如何更改圖像的大小

Question

我正在從CameraCaptureTask獲取圖像，並且希望能夠在保存前使圖像變得更小。寬度和高度自動設置爲最高分辨率，這比我需要的多得多。我一直在嘗試獲取圖像，更改尺寸，然後嘗試保存，儘管我遇到了錯誤。

ORIGINAL

MainPage.xaml.cs中

private void cameraTask_Completed(object sender, PhotoResult e) 
    { 
     if (e.TaskResult == TaskResult.OK) 
     { 
      BitmapImage bmi = new BitmapImage(); 
      bmi.SetSource(e.ChosenPhoto); 
      //MessageBox.Show(bmi.PixelWidth.ToString() + "x" + bmi.PixelHeight.ToString()); 

      var gcd = GCD(bmi.PixelWidth, bmi.PixelHeight); 
      var result = string.Format("{0}:{1}", bmi.PixelWidth/gcd, bmi.PixelHeight/gcd); 

      WriteableBitmap wb; 
      Stream stream; 

      switch (result) 
      { 
       case "3:4": 
        wb = new WriteableBitmap(480,640); 
        break; 
       case "4:3": 
        wb = new WriteableBitmap(640,480); 
        break; 
       case "9:16": 
        wb = new WriteableBitmap(448, 800); 
        break; 
       case "16:9": 
        wb = new WriteableBitmap(800, 448); 
        break; 
       default: 
        wb = null; 
        return; 
      } 
      //Set the wb to the original stream? 
      wb.SetSource(e.ChosenPhoto); 

      //Convert the wb to a stream for saving 
      stream = new MemoryStream(wb.ToByteArray()); 

      //Need to replace the following line with the new image stream for saving? 
      //var capturedPicture = new CapturedPicture(e.OriginalFileName, e.ChosenPhoto); 
      var capturedPicture = new CapturedPicture(e.OriginalFileName, stream);   

     } 
    } 

    public int GCD(int a, int b) 
    { 
     while (a != 0 && b != 0) 
     { 
      if (a > b) 
       a %= b; 
      else 
       b %= a; 
     } 
     if (a == 0) 
      return b; 
     else 
      return a; 
    } 

編輯：新實現

private void cameraTask_Completed(object sender, PhotoResult e) 
    { 
     if (e.TaskResult == TaskResult.OK) 
     { 
      BitmapImage bmi = new BitmapImage(); 
      bmi.SetSource(e.ChosenPhoto); 

      var gcd = GCD(bmi.PixelWidth, bmi.PixelHeight); 
      var result = string.Format("{0}:{1}", bmi.PixelWidth/gcd, bmi.PixelHeight/gcd); 

      WriteableBitmap wb = new WriteableBitmap(bmi); 
      Stream stream = new MemoryStream(); 

      switch (result) 
      { 
       case "3:4": 
        wb.SaveJpeg(stream, 480, 640, 0, 100); 
        break; 
       case "4:3": 
        wb.SaveJpeg(stream, 640, 480, 0, 100); 
        break; 
       case "9:16": 
        wb.SaveJpeg(stream, 448, 800, 0, 100); 
        break; 
       case "16:9": 
        wb.SaveJpeg(stream, 800, 448, 0, 100); 
        break; 
       default: 
        wb = null; 
        return; 
      } 

      stream.Seek(0, SeekOrigin.Begin); 

      //var capturedPicture = new CapturedPicture(e.OriginalFileName, e.ChosenPhoto);     
      var capturedPicture = new CapturedPicture(e.OriginalFileName, stream); 

Answer 1

使用重載的位圖構造函數創建一個重新大小的圖像，你是唯一丟失是一個轉換回圖像數據類型：

public static Image resizeImage(Image imgToResize, Size size) 
{ 
    return (Image)(new Bitmap(imgToResize, size)); 
} 

yourImage = resizeImage(yourImage, new Size(50,50));