捕获的图像分辨率太大

Question

我在做什么？

我允许用户捕获图像，将其存储到 SD 卡中并上传到服务器。

但是将捕获的图像的分辨率设置为宽度：4608 像素和高度：2592 像素

现在我想要什么？

如何在不影响质量的情况下获得小分辨率图像，例如我可以获得的最小分辨率或将捕获的图像分辨率设置为原始图像分辨率的 25%..（特定于设备）

CameraCaptureActivity.java：

public class CameraCaptureActivity extends Activity implements OnClickListener, PictureCallback {

    CameraSurfaceView cameraSurfaceView;
    Button shutterButton;
    SimpleDateFormat simpleDateFormat;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_camera_capture);

        FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
        cameraSurfaceView = new CameraSurfaceView(this);
        preview.addView(cameraSurfaceView);

        shutterButton = (Button) findViewById(R.id.shutter_button);
        shutterButton.setOnClickListener(this);
    }


    @Override
    public void onClick(View v) {
        takePicture();
    }

    private void takePicture() {
        shutterButton.setEnabled(false);
        cameraSurfaceView.takePicture(this);
    }

    @Override
    public void onPictureTaken(byte[] data, Camera camera) {
        // TODO something with the image data

        File pictureFileDir = getDir();

        if (!pictureFileDir.exists() && !pictureFileDir.mkdirs()) {
            return;
        }


        simpleDateFormat = new SimpleDateFormat("yyyyMMddHHmmss");
        strDateFormat = simpleDateFormat.format(new Date());

        String photoFile = "Latest.jpg";

        String filename = pictureFileDir.getPath() + File.separator + photoFile;

        File pictureFile = new File(filename);

        try {
            FileOutputStream fos = new FileOutputStream(pictureFile);
            fos.write(data);
            fos.close();
            Toast.makeText(CameraCaptureActivity.this, "Image saved:" + photoFile,
                    Toast.LENGTH_LONG).show();

            // Restart the preview and re-enable the shutter button so that we can take another picture
            camera.stopPreview();
            shutterButton.setEnabled(false);         

        } catch (Exception error) {            
            Toast.makeText(CameraCaptureActivity.this, "Image could not be saved.",
                    Toast.LENGTH_LONG).show();
        }
    }

    private File getDir() {
        File sdDir = Environment
          .getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
        return new File(sdDir, "Latest Models");
    }


    public void onResume() 
    {
        super.onResume();
        shutterButton.setEnabled(true);
    }

}

CameraSurfaceView.java:-

class CameraSurfaceView extends SurfaceView implements SurfaceHolder.Callback {

    Camera camera;

    CameraSurfaceView(Context context) {
        super(context);

        SurfaceHolder holder = this.getHolder();
        holder.addCallback(this);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
                               int height) {

        camera.setDisplayOrientation(90);    
        camera.startPreview();
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        try {
            // Open the Camera in preview mode
            this.camera = Camera.open();
            this.camera.setPreviewDisplay(holder);
        } catch (IOException ioe) {
            ioe.printStackTrace(System.out);
        }

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {            
        camera.stopPreview();
        camera.release();
        camera = null;
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        // TODO Auto-generated method stub
    }

    public void takePicture(PictureCallback imageCallback) {
        camera.takePicture(null, null, imageCallback);
    }

}

Answer 1

试试下面的代码，可能对你有帮助

首先将图像转换为所需的高度和宽度

public static Bitmap scaleImage(String p_path, int p_reqHeight, int p_reqWidth) throws Throwable
{
    Bitmap m_bitMap = null;
    System.gc();
    File m_file = new File(p_path);
    if (m_file.exists())
    {
        BitmapFactory.Options m_bitMapFactoryOptions = new BitmapFactory.Options();
        m_bitMapFactoryOptions.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(m_file.getPath(), m_bitMapFactoryOptions);
        m_bitMapFactoryOptions.inSampleSize = calculateInSampleSize(m_bitMapFactoryOptions, p_reqHeight, p_reqWidth);
        m_bitMapFactoryOptions.inJustDecodeBounds = false;
        m_bitMap = BitmapFactory.decodeFile(m_file.getPath(), m_bitMapFactoryOptions);
    }
    else
    {
        throw new Throwable(p_path + " not found or not a valid image");
    }
    return m_bitMap;
}


private static int calculateInSampleSize(BitmapFactory.Options p_options, int p_reqWidth, int p_reqHeight)
{
    // Raw height and width of image
    final int m_height = p_options.outHeight;
    final int m_width = p_options.outWidth;
    int m_inSampleSize = 1;
    if (m_height > p_reqHeight || m_width > p_reqWidth)
    {
        final int m_halfHeight = m_height / 2;
        final int m_halfWidth = m_width / 2;
        // Calculate the largest inSampleSize value that is a power of 2 and keeps both
        // height and width larger than the requested height and width.
        while ((m_halfHeight / m_inSampleSize) > p_reqHeight && (m_halfWidth / m_inSampleSize) > p_reqWidth)
        {
            m_inSampleSize *= 2;
        }
    }
    return m_inSampleSize;
}

Answer 2

写入数据后使用 FileOutputStream.flush()...

File file = new File(fileName.toString());
try {
    FileOutputStