qml更改相機圖像捕獲前的分辨率

Question

我想用特定分辨率捕捉圖像。 我使用了這段代碼，但從最後一個分辨率的相機捕獲的圖像和捕獲的圖像的分辨率不會更改爲大小（1280,720）。我想在捕捉圖像之前更改分辨率。

imageCapture { 
resolution: Qt.size(1280, 720) 
onImageCaptured: { 
photoPreview.source = preview 
} 

Answer 1

在很多情況下，QML Camera的行爲很奇怪，有些依賴關係還沒有很好的文檔記錄。

不管怎樣，下面的代碼對我的作品：

import QtQuick 2.6 
import QtQuick.Window 2.2 
import QtQuick.Layouts 1.3 
import QtQuick.Controls 1.4 
import QtMultimedia 5.6 

Window { 
    visible: true 

    width: 1280 
    height: 960 

    GridLayout { 
     id: grid 
     rows: 2 
     columns: 2 

     Item { 
      Layout.row: 0 
      Layout.column: 0 
      Layout.minimumWidth: 80 
      Layout.minimumHeight: 30 

      Button { 
       id: button 
       text: "capture" 
       onClicked: { 
        camera.stop(); 
        camera.viewfinder.resolution = "640x480"; 
        camera.start(); 
       } 
      } 
     } 

     Camera { 
      id: camera 
      captureMode: Camera.CaptureViewfinder 

      viewfinder.resolution: "160x120" 

      imageCapture { 
       id: cameracapture 

       onImageCaptured: { 
        photoPreview.source = preview // Show the preview in an Image 
        console.log("capture size: ", photoPreview.sourceSize); 
        timerHelper.restart(); 
       } 

      } 

      onCameraStateChanged: { 
       console.log("camera state changed to: ", cameraState); 
       if (cameraState == Camera.ActiveState && viewfinder.resolution == Qt.size(640,480)) { 
        cameracapture.capture(); 
       } 
      } 

      function cameraHelper() { 
       console.log("Stopping cam..."); 
       camera.stop(); 
       viewfinder.resolution = "160x120"; 
       camera.start(); 
      } 
     } 

     Timer { 
      id: timerHelper 
      interval: 1 
      onTriggered: camera.cameraHelper(); 
     } 

     Item { 
      width: 640 
      height: 480 

      Layout.row: 1 
      Layout.column: 0 
      Layout.minimumWidth: 640 
      Layout.minimumHeight: 480 

      Image { 

       width: 640 
       height: 480 

       id: photoPreview 
      } 
     } 

     Item { 
      width: 640 
      height: 480 

      Layout.row: 1 
      Layout.column: 1 
      Layout.minimumWidth: 640 
      Layout.minimumHeight: 480 

      VideoOutput { 
       source: camera 
       anchors.fill: parent 
       focus : visible // to receive focus and capture key events when visible 
      } 
     } 
    } 
} 

如果你想成功切換分辨率，你必須stop()和start()的Camera。

凍結，如果你嘗試切換分辨率回(160,120)在onImageCaptured，所以我用一個Timer獲得某種QueuedConnection。