將文件轉換為字節數組

Question

我正在創建一個目錄，即文件，並將位圖圖像存儲到該文件中，現在如何將其轉換為字節數組

File myDir = new File(root + "/saved_images");      
                myDir.mkdirs();
                Random generator = new Random();
                int n = 10000;
                n = generator.nextInt(n);
                String fname = "Image-"+ n +".jpg";
                File file = new File (myDir, fname);

                if (file.exists ()) file.delete (); 
                try {
                    FileOutputStream out = new FileOutputStream(file);

                    bmp.compress(Bitmap.CompressFormat.JPEG, 90, out);

                    out.flush();
                    out.close();
                } catch (Exception e) {
                    e.printStackTrace();

                }

Answer 1

不確定要執行的操作，但可以嘗試執行以下操作：

InputStream is = ...
ByteArrayOutputStream buffer = new ByteArrayOutputStream();

int nRead;
byte[] data = new byte[some huge number, power of 2 preferably];

while ((nRead = is.read(data, 0, data.length)) != -1) {
  buffer.write(data, 0, nRead);
}

buffer.flush();

byte[] byteArray = buffer.toByteArray();

Answer 2

只需使用它來讀取您保存的文件。

// Returns the contents of the file in a byte array.
public static byte[] getBytesFromFile(File file) throws IOException {
    InputStream is = new FileInputStream(file);

    // Get the size of the file
    long length = file.length();

    // You cannot create an array using a long type.
    // It needs to be an int type.
    // Before converting to an int type, check
    // to ensure that file is not larger than Integer.MAX_VALUE.
    if (length > Integer.MAX_VALUE) {
        // File is too large
    }

    // Create the byte array to hold the data
    byte[] bytes = new byte[(int)length];

    // Read in the bytes
    int offset = 0;
    int numRead = 0;
    while (offset = 0) {
        offset += numRead;
    }

    // Ensure all the bytes have been read in
    if (offset

禮貌： http : //www.exampledepot.com

Answer 3

如果您只想修改現有代碼以將圖像寫入字節數組而不是文件中，請使用以下代碼替換try塊：

    ByteArrayOutputStream out = new ByteArrayOutputStream();
    bmp.compress(Bitmap.CompressFormat.JPEG, 90, out);
    bytes = out.getBytes();

...，其中bytes類型為byte[] ，並刪除生成文件名並刪除現有文件（如果存在）的代碼。 由於您正在寫入ByteArrayOutputStream，因此無需在out上調用flush()或close() 。 （他們什么也不會做。）

Answer 4

我已使用此代碼將圖像文件轉換為字節araay，

Bitmap bm = BitmapFactory.decodeResource(getResources(),R.drawable.abc);
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            bm.compress(Bitmap.CompressFormat.JPEG, 40 , bos);
            public byte[] bitmapdata = bos.toByteArray();
            Log.w("Image Conversion", String.valueOf(bitmapdata.length));
            String converted_txt="";
            for (int i = 0; i < bitmapdata.length; i++) 
           { 
               Log.w("Image Conversion", String.valueOf(bitmapdata[i]));
               ba = bitmapdata[i];
               converted_txt=converted_txt+bitmapdata[i]; 
           }
           try 
           {
               File myFile = new File("/sdcard/myImageToByteFile.jpg");
               myFile.createNewFile();
               fOut = new FileOutputStream(myFile);
               OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
               myOutWriter.write(ba);
               myOutWriter.close();
               fOut.close();
           }
           catch (Exception e) 
           {
               Toast.makeText(getApplicationContext(), e.getMessage(),5000).show();
           }