Block dots in image buttons

Thejas

I am running a Qt application in IMX6 board.
These are my platform details

Qt version = QtEmbedded 4.8
Application type = qml
Device = IMX6
I have a lot of buttons in my GUI, all are PNG files. The problem is some dark dots/lines are coming top of the icon.

But the same icons are working fine in qt-x11.
here is the side by side comparison

Qt-embedded - Lines in Image buttons
Qt-x11 - images and clean.

Here is the code snippet of the Close button

    ButtonImgItem
    {
        id                    : closeID
        objectName            : "CloseID"
        btnWidth              : Math.floor(Const.TYPEC_BUTTON_WIDTH   * Const.X_DPI)
        btnHeight             : Math.floor(Const.TYPEC_BUTTON_HEIGHT  * Const.Y_DPI)
        imagePath             : "../images/e_x_zone2b.png"
        btnTye                : ApplicationData.BUTTON_TYPE_C
        buttonState           : ApplicationData.BUTTON_STATE_NORMAL
        isCaligned            : true
        anchors.left          : parent.left
        anchors.leftMargin    : Const.HELP_SELECTGRID_LEFT_MARIGIN * Const.X_DPI
        anchors.bottom        : parent.bottom
        anchors.bottomMargin  : Const.HELP_SELECTGRID_BOTTOM_MARIGIN * Const.Y_DPI

        onSignalBtnClicked:
        {
            zone3itemID.enabled = false
            parent.enabled = false
        }

        onSignalSelectedState:
        {
            zone3itemID.enabled = true
            amIVisibile     = false
            parent.enabled  = true
            setBtnborderColor(Const.NORMAL_MODE_COLOR)
            state           = 'Normal'
            buttonState     = ApplicationData.BUTTON_STATE_NORMAL
            appDataController.saveVolume(parseInt(appDataController.getCurrentVolume())
                                                 , speakerCal
                                                 , 0
                                                 , appDataController.getCtrlSpeakerState())
            stopAudio()
            signalDismiss();
        }

    }

any idea why this is happening?