[Solved] Drawing a new image from 2 images and check if it is black

icon444

Hey,

I'm pretty new to Qt and I've writting some code that must do this:

I have two images and I want to create a new image, the new image is a merge of the two. If image 1 has black then the new image will have on that spot blue color otherwise it should be from the original code.

This is my code but it doens't work.

@ int c, m, y, k, al;
QColor color;
QColor drawColor;
QImage background;
QImage world;
QSize sizeImage;
int height, width;

background.load("Background.jpg");
background = background.convertToFormat(QImage::Format_ARGB32);
QPainter painter(&world);
sizeImage = background.size();
width = sizeImage.width();
for(int i = 0; i < width; i++)
{
    color = QColor::fromRgb (background.pixel(50,50) );
    color.getCmyk(&c,&m,&y,&k,&al);

    if(c == 0 && m == 0 && y == 0 && k == 0) //then we have black as color and then we draw the color blue
    {
        drawColor.setBlue(255);
        painter.setPen(drawColor);
        painter.drawPoint(i,i);
    }
    else // then we draw from the background image
    {
        drawColor.setCmyk(c,m,y,k,al);
        painter.setPen(drawColor);
        painter.drawPoint(i,i);
    }

}

//adding new image to the graphicsScene
QGraphicsPixmapItem item( QPixmap::fromImage(world));
QGraphicsScene* scene = new QGraphicsScene;
scene->addItem(&item);

QGraphicsView view(scene);
view.show();

@

Is this a wrong way or what is wrong?

thanks already,

koahnig

welcome to devnet

You might want to check in the debugger, if all components for "black" pixels are at any time set to zero.

icon444

In my console I get this:

QPainter::setPen: Painter not active
QPainter::drawPoints: Painter not active

And what exactly do I need to check in the debugger?

EDIT: I've seen in the debugger nothing looks wrong I think. Why is the painter not drawning something? Also is my for lus correct? Or Do I need 2 for lussen because I don't know if QImage is 2D array or 1D array.

koahnig

Actually it is quite helpful to give us the error messages instead of just asking where is the problem ;-)

You construct a null image and then you try to write on it see "constructor":http://developer.qt.nokia.com/doc/qt-4.8/qimage.html#QImage
The application does not know where to write your pixel. Try to create QImage with a suitable size.

icon444

Solved thanks. That was the problem that it was a null image.