Individual Pixel manipulation with QImage = Black Lines?

Hello all,

I'm working towards a more complex use for QImage and QPixmap, but for now I'm still trying to overcome this fundamental issue I see:

I am using this short code below with QT4 to show a Pixmap via a QLabel, but what I see is only half correct (see code and image below).

Code:

---

#include "widget.h"
#include "ui_widget.h"
 
#include <QPainter>
#include <QPaintDevice>
#include <QLabel>
#include <iostream>
#include <QImage>
#include <QPixmap>
 
using namespace std;
 
 
Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
 
 
    for(int i=0;i<100;i++)
    {
        for(int j=0;j<100;j++)
        {
 
 
            myimage =  QImage(100,100,QImage::Format_RGB32);
            QRgb colorval;
            colorval = qRgb(i,j,50);
 
            myimage.setPixel(j,i,colorval);
            cout << " Setting " << i << " " << j << endl;
 
 
 
        }
 
 
    }
 
 
 
 
    QPixmap mypixmap = QPixmap::fromImage(myimage);
    mylabel = new QLabel;
    mylabel->setPixmap(mypixmap);
    mylabel->setScaledContents(true);
    mylabel->show();
 
 
}
 
Widget::~Widget()
{
    delete ui;
}

---

From this code I expect each pixel to be colorized and not what actually occurs (See image):

Attachment 6560

Can anyone please explain to me the reason these black lines are present in my image?

If i and j are swapped, the lines become horizontal. Additionally, if a second loop is added with (i+1, j+1) the lines are covered.

Thank you,

You are reinitializing the image in every iteration of the loop. Are you sure this is what you want?

Taking that out of the loops solved the problem with the lines, thanks.