Get pixel color using WINAPI not working in QT-QML app?

[tanthinh1510]

Hi all!
I created example to get pixel color using WINAPI. When I get full screen, it's work fine
My source

#ifndef GETCOLOR_H
#define GETCOLOR_H
 
#include <QObject>
#include <QDebug>
#include <windows.h>
#include <QPoint>
#include <QString>
 
class getColor : public QObject
{
    Q_OBJECT
public:
    explicit getColor(QObject *parent = 0);
    Q_INVOKABLE void getMyPixel(int _x, int _y);
 
signals:
    void colorPixel(QString _color);
 
public slots:
    void posApplication(QPoint _pos);
    void posXApplication(int _posX);
    void posYApplication(int _posY);
private:
    int posX;
    int posY;
    QString colorR;
    QString colorG;
    QString colorB;
    QString colorsend;
 
 
};
 
#endif // GETCOLOR_H

#ifndef GETCOLOR_H
#define GETCOLOR_H

#include <QObject>
#include <QDebug>
#include <windows.h>
#include <QPoint>
#include <QString>

class getColor : public QObject
{
    Q_OBJECT
public:
    explicit getColor(QObject *parent = 0);
    Q_INVOKABLE void getMyPixel(int _x, int _y);

signals:
    void colorPixel(QString _color);

public slots:
    void posApplication(QPoint _pos);
    void posXApplication(int _posX);
    void posYApplication(int _posY);
private:
    int posX;
    int posY;
    QString colorR;
    QString colorG;
    QString colorB;
    QString colorsend;


};

#endif // GETCOLOR_H

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#include "getcolor.h"
 
getColor::getColor(QObject *parent) :
    QObject(parent)
{
    posX = posY = 0;
 
}
void getColor::getMyPixel(int _x, int _y)
{
//    HDC dc = GetDC(NULL);
    HDC dc = GetWindowDC(NULL);
    COLORREF color = GetPixel(dc, _x + posX, _y + posY);
 
    int _red = GetRValue(color);
    int _green = GetGValue(color);
    int _blue = GetBValue(color);
//    qDebug()<< "red"<< _red << "green"<<_green << "blue" << _blue;
    ReleaseDC(NULL, dc);
    colorR = QString::number( _red, 16 );
    if(colorR.length() == 1) {
        colorR.insert(0,"0");
    }
    colorG = QString::number( _green, 16 );
    if(colorG.length() == 1) {
        colorG.insert(0,"0");
    }
    colorB = QString::number( _blue, 16 );
    if(colorB.length() == 1) {
        colorB.insert(0,"0");
    }
    colorsend = "#";
    colorsend.append(colorR).append(colorG).append(colorB);
    emit colorPixel(colorsend);
}
 
void getColor::posApplication(QPoint _pos)
{
    posX = _pos.x();
    posY = _pos.y();
}
 
void getColor::posXApplication(int _posX)
{
    posX = _posX;
}
 
void getColor::posYApplication(int _posY)
{
    posY = _posY;
}

#include "getcolor.h"

getColor::getColor(QObject *parent) :
    QObject(parent)
{
    posX = posY = 0;

}
void getColor::getMyPixel(int _x, int _y)
{
//    HDC dc = GetDC(NULL);
    HDC dc = GetWindowDC(NULL);
    COLORREF color = GetPixel(dc, _x + posX, _y + posY);

    int _red = GetRValue(color);
    int _green = GetGValue(color);
    int _blue = GetBValue(color);
//    qDebug()<< "red"<< _red << "green"<<_green << "blue" << _blue;
    ReleaseDC(NULL, dc);
    colorR = QString::number( _red, 16 );
    if(colorR.length() == 1) {
        colorR.insert(0,"0");
    }
    colorG = QString::number( _green, 16 );
    if(colorG.length() == 1) {
        colorG.insert(0,"0");
    }
    colorB = QString::number( _blue, 16 );
    if(colorB.length() == 1) {
        colorB.insert(0,"0");
    }
    colorsend = "#";
    colorsend.append(colorR).append(colorG).append(colorB);
    emit colorPixel(colorsend);
}

void getColor::posApplication(QPoint _pos)
{
    posX = _pos.x();
    posY = _pos.y();
}

void getColor::posXApplication(int _posX)
{
    posX = _posX;
}

void getColor::posYApplication(int _posY)
{
    posY = _posY;
}

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#include <QApplication>
#include "qtquick2applicationviewer.h"
#include <QQmlApplicationEngine>
#include <QQmlApplicationEngine>
#include <QQmlEngine>
#include <QString>
#include <QQmlContext> // for setContextProperty
#include "getcolor.h"
#include "qwindow.h"
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    getColor m_getColor;
    QWindow m_window;
 
