Picture

[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,

1. Function arguments must match otherwise u will get error.
2. Declare your functions in Header File, provide the definition in source file.
3. 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.
4. 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 ?

[VRonin]

@Payx said in Picture:

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);

}

this makes no sense

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

yes, I corrected it but @mrjj was faster and copied the code before I could amend it

the for will go from 0 to 4 only no ?

no, it will go from 0 to 3, 4 pixels

[Payx]

@VRonin

no, it will go from 0 to 3, 4 pixels

Yes but if my picture is composed by 500 pixels, it will go from 0 to 3 pixels, and thats it, so i have to increase at the end of my "for" no ?

this makes no sense

When i want to call a function i have to write :

fillSection();

but as i said i got an error.

so i change to fillSection(QImage& pixi, const QPoint& topLeft, const QSize& rectSize, const QColor& colour);

why this makes no sense?

[VRonin]

@Payx said in Picture:

Yes but if my picture is composed by 500 pixels, it will go from 0 to 3 pixels, and thats it, so i have to increase at the end of my "for" no ?

what would you do?

@Payx said in Picture:

why this makes no sense?

www.cplusplus.com/doc/tutorial/functions/

www.cplusplus.com/doc/tutorial/classes/

[Payx]

@VRonin I got rectSize = 4*4

the function will calculate the color in the rect 44, if my picture is 500500, i have to increase at the end of my "for" the rectSize.

like say that my maxRight isnt

qMin(pixi.width(), topLeft.x() + rectSize.width());

anymore

and it's like qMin(pixi.width(), rectSize.width()+4)

and at the end of my for i will add a line to increase again and again the maxRight

[VRonin]

those to functions are designed to work on a single 4x4 area, you need to build something around them to make them work over the whole picture

[Payx]

Thanks for your link obviously what i need.

so i replace : i got

QColor dominantColor(pixi,point,size);

and i define pixi as my image (in mainwindow.h)
and QPoint point(0,0);
and QSize size(4,4); thats correct ?

but i block for the QColor in void fillSection(QImage& image, const QPoint& topLeft, const QSize& rectSize, const QColor& colour)

[kshegunov]

@VRonin said in Picture:

@Payx said in Picture:

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);
}

this makes no sense

It's valid C++, although highly unusual. Consider this:

void userFunction1()
{
    int x;
    testFunc(x);  //< Compile error: undeclared identifier testFunc
}

void userFunction2()
{
    void testFunc(int &);

    int x;
    testFunc(x); //< We are okay
}

void testFunc(int & z)
{
    z = 0;
}

C++ forbids function definitions to appear inside function bodies, but not declarations. On the other hand, class declarations and class definitions are valid inside functions, e.g.:

void terribleToReadFunction()
{
    struct  {
        int memberOfAnonymous() const
        {
            return 0;
        }
    } inst;

    int z = inst.memberOfAnonymous(); //< z is 0
}

[Payx]

@kshegunov
sorry i lost you

in my

void MainWindow::on_push2_clicked()
{
	QPoint point(0,0);
	QSize size(4,4);
	QColor dominantColor(pixi,point,size);

}

i try this i give what function needed and i declared point and size before

[mrjj]

@Payx said in Picture:
almost correct.

void MainWindow::on_push2_clicked()
{
QPoint point(0,0);
QSize size(4,4);
QColor domicolor=dominantColor(pixi,point,size); // where does pixi come from? its in .h?

}

[kshegunov]

@Payx said in Picture:

sorry i lost you

No, it's me who lost you. I was commenting on @VRonin's remark about your code. However, this:

QColor dominantColor(pixi,point,size);

is neither a function call, nor is it a function declaration. The compiler will interpret this as a variable and will throw "unknown conversion from type X to type Y" errors. You should carefully read @VRonin's link on functions - what is a declaration, what is a definition and how to put it all together. Otherwise you are in for a terrible time, Qt or otherwise.

Kind regards.

[Payx]

I have to declare my function,
say what they do
and call it.

I say in my .cpp what she does :

QColor dominantColor(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(); y < maxBottom; ++y) {
			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;
}

I call her and i stock the result in a QColor

void MainWindow::on_push2_clicked()
{
	QPoint point(0,0);
	QSize size(4,4);
	QColor domicolor=dominantColor(pixi,point,size);
// pixi is my image declared in .h with QImage pixi;

}

the problem that i dont know where i can declare her. I try every possibilities

[VRonin]

ok, now we are making progress. you got what the dominant colour is, now you have to paint the rectange

[Payx]

@VRonin said in Picture:

ok, now we are making progress. you got what the dominant colour is, now you have to paint the rectange

sorry if don't listen to you very well but

it say that my function isnt declared (dominantColor)

[VRonin]

http://www.cplusplus.com/doc/tutorial/functions/#declarations

[Payx]

Okay i fixed it

MainWindow::MainWindow(QWidget *parent) :
	QMainWindow(parent),
	ui(new Ui::MainWindow)
{
		ui->setupUi(this);

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

MainWindow::~MainWindow()
{
	delete ui;
}

So now with, fillSection, the problem i have is to declare something who correspond to QColor& colour

i check the code again, and i think its colourList no ?

[VRonin]

sorry if don't listen to you very well but

No worries, I'm explicitly refraining from giving you the exact answer and rather trying to send you on the right path.

i check the code again, and i think its colourList no ?

Nope, colourList will die: http://www.cplusplus.com/doc/tutorial/namespaces/#scopes