QImage scaledtoHeight does not work for QImage::Format_Grayscale16

SachinBhat

Hi,

I wanted to scale the input image of format QImage::Format_Grayscale16. But the output image post transformation is garbage. Could anyone please provide a way to scale my images with the help of an inbuilt function?

Thanks
Sachin

SachinBhat

Hi,

I can provide more information if I am not clear with the problem?

The scaletoheight() uses transformation of images for scaling which I do not have any idea of implementation. I cannot convert the format to a format where the scaling is possible either. Or is there a way?

Thanks
Sachin

jsulm

@SachinBhat Please show your code where you scale the image...

SachinBhat

Hi,
@jsulm Thank you for your reply.

Below is the code snippet:

   QImage img("file_location");

#if IMG_DEBUG
    writer1.write(img);
#endif
    if (img.format() >= QImage::Format_RGBX64)
    {
        int width = DIV_ROUND(m_ptnWidth * PTN_IMG_HEIGHT, m_ptnHeight);
        delete m_ptnImageCache[cacheIndex].img;
        m_ptnImageCache[cacheIndex].img = new QImage(width, PTN_IMG_HEIGHT, QImage::Format_Grayscale16);
    }

    if(img.isNull())
        return NULL;

    int scaleHeight = DIV_ROUND(PTN_IMG_HEIGHT * img.height(),m_ptnHeight);

    scaledImage = img.scaledToHeight(scaleHeight);

I get improper output.

Left is the input, right is the output image

I get proper outputs for other formats

Thanks
Sachin

[Edit: Added code tags ~kshegunov]

kshegunov

It's possible this is a bug, seems that the pixel data alignment is broken for some reason. Could you prepare a very simple self-contained project (along with the test image) and upload it somewhere? Please strip the irrelevant code if you decide to do so (like the m_ptnImageCache).