    QQmlApplicationEngine engine;
    QtQuick2ApplicationViewer viewer;
    viewer.setSource(QUrl("qrc:///main.qml"));
    viewer.rootContext()->setContextProperty("_getColor",&m_getColor);
    viewer.activeFocusItem();
    viewer.show();
 
    m_getColor.posApplication(viewer.position());
    QObject::connect(&viewer,SIGNAL(xChanged(int)),&m_getColor,SLOT(posXApplication(int)));
    QObject::connect(&viewer,SIGNAL(yChanged(int)),&m_getColor,SLOT(posYApplication(int)));
    return app.exec();
}

#include <QApplication>
#include "qtquick2applicationviewer.h"
#include <QQmlApplicationEngine>
#include <QQmlApplicationEngine>
#include <QQmlEngine>
#include <QString>
#include <QQmlContext> // for setContextProperty
#include "getcolor.h"
#include "qwindow.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    getColor m_getColor;
    QWindow m_window;

    QQmlApplicationEngine engine;
    QtQuick2ApplicationViewer viewer;
    viewer.setSource(QUrl("qrc:///main.qml"));
    viewer.rootContext()->setContextProperty("_getColor",&m_getColor);
    viewer.activeFocusItem();
    viewer.show();

    m_getColor.posApplication(viewer.position());
    QObject::connect(&viewer,SIGNAL(xChanged(int)),&m_getColor,SLOT(posXApplication(int)));
    QObject::connect(&viewer,SIGNAL(yChanged(int)),&m_getColor,SLOT(posYApplication(int)));
    return app.exec();
}

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import QtQuick 2.3
import QtQuick.Controls 1.2
 
Item {
    id: mainwindows
    visible: true
    width: 640
    height: 580
    property int r : 20
    property color colorPK: "white"
    Rectangle {
        width: 640
        height: 480
 
        gradient: Gradient {
            GradientStop {
                position: 0.0
                id: id1
                SequentialAnimation on color {
                    id: update1
                    loops: Animation.Infinite
                    ColorAnimation { from: "red"; to: "magenta"; duration: 1000 }
                    ColorAnimation { from: "magenta"; to: "blue"; duration: 1000 }
                    ColorAnimation { from: "blue"; to: "cyan"; duration: 1000 }
                    ColorAnimation { from: "cyan"; to: "lime"; duration: 1000 }
                    ColorAnimation { from: "lime"; to: "yellow"; duration: 1000 }
                    ColorAnimation { from: "yellow"; to: "red"; duration: 1000 }
                }
            }
            GradientStop {
                position: 1
                id: id2
                SequentialAnimation on color {
                    id: update2
                    loops: Animation.Infinite
                    ColorAnimation { from: "yellow"; to: "red"; duration: 1000 }
                    ColorAnimation { from: "red"; to: "magenta"; duration: 1000 }
                    ColorAnimation { from: "magenta"; to: "blue"; duration: 1000 }
                    ColorAnimation { from: "blue"; to: "cyan"; duration: 1000 }
                    ColorAnimation { from: "cyan"; to: "lime"; duration: 1000 }
                    ColorAnimation { from: "lime"; to: "yellow"; duration: 1000 }
                }
 
            }
        }
 
    }
    Rectangle {
        id: pickerCursor
        x: r; y: r
        width: r*2; height: r*2
        radius: r
        border.color: "black"; border.width: 2
        color: "transparent"
        Rectangle {
            anchors.fill: parent; anchors.margins: 2;
            border.color: "white"; border.width: 1
            radius: width/2
            color: "transparent"
        }
        MouseArea{
            anchors.fill: parent
            id: dragConsolWindowAreaa
            drag.target: parent
            drag.minimumX: 0
            drag.maximumX: mainwindows.width - pickerCursor.width
            drag.minimumY: 0
            drag.maximumY: mainwindows.height - pickerCursor.height
            onPositionChanged: {
 
            }
        }
    }
    Rectangle{
        id: colorReciver
        anchors.bottom: parent.bottom; anchors.bottomMargin:  0
        anchors.horizontalCenter: parent.horizontalCenter
        width: 100
        height: 100
        border.color: "black"
        color: colorPK
    }
 
    Connections{
        target: _getColor
        onColorPixel:{
           colorPK = _color
            console.log(_color)
        }
    }
 
