如何在Android中将位图保存到位图时设置dpi图像？

Question

我用这个功能来保存位图上的SD卡文件：

private static File storeImage(Context context, Bitmap image) { 
    File pictureFile = getOutputMediaFile(context); 
    if (pictureFile == null) { 
     return null; 
    } 
    try { 
     FileOutputStream fos = new FileOutputStream(pictureFile); 
     image.compress(Bitmap.CompressFormat.PNG, 100, fos); 
     fos.close(); 
    } catch (FileNotFoundException e) { 
     e.printStackTrace(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 

    return pictureFile; 
} 

private static File getOutputMediaFile(Context context){ 
    // To be safe, you should check that the SDCard is mounted 
    // using Environment.getExternalStorageState() before doing this. 
    File mediaStorageDir = new File(Environment.getExternalStorageDirectory() 
      + "/Android/data/" 
      + context.getPackageName() 
      + "/Files"); 

    // This location works best if you want the created images to be shared 
    // between applications and persist after your app has been uninstalled. 

    // Create the storage directory if it does not exist 
    if (! mediaStorageDir.exists()){ 
     if (! mediaStorageDir.mkdirs()){ 
      return null; 
     } 
    } 
    // Create a media file name 
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.ENGLISH).format(new Date()); 
    File mediaFile; 
    String mImageName="IMG_"+ timeStamp +".png"; 
    mediaFile = new File(mediaStorageDir.getPath() + File.separator + mImageName); 
    return mediaFile; 
} 

当我打开这个文件，看看图像DPI信息，它表明72个像素/英寸 like this

我如何可以设置它到300像素/英寸，或其他值？

Answer 1

以下是我用于管理截图和调整图像大小的一些辅助方法。

public static Bitmap getResizedBitmap(Bitmap bm, int newWidth, int newHeight, boolean recycleOriginal) { 
    int width = bm.getWidth(); 
    int height = bm.getHeight(); 

    // Determine scale to change size 
    float scaleWidth = ((float) newWidth)/width; 
    float scaleHeight = ((float) newHeight)/height; 

    // Create Matrix for maniuplating size 
    Matrix matrix = new Matrix(); 
    // Set the Resize Scale for the Matrix 
    matrix.postScale(scaleWidth, scaleHeight); 

    //Create a new Bitmap from original using matrix and new width/height 
    Bitmap resizedBitmap = Bitmap.createBitmap(bm, 0, 0, width, height, matrix, false); 

    //Remove memory leaks if told to recycle, warning, if using original else where do not recycle it here 
    if(recycleOriginal) { 
     bm.recycle(); 

    } 

    //Return the scaled new bitmap 
    return resizedBitmap; 

} 
public static Bitmap cropImage(Bitmap imgToCrop, int startX, int startY, int width, int height, boolean recycleOriginal){ 
    Bitmap croppedImage = Bitmap.createBitmap(imgToCrop, startX, startY , width , height); 

    if(recycleOriginal){ 
     imgToCrop.recycle(); 

    } 

    return croppedImage; 
} 
public static Bitmap takeScreenshotOfView(Activity context, Bitmap.CompressFormat compressFormat){ 
    Bitmap screenshot = null; 

    try { 
     // create bitmap screen capture 
     View v1 = context.getWindow().getDecorView().getRootView(); 
     v1.setDrawingCacheEnabled(true); 
     screenshot = Bitmap.createBitmap(v1.getDrawingCache()); 
     v1.setDrawingCacheEnabled(false); 

     File imageFile = new File(context.getFilesDir() + File.separator + "A35_temp" + File.separator + "screenshot_temp"); 

     FileOutputStream outputStream = new FileOutputStream(imageFile); 
     int quality = 100; 

     screenshot.compress(compressFormat, quality, outputStream); 
     outputStream.flush(); 
     outputStream.close(); 

    } catch (Throwable e) { 
     // Several error may come out with file handling or OOM 
     e.printStackTrace(); 
    } 

    return screenshot; 
} 

这些都是我ImageHelper课程的一部分一样，我只是用：

   Bitmap screenshot = ImageHelper.takeScreenshotOfView(this, Bitmap.CompressFormat.JPEG); 
      Bitmap croppedImage = ImageHelper.cropImage(screenshot, ImageHelper.mStartXCrop, ImageHelper.mStartYCrop, ImageHelper.mCropWidth, ImageHelper.mCropHeight, true); 
      returnImage = ImageHelper.getResizedBitmap(croppedImage, mCropImageWidth, mCropImageHeight, false); 

我不认为你正在尝试做的截图，但你仍然可以使用大小调整方法。

Answer 2

这些是我曾经DPI设置为位图同时节省，参阅here并且还here方法。

public void storeImage(Bitmap image) { 
     try { 
      File pictureFile = new File("yourpath"); 

      FileOutputStream fos = new FileOutputStream(pictureFile); 


      ByteArrayOutputStream imageByteArray = new ByteArrayOutputStream(); 
      image.compress(Bitmap.CompressFormat.JPEG, 100, imageByteArray); 
      byte[] imageData = imageByteArray.toByteArray(); 

      //300 will be the dpi of the bitmap 
      setDpi(imageData, 300); 

      fos.write(imageData); 
      fos.close(); 
     } catch (FileNotFoundException e) { 
      e.printStackTrace(); 
     } 
    } 


    public void setDpi(byte[] imageData, int dpi) { 
     imageData[13] = 1; 
     imageData[14] = (byte) (dpi >> 8); 
     imageData[15] = (byte) (dpi & 0xff); 
     imageData[16] = (byte) (dpi >> 8); 
     imageData[17] = (byte) (dpi & 0xff); 
    }