Android如何在不丟失質量的情況下縮小圖像大小

Question

我正在將圖像上傳到服務器。我想將圖像大小減小到200KB。如何在android中做到這一點。

Answer 1

您可以使用Bitmap.compress()方法來做到這一點。這裏是一個展示如何實現相同的樣本代碼：

代碼以縮放圖像的長寬比：

Bitmap bitmapImage = BitmapFactory.decodeFile("Your path"); 
int nh = (int) (bitmapImage.getHeight() * (512.0/bitmapImage.getWidth())); 
Bitmap scaled = Bitmap.createScaledBitmap(bitmapImage, 512, nh, true); 
your_imageview.setImageBitmap(scaled); 

壓縮圖像，而不在WhatsApp的損失質量，如：

public String compressImage(String imageUri) { 

     String filePath = getRealPathFromURI(imageUri); 
     Bitmap scaledBitmap = null; 

     BitmapFactory.Options options = new BitmapFactory.Options(); 

//  by setting this field as true, the actual bitmap pixels are not loaded in the memory. Just the bounds are loaded. If 
//  you try the use the bitmap here, you will get null. 
     options.inJustDecodeBounds = true; 
     Bitmap bmp = BitmapFactory.decodeFile(filePath, options); 

     int actualHeight = options.outHeight; 
     int actualWidth = options.outWidth; 

//  max Height and width values of the compressed image is taken as 816x612 

     float maxHeight = 816.0f; 
     float maxWidth = 612.0f; 
     float imgRatio = actualWidth/actualHeight; 
     float maxRatio = maxWidth/maxHeight; 

//  width and height values are set maintaining the aspect ratio of the image 

     if (actualHeight > maxHeight || actualWidth > maxWidth) { 
      if (imgRatio < maxRatio) { 
       imgRatio = maxHeight/actualHeight; 
       actualWidth = (int) (imgRatio * actualWidth); 
       actualHeight = (int) maxHeight; 
      } else if (imgRatio > maxRatio) { 
       imgRatio = maxWidth/actualWidth; 
       actualHeight = (int) (imgRatio * actualHeight); 
       actualWidth = (int) maxWidth; 
      } else { 
       actualHeight = (int) maxHeight; 
       actualWidth = (int) maxWidth; 

      } 
     } 

//  setting inSampleSize value allows to load a scaled down version of the original image 

     options.inSampleSize = calculateInSampleSize(options, actualWidth, actualHeight); 

//  inJustDecodeBounds set to false to load the actual bitmap 
     options.inJustDecodeBounds = false; 

//  this options allow android to claim the bitmap memory if it runs low on memory 
     options.inPurgeable = true; 
     options.inInputShareable = true; 
     options.inTempStorage = new byte[16 * 1024]; 

     try { 
//   load the bitmap from its path 
      bmp = BitmapFactory.decodeFile(filePath, options); 
     } catch (OutOfMemoryError exception) { 
      exception.printStackTrace(); 

     } 
     try { 
      scaledBitmap = Bitmap.createBitmap(actualWidth, actualHeight, Bitmap.Config.ARGB_8888); 
     } catch (OutOfMemoryError exception) { 
      exception.printStackTrace(); 
     } 

     float ratioX = actualWidth/(float) options.outWidth; 
     float ratioY = actualHeight/(float) options.outHeight; 
     float middleX = actualWidth/2.0f; 
     float middleY = actualHeight/2.0f; 

     Matrix scaleMatrix = new Matrix(); 
     scaleMatrix.setScale(ratioX, ratioY, middleX, middleY); 

     Canvas canvas = new Canvas(scaledBitmap); 
     canvas.setMatrix(scaleMatrix); 
     canvas.drawBitmap(bmp, middleX - bmp.getWidth()/2, middleY - bmp.getHeight()/2, new Paint(Paint.FILTER_BITMAP_FLAG)); 

//  check the rotation of the image and display it properly 
     ExifInterface exif; 
     try { 
      exif = new ExifInterface(filePath); 

      int orientation = exif.getAttributeInt(
        ExifInterface.TAG_ORIENTATION, 0); 
      Log.d("EXIF", "Exif: " + orientation); 
      Matrix matrix = new Matrix(); 
      if (orientation == 6) { 
       matrix.postRotate(90); 
       Log.d("EXIF", "Exif: " + orientation); 
      } else if (orientation == 3) { 
       matrix.postRotate(180); 
       Log.d("EXIF", "Exif: " + orientation); 
      } else if (orientation == 8) { 
       matrix.postRotate(270); 
       Log.d("EXIF", "Exif: " + orientation); 
      } 
      scaledBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0, 
        scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix, 
        true); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 

     FileOutputStream out = null; 
     String filename = getFilename(); 
     try { 
      out = new FileOutputStream(filename); 

//   write the compressed bitmap at the destination specified by filename. 
      scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 80, out); 

     } catch (FileNotFoundException e) { 
      e.printStackTrace(); 
     } 

     return filename; 

    } 

    public String getFilename() { 
     File file = new File(Environment.getExternalStorageDirectory().getPath(), "MyFolder/Images"); 
     if (!file.exists()) { 
      file.mkdirs(); 
     } 
     String uriSting = (file.getAbsolutePath() + "/" + System.currentTimeMillis() + ".jpg"); 
     return uriSting; 

    } 

    private String getRealPathFromURI(String contentURI) { 
     Uri contentUri = Uri.parse(contentURI); 
     Cursor cursor = getContentResolver().query(contentUri, null, null, null, null); 
     if (cursor == null) { 
      return contentUri.getPath(); 
     } else { 
      cursor.moveToFirst(); 
      int index = cursor.getColumnIndex(MediaStore.Images.ImageColumns.DATA); 
      return cursor.getString(index); 
     } 
    } 

    public int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) { 
     final int height = options.outHeight; 
     final int width = options.outWidth; 
     int inSampleSize = 1; 

     if (height > reqHeight || width > reqWidth) { 
      final int heightRatio = Math.round((float) height/(float) reqHeight); 
      final int widthRatio = Math.round((float) width/(float) reqWidth); 
      inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio; 
     } 
     final float totalPixels = width * height; 
     final float totalReqPixelsCap = reqWidth * reqHeight * 2; 
     while (totalPixels/(inSampleSize * inSampleSize) > totalReqPixelsCap) { 
      inSampleSize++; 
     } 

     return inSampleSize; 
    } 

另外，請檢查this one。和refer this一個以及服務器上傳，希望它有幫助！