Pixmap transform: translate pixmap

I want to shift a pixmap by say 0.5 px to the right and then use it for a label. Unfortunately, pixmap.transformed returns a "convenient" result, that is inconvenient to me:
"Internally, the transformation matrix is adjusted to compensate for unwanted translation, i.e. transformed() returns the smallest pixmap containing all transformed points of the original pixmap."

How can I shift an image by .5 px to the right? shifting a label position by .5 px doesn't work either, so I'm a bit lost here. Would be nice if there's an easy solution, I'm rather new to Qt, but I hope it's no newbie question :-)

A pixel is the smallest addressable unit of the image, shifting by half a pixel either shifts by one pixel or by zero.

Cheers,
_

I guess you could create a new, slightly larger QImage. With a QPainter draw the old image after turning on anti-aliasing and translating using the QPointF version of the function. You might then get a different image that appears to have been shifted half a pixel.

Why you would bother given the size of pixels these days...

Ah, that lead to the solution, since draw doesn't accept subpixel either, I scaled up the png to 10*size, then I created a 10*larger image and pasted the huge image there, then I rescaled the image to 1/10. Thanks a lot!

Btw., I use the label as a marker, that's why I need subpixel precision.

Code:

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QPixmap pixmap("CrossI.png");
        QImage image(100,100,QImage::Format_ARGB32_Premultiplied);
        QPainter p;
        p.setRenderHint(QPainter::Antialiasing);
        QPoint shift;
 
        //for A
        image.fill(0);
 
        p.begin(&image);
        shift.setX((Ax-floor(Ax))*10);
        shift.setY((Ay-floor(Ay))*10);
        p.drawPixmap(shift,pixmap);
        p.end();
        pixmap = QPixmap::fromImage(image.scaledToWidth(10,Qt::SmoothTransformation),Qt::AutoColor);
        ui->label_5->setPixmap(pixmap);

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Quote:

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Originally Posted by DeepKling

Ah, that lead to the solution, since draw doesn't accept subpixel either

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No, but translate(QPointF point) does, and then you drawPixmap() at the (translated) origin. Not certain of the result but worth a try.

I would be interested in seeing the before/after images. While I'm sure you must have a valid reason for wanting to shift the image by 0.5 pixels, I'd love to see the visual difference of the result!