Superposition of two images

Zhitoune

Dear all,

I'm facing a problem in my soft, I'm superposing two image coming from a video stream :

            *leftImg = im.copy(0, 0, 512/2, 512);
            leftImg->setColorTable(redTable);
            *rightImg = im.copy( 256, 0, 512/2,  512);
            rightImg->setColorTable(greenTable);
            QPainter painter(dualViewImg);
            painter.drawImage(0, 0, *leftImg);
            painter.setCompositionMode(QPainter::CompositionMode_Overlay);
            painter.drawImage(0, 0, *rightImg);
            display->setPixmap(QPixmap::fromImage(dualViewImg->scaled(Xmaxi/2, Ymaxi)));

The superposition is working, but I would like to assign a spécific color to each image in order to make the comparison of the images easie. to do that I assign a red or green colortable to each image :

QVector<QRgb> redTable (256);
    QVector<QRgb> greenTable (256);
    for (int i = 0 ; i < 255; i++)
    {
        redTable[i] = qRgb(i, 0, 0);
        greenTable[i] = qRgb(0, i, 0);
    }

but it's not working the resulting image is still gray. What did I miss?
thanks in advance for your help.

ValentinMichelet

Hi,

Not sure if it's important, but your for loop will assign 255 values instead of 256.

QVector<QRgb> redTable (256);
QVector<QRgb> greenTable (256);
for (int i = 0 ; i < 256; i++)
{
    redTable[i] = qRgb(i, 0, 0);
    greenTable[i] = qRgb(0, i, 0);
}

That being said, I don't really understand what you are trying to achieve here.

Zhitoune

Sorry I didnot explain very well my problem. But it can be summed up to :
How do I transform a monochromatic QImage into a colored one?

mrjj

@Zhitoune said:

setColorTable

Are you sure it uses a color table?
Before you do ->setColorTable, what does
QImage::colorCount()
return?
For leftImg

Zhitoune

It returns 0. I have check my images format is RGB16.
there is always the options to rewritte a new image like this :

for (int i = 0 ; i <resX ; i++)
{
     for (int j = 0 ; j <resY ; j++)
     {
         newQImage.setPixel(i, j, qRgb (leftImg.pixel(i, j).red(), 0, 0)
     }
}
but I fear it to be too much time consuming..

mrjj

Well it seems not to use palette for that format.
So only option is to rewrite pixels as far I can see.
At least all samples do that.

chaiFF

I know that this post is pretty old but I think I found what is wrong! setColorTable only works for monochrome and 8-bit formats!! So the picture has to be transformed first :) I personally used
image->convertToFormat(QImage::Format_Indexed8,redTable) and It worked!!