Qt应用程序中的高dpi缩放比例可平滑图标

Question

I have enabled high dpi support in my Qt application using QGuiApplication::setAttribute(Qt::AA_EnableHighDpiScaling); but now my images don't look crisp, instead they look "smoothed" out. For example below there is a picture of some button that are meant to be using high dpi images. When I disable the high dpi support and manually scale the ui, using the same images the icons are crisp and clear.

I have tried to set Qt::AA_UseHighDpiPixmaps with no success. Here is a sample code:

import QtQuick 2.11
import QtQuick.Window 2.11
import QtQuick.Controls 2.2

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    ToolButton{
        anchors.centerIn: parent
        icon.source: "qrc:/ic_star_white_48dp.png"
    }
}

The icon I am using is from Google material design icons and it is made for a high dpi screen device (resolution is 192x192). Enabling high dpi the icon in the toolbutton appears smoothed out. If I disable the high dpi support and set the height and width of the icon ( icon.height and icon.width ) to 640/160 * 48 ( 640 is the dpi of my device) the icon is crisp and clear. However, if I enable high dpi and set the height and width to 48 , the icon is not crisp.

Answer 1

I guess Qt's icon property scales images to increase performance (Eg the ToolButton is 48 x 48 the source image will be scaled to 48 x 48), but doesn't compensate for HighDpiScaling.

For example your ToolButton is scaled from 48 x 48 logical to 192 x 192 physical pixels by HighDpiScaling, but it is still using the downscaled 48 x 48 image.

I tend to use:

ToolButton{
anchors.centerIn: parent

    Image {
        anchors.centerIn: parent
        anchors.margins: 5
        //You can play around with those to balance quality and performance
        //mipmap: true
        //sourceSize.height: height * 2
        //sourceSize.width: width * 2
        fillMode: Image.PreserveAspectFit
        source: "qrc:/image.png"
    }
}