Picture

[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,

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