Printing adjecent images with alpha to pdf causes image edge overlap

#include <QApplication>
#include <QPrinter>
#include <QPainter>
#include <QImage>
#include <QString>

int main( int argc, char **argv )
{
    QApplication app( argc, argv );

    double dpi = 300.0;

    // Setup 8.5 x 11 inch printer
    //-------------------------------
    QPrinter *printer = new QPrinter( QPrinter::HighResolution );
    printer->setOutputFormat( QPrinter::PdfFormat );
    printer->setFullPage( true );
    printer->setOutputFileName( "kjg.pdf" );
    printer->setColorMode( QPrinter::Color );
    printer->setOrientation( QPrinter::Portrait );
    printer->setPaperSize( QSizeF( 8.5, 11 ), QPrinter::Inch );
    printer->setResolution( (int) dpi );


    // Setup 8.5 x 11 @ 300 dpi raster image.
    //-----------------------------------------
    QImage *outImg = new QImage( 2550, 3300, QImage::Format_ARGB32 );

    // Create out painters
    //----------------------
    QList<QPainter *> painters;
    painters.append( new QPainter( printer ) );
    painters.append( new QPainter( outImg ) );

    // Image to draw.
    //----------------
    int w = 100;
    int h = 1000;
    QImage *img = new QImage( w, h, QImage::Format_ARGB32 );
    img->fill( qRgba( 255, 0, 0, 128 ) );

    for( int j = 0; j < 2; j++ )
    {
        if( ! painters[j]->isActive() )
        {
            qDebug( "Painter not active." );
            delete outImg;
            delete printer;
            return( 0 );
        }

        painters[j]->setRenderHint( QPainter::Antialiasing );

        int x = 10;
        int y = 100;
        int prevX;

        for( int i = 0; i < 10; i++ )
        {
            if( i != 0 )
            {
                x = prevX + w;
                // Play with this value to see the different behavior.
//                x += 1;
            }

            prevX = x;
            painters[j]->drawImage( x, y, *img );
        }

        painters[j]->end();
    }

    outImg->save( "kjg.png", "PNG" );

    delete img;
    delete outImg;
    delete printer;

    return( 0 );
}