Android — View如何轉存成Bitmap或是ARGB byte array raw file

如果你有需求將你畫面上的任何一個view轉成Bitmap，可以透過

public static Bitmap loadBitmapFromView(View v) {
    if(v == null){
        return null;
    }

    int h = v.getHeight();
    int w = v.getWidth();

    if(w <= 0 || h <= 0){
        return null;
    }

    Bitmap b = Bitmap.createBitmap( w, h, Bitmap.Config.ARGB_8888);
    Canvas c = new Canvas(b);
    v.layout(v.getLeft(), v.getTop(), v.getRight(), v.getBottom());
    v.draw(c);
    return b;
}

如果用kotlin可以改為extension function

private fun View.saveToBitmap(): Bitmap? {
    val h = height
    val w = width
    if (w <= 0 || h <= 0) {
        return null
    }
    return Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888).apply {
        val canvas = Canvas(this)
        layout(left, top, right, bottom)
        draw(canvas)
    }
}

接著如果你想要存下他的ByteArray資料

可以透過

private static void saveBitmapToFile(Context context,Bitmap bitmap){
    try {
        File filePath = new File(path,"test.jpg");
        if(filePath.exists()){
            return;
        }
        FileOutputStream fileOutputStream = new FileOutputStream(filePath);
        BufferedOutputStream bos = new BufferedOutputStream(fileOutputStream);
        int size = bitmap.getRowBytes() * bitmap.getHeight();
        ByteBuffer byteBuffer = ByteBuffer.allocate(size);
        bitmap.copyPixelsToBuffer(byteBuffer);
        bos.write(byteBuffer.array());
        bos.flush();
        bos.close();
        fileOutputStream.close();
    } catch (FileNotFoundException e) {
        //Log.w("TAG", "Error saving image file: " + e.getMessage());
    } catch (IOException e) {
        //Log.w("TAG", "Error saving image file: " + e.getMessage());
    }
}

或是你要存 jpeg or png 可以使用

private static void saveBitmapToFile(Context context,Bitmap bitmap){
    try {
        File filePath = new File(path,"test.jpg");
        if(filePath.exists()){
            return;
        }
        FileOutputStream fileOutputStream = new FileOutputStream(filePath);
        BufferedOutputStream bos = new BufferedOutputStream(fileOutputStream);
        bitmap.compress(Bitmap.CompressFormat.JPEG,90,fileOutputStream);            
        bos.flush();
        bos.close();
        fileOutputStream.close();
    } catch (FileNotFoundException e) {
        //Log.w("TAG", "Error saving image file: " + e.getMessage());
    } catch (IOException e) {
        //Log.w("TAG", "Error saving image file: " + e.getMessage());
    }
}

或是你單純要拿Bitmap的rawByteArray，透過kotlin可以寫成這樣

private fun Bitmap.getRawByteArray() = ByteBuffer.allocate(rowBytes * height).apply {
    copyPixelsToBuffer(this)
}.array()

就可以存成檔案。