2 QPixmap to 1 QPixmap: Problem with invisible pixels

[Jerome96]

Hey guys!

I'm writing a function to put a QPixmap on an other QPixmap.
This works fine with this function:

@void AImage::addPixmap(int x, int y, QPixmap pixmap){
QImage pix = pixmap.toImage();
QImage image = tile_image->getPixmap().toImage();

int w = pix.width();
int h = pix.height();

float dX = 0;
float dY = 0;

for(int i = 0; i < image.width(); i++){
    for(int j = 0; j < image.height(); j++){
        if(i >= x && i <= x + w && j >= y && j <= y+h){
            if(QColor(pix.pixel(dX,dY)).){              // I want to check here if the pixel is invisible.. but how?
                image.setPixel(i,j,pix.pixel(dX,dY));
            }
            dY++;
        }
    }
    if(dY > 0){
        dX++;
    }
    dY = 0;
}

QPixmap outPut = QPixmap::fromImage(image);
tile_image->setPixmap(outPut);

}@

But how can I detect invisible pixels? I have a png file with some invisible pixels and don't want to put them on the background QPixmap.

I hope you can help me and sorry for my bad English :)

[Seba84]

I am not an expert on Image convertion but I found this on doc: "Alpha-Blended Drawing":http://qt-project.org/doc/qt-5/qcolor.html#alpha-blended-drawing

bq. QColor also support alpha-blended outlining and filling. The alpha channel of a color specifies the transparency effect, 0 represents a fully transparent color, while 255 represents a fully opaque color.

So I think your if-statement should be some thing like:
@if(QColor(pix.pixel(dX,dY)).alpha() < 255 )@

Hope it helps! :)

[Jerome96]

Thank you for the help :) but I tried this before. It won't work because every pixel of the image has an alpha of 255.

I hope we get this problem solved :)

[Seba84]

That means that the image is all opaque and there is no invisible or transparent pixels: for me invisible is equal to transparent with alpha = 0. Maybe this assumption is incorrect, and is the root-cause of your problem.

[Jerome96]

Yeah but there is a transparent background

http://s29.postimg.org/5w2ix3eib/shield.png(http://s29.postimg.org/5w2ix3eib/shield.png)

I uploaded the image. You have to save it then you will see there is a transparent background.

But thank you for your help :)

[raven-worx]

do you depend on this code? I mean there is a way easier method using QPainter:
@
void AImage::addPixmap(int x, int y, const QPixmap & pixmap)
{
QPixmap sourcePix = tile_image->getPixmap();

    QPainter p(sourcePix);
         p.drawPixmap( x, y, pixmap );
    p.end();

    tile_image->setPixmap(sourcePix);

}
@