    Timer{
        interval: 30
        repeat: true
        running: true
        onTriggered: {
            _getColor.getMyPixel(pickerCursor.x + pickerCursor.width / 2,pickerCursor.y + pickerCursor.height / 2)
        }
    }
}

import QtQuick 2.3
import QtQuick.Controls 1.2

Item {
    id: mainwindows
    visible: true
    width: 640
    height: 580
    property int r : 20
    property color colorPK: "white"
    Rectangle {
        width: 640
        height: 480

        gradient: Gradient {
            GradientStop {
                position: 0.0
                id: id1
                SequentialAnimation on color {
                    id: update1
                    loops: Animation.Infinite
                    ColorAnimation { from: "red"; to: "magenta"; duration: 1000 }
                    ColorAnimation { from: "magenta"; to: "blue"; duration: 1000 }
                    ColorAnimation { from: "blue"; to: "cyan"; duration: 1000 }
                    ColorAnimation { from: "cyan"; to: "lime"; duration: 1000 }
                    ColorAnimation { from: "lime"; to: "yellow"; duration: 1000 }
                    ColorAnimation { from: "yellow"; to: "red"; duration: 1000 }
                }
            }
            GradientStop {
                position: 1
                id: id2
                SequentialAnimation on color {
                    id: update2
                    loops: Animation.Infinite
                    ColorAnimation { from: "yellow"; to: "red"; duration: 1000 }
                    ColorAnimation { from: "red"; to: "magenta"; duration: 1000 }
                    ColorAnimation { from: "magenta"; to: "blue"; duration: 1000 }
                    ColorAnimation { from: "blue"; to: "cyan"; duration: 1000 }
                    ColorAnimation { from: "cyan"; to: "lime"; duration: 1000 }
                    ColorAnimation { from: "lime"; to: "yellow"; duration: 1000 }
                }

            }
        }

    }
    Rectangle {
        id: pickerCursor
        x: r; y: r
        width: r*2; height: r*2
        radius: r
        border.color: "black"; border.width: 2
        color: "transparent"
        Rectangle {
            anchors.fill: parent; anchors.margins: 2;
            border.color: "white"; border.width: 1
            radius: width/2
            color: "transparent"
        }
        MouseArea{
            anchors.fill: parent
            id: dragConsolWindowAreaa
            drag.target: parent
            drag.minimumX: 0
            drag.maximumX: mainwindows.width - pickerCursor.width
            drag.minimumY: 0
            drag.maximumY: mainwindows.height - pickerCursor.height
            onPositionChanged: {

            }
        }
    }
    Rectangle{
        id: colorReciver
        anchors.bottom: parent.bottom; anchors.bottomMargin:  0
        anchors.horizontalCenter: parent.horizontalCenter
        width: 100
        height: 100
        border.color: "black"
        color: colorPK
    }

    Connections{
        target: _getColor
        onColorPixel:{
           colorPK = _color
            console.log(_color)
        }
    }

    Timer{
        interval: 30
        repeat: true
        running: true
        onTriggered: {
            _getColor.getMyPixel(pickerCursor.x + pickerCursor.width / 2,pickerCursor.y + pickerCursor.height / 2)
        }
    }
}

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But when I get on QT-QML app, it's not work
code edit

#include "getcolor.h"
 
getColor::getColor(QObject *parent) :
    QObject(parent)
{
    posX = posY = 0;
 
}
void getColor::getMyPixel(int _x, int _y)
{
//    HDC dc = GetDC(NULL);
    HWND name = FindWindowA(0,"GetpixelColor");
    HDC dc = GetWindowDC(name);
    COLORREF color = GetPixel(dc, _x, _y);
 
    int _red = GetRValue(color);
    int _green = GetGValue(color);
    int _blue = GetBValue(color);
//    qDebug()<< "red"<< _red << "green"<<_green << "blue" << _blue;
    ReleaseDC(NULL, dc);
    colorR = QString::number( _red, 16 );
    if(colorR.length() == 1) {
        colorR.insert(0,"0");
    }
    colorG = QString::number( _green, 16 );
    if(colorG.length() == 1) {
        colorG.insert(0,"0");
    }
    colorB = QString::number( _blue, 16 );
    if(colorB.length() == 1) {
        colorB.insert(0,"0");
    }
    colorsend = "#";
    colorsend.append(colorR).append(colorG).append(colorB);
    emit colorPixel(colorsend);
}
 
void getColor::posApplication(QPoint _pos)
{
    posX = _pos.x();
    posY = _pos.y();
}
 
void getColor::posXApplication(int _posX)
{
    posX = _posX;
}
 
void getColor::posYApplication(int _posY)
{
    posY = _posY;
}

#include "getcolor.h"

getColor::getColor(QObject *parent) :
    QObject(parent)
{
    posX = posY = 0;

}
void getColor::getMyPixel(int _x, int _y)
{
//    HDC dc = GetDC(NULL);
    HWND name = FindWindowA(0,"GetpixelColor");
    HDC dc = GetWindowDC(name);
    COLORREF color = GetPixel(dc, _x, _y);

    int _red = GetRValue(color);
    int _green = GetGValue(color);
    int _blue = GetBValue(color);
//    qDebug()<< "red"<< _red << "green"<<_green << "blue" << _blue;
    ReleaseDC(NULL, dc);
    colorR = QString::number( _red, 16 );
    if(colorR.length() == 1) {
        colorR.insert(0,"0");
    }
    colorG = QString::number( _green, 16 );
    if(colorG.length() == 1) {
        colorG.insert(0,"0");
    }
    colorB = QString::number( _blue, 16 );
    if(colorB.length() == 1) {
        colorB.insert(0,"0");
    }
    colorsend = "#";
    colorsend.append(colorR).append(colorG).append(colorB);
    emit colorPixel(colorsend);
}

void getColor::posApplication(QPoint _pos)
{
    posX = _pos.x();
    posY = _pos.y();
}

void getColor::posXApplication(int _posX)
{
    posX = _posX;
}

void getColor::posYApplication(int _posY)
{
    posY = _posY;
}

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I try get color in another app, it's work very fine, but only do not work in QT - QML app. I don't know why?
Please help me to solve this problem.
Thank you for reading!
My project!
https://www.dropbox.com/s/554no9q9eg...Color.rar?dl=0

[anda_skoa]

Isn't the first application, which you say works, also a QtQuick application?

Cheers,
_

[tanthinh1510]

Hi anda_skoa!
when I get full screen to get color. It's work fine.

HDC dc = GetWindowDC(NULL);
COLORREF color = GetPixel(dc, _x + posX, _y + posY);

when I changed code, I do not work

HWND name = FindWindowA(0,"GetpixelColor");
HDC dc = GetWindowDC(name);
COLORREF color = GetPixel(dc, _x, _y);

After that I changed "GetpixelColor" by another applycation different QtQuick application . It work fine!. It only do not work with QtQuick application.

[wysota]

Does it work for other non-fullscreen OpenGL windows?

[anda_skoa]

Hi anda_skoa!
when I get full screen to get color. It's work fine.

when I changed code, I do not work

Then why change the code?

Have you tried using your working code and just translating the postions into global coordinates using QWindow::mapToGlobal()?

Cheers,
_

[tanthinh1510]

Hi wysota!
I don't know whether or not OpenGL windows. but I try QT-GUI and some app non-fullscreen, it's work.
It only do not work with QtQuick application.
How I can solve it?

---

Added after 5 minutes:

Hi anda_skoa!

Then why change the code?

because I only want get color inside app!

[wysota]

I don't know whether or not OpenGL windows.

So check that because QtQuick uses OpenGL for rendering.

[anda_skoa]

because I only want get color inside app!

Sure, that's where the position mapping comes in.
You have a point in your window, you map it to global coordinates and then use the code that is known to work with fullscreen coordinates.

Cheers,
_

[tanthinh1510]

Sure, that's where the position mapping comes in.
You have a point in your window, you map it to global coordinates and then use the code that is known to work with fullscreen coordinates.

Cheers,
_

When I get fullscreen and translating the postions to point I waint get. it's work fine
But have a problem when I minimize app or open another app overlaps my application.It's not working correct.
It's will get color of screen rather my app.

[anda_skoa]

Have you tried using the window's native handle instead of FindWindowA()?

Also, as wysota suggested twice, make sure your code works with non-fullscreen OpenGL windows in general.

Cheers,
_

[tanthinh1510]

Have you tried using the window's native handle instead of FindWindowA()?

Also, as wysota suggested twice, make sure your code works with non-fullscreen OpenGL windows in general.

Cheers,
_

Yes! I tried using the window's native handle instead of FindWindowA().
Code works with non-fullscreen window but not works with non-fullscreen OpenGL windows in general.
Maybe it's not support?

[wysota]

The code would have to read the color from your graphics card so I'm not suprised this doesn't work. What you could do is that you could render the scene to an FBO, download the texture as image and read the interesting pixel directly from the image using QImage::pixel().

[tanthinh1510]

So check that because QtQuick uses OpenGL for rendering.

If I build in Qt 5.0 and earlier, QtQuick uses OpenGL for rendering it?

[wysota]

Yes and no.

[tanthinh1510]

I build with MSVC2013 kit and it work OK Many thanks!