4 in your case) and tells you what is the dominant primary colour there

The second one takes an image, the coordinates of the top left corner and the size of the rectangle (4x4 in your case) and fills that rectangle with the colour in the argument

mrjj

@Payx
Hi, i added some comments. Its basically the same as what you tried , just broken up into good functions to produce clean code.

// this function , you give the image and the start and size of the current rect you are processing
QColor dominantColour(const QImage& image, const QPoint& topLeft, const QSize& rectSize) {
// calculate start stop values for the rect
   const int maxRight = qMin(image.width(), topLeft.x() + rectSize.width());
  const int maxBottom = qMin(image.height(), topLeft.y() + rectSize.height());
  QVector<QColor> coloursList; // this is a list of all colors seen!
  for(int x = topLeft.x(); x < maxRight; ++x) {
    for(int y = topLeft.y(); x < maxBottom; ++x) {
      coloursList << image.pixelColor(x, y); // store all colors seen in this Rect
    }
  }

  // these are functions that count (accumulate) how many times RED, GREEN and blue been used ( using the list from before)
  const qint64 sumRed = std::accumulate(coloursList.constBegin(), coloursList.constEnd(), 0, [](qint64 strt,  const QColor & val)->qint64 {return strt + val.red()});
  const qint64 sumGreen = std::accumulate(coloursList.constBegin(), coloursList.constEnd(), 0, [](qint64 strt, const QColor & val)->qint64 {return strt + val.green()});
  const qint64 sumBlue = std::accumulate(coloursList.constBegin(), coloursList.constEnd(), 0, [](qint64 strt, const QColor & val)->qint64 {return strt + val.blue()});
  // now we check out which is most used
  if(sumRed >= sumGreen  && sumRed >= sumBlue)
    return Qt::red;
  if(sumGreen  >= sumBlue)
    return Qt::green;
  return Qt::blue;
}

// this function can fill an rect with a color. So its used with dominantColour to actually replace the colors
void fillSection(QImage& image, const QPoint& topLeft, const QSize& rectSize, const QColor& colour) {
  // calculate start stop values for the rect
  const int maxRight = qMin(image.width(), topLeft.x() + rectSize.width());
  const int maxBottom = qMin(image.height(), topLeft.y() + rectSize.height());
  // go over all pixels in the rect
  for(int x = topLeft.x(); x < maxRight; ++x) {
    for(int y = topLeft.y(); x < maxBottom; ++x) {
      image.setPixelColor(x, y, colour); // replace color
    }
  }
}

Payx

Thanks for your help,

I got one error

undefined reference to 'MainWindow::dominantColor()'

VRonin

Payx

thats wasnt a simple letter that occured an error,

undefined reference to 'MainWindow::dominantColour()'
undefined reference to ''MainWindow::fillSection()'

SGaist

Because they are not part of MainWindow. Take a look again a the function signature.

Payx

@SGaist

Here my window.h

private slots:
	void on_push_clicked();
	QColor	dominantColour();
	void fillSection();

	void on_push2_clicked();

You said my function is not part of MainWindow, so i try to add MainWindow::

void MainWindow::fillSection(QImage& pixi, const QPoint& topLeft, const QSize& rectSize, const QColor& colour) {

and its said prototype for void Main...... does not match any in class 'MainWindow'

SGaist

Method signature mismatch.

Note: neither dominantColour nor fillSection make sense in the slots category.

kshegunov

@Payx said in Picture:

its said prototype for void Main...... does not match any in class 'MainWindow'

They don't match, the compiler's correct.

class MainWindow
{
    // ...
    void fillSection();
    // ...
};

in the header has different prototype from :

void MainWindow::fillSection(QImage& pixi, const QPoint& topLeft, const QSize& rectSize, const QColor& colour)
{
    // ...

in the source file. They must match, it's a requirement of the language.

Payx

So where am i suppose to declare my functions ?

jsulm

@Payx Again:

void fillSection()

is NOT the same as

void fillSection(QImage& pixi, const QPoint& topLeft, const QSize& rectSize, const QColor& colour)

So, either change void fillSection() to void fillSection(QImage& pixi, const QPoint& topLeft, const QSize& rectSize, const QColor& colour), or other way around. This is really basic C++.

Pradeep Kumar

Hi,

Function arguments must match otherwise u will get error.
Declare your functions in Header File, provide the definition in source file.
Use slots only when u want to get the values when signal is emitted providing the connect(); . Otherwise declare in any one of below specifiers.
add function in either of the access specifier depending upon your need

private:
void fillSection();

public:
void fillSection();

protected:
void fillSection();

The arguments which provided in declaration should match with the definition along with data type.

Thanks,

Payx

Thanks both of you, it works !
The problem i think is that i don't understand english very well, that's my problem.

So if i understood well,

i will have :

void MainWindow::on_push2_clicked()
{

	QColor dominantColor(const QImage& pixi, const QPoint& topLeft, const QSize& rectSize);
	void fillSection(QImage& pixi, const QPoint& topLeft, const QSize& rectSize, const QColor& colour);

}

I check what the code do, if i'm right i have to define the
rectSize.height()
and rectSize.width()

and last question
when i have

for(int x = topLeft.x(); x < maxRight; ++x) {
		for(int y = topLeft.y(); x < maxBottom; ++x) {

in the second line, it's not 'y' the variable who change?

and

const int maxRight = qMin(pixi.width(), topLeft.x() + rectSize.width());
for(int x = topLeft.x(); x < maxRight; ++x) {

if we define rectSize (4*4) the for will go from 0 to 4 only no ? we need to change the rectsize at the end of the for no ?