将位图转换为字节，反之亦然 [英] Converting bitmap to byte and vice versa

问题描述

我当前正在以位图格式从图库中读取图像.当将其保存到数据库中时，我需要将其转换为字节，而在Image Adapter类中，我需要将其转换为位图.

I am currently reading an image from gallery in Bitmap format. When saving it to the database I need to convert it into byte whilst in the Image Adapter class I need to convert it to bitmap.

以下是代码:-转换为字节以便将其存储在数据库中

The following is the code: - converting to byte in order to store it in database

 public void submitAction(View view)
    {
        /*This method creates a new post and populates it with the data added by the user. The data is then stored in the database
        * using the Active Android Library.*/
        Post p = new Post();
        EditText title = (EditText) findViewById(R.id.post_title_input);
        String tit = title.getText().toString();
        EditText description = (EditText)findViewById((R.id.editText));
        String desc = description.getText().toString();
        Bitmap img = yourSelectedImage;
        p.title=tit;
        p.description=desc;
        p.section="science";
        int bytes = img.getByteCount();
        ByteBuffer buffer = ByteBuffer.allocate(bytes); //Create a new buffer
        img.copyPixelsToBuffer(buffer);
        byte[] array = buffer.array();

   }

imageAdapter类中的代码-将byte []转换为Bitmap

Code in imageAdapter class - convert the byte[] to Bitmap

   public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if (convertView == null) {
            // if it's not recycled, initialize some attributes
            imageView = new ImageView(mContext);
            imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(8, 8, 8, 8);
        } else {
            imageView = (ImageView) convertView;
        }

        /*Converting image to byte*/
        Post p = posts.get(position);
        byte[] image = p.image;
        ByteArrayInputStream imageStream = new ByteArrayInputStream(image);
        Bitmap theImage = BitmapFactory.decodeStream(imageStream);
        imageView.setImageBitmap(theImage);
        return imageView;
    }

运行应用程序时，它在第Bitmap theImage = BitmapFactory.decodeStream(imageStream);行崩溃，并以空指针异常终止.

When runnning the application, it is crashing at line Bitmap theImage = BitmapFactory.decodeStream(imageStream); and terminates with a null pointer exception.

推荐答案

位图到字节[]

 Bitmap bitmap = ...;
 ByteArrayOutputStream stream = new ByteArrayOutputStream();
 bitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);
 byte[] byteArray = stream.toByteArray();

byte []到位图

 Bitmap bitmap = BitmapFactory.decodeByteArray(byteArray , 0, byteArray.length);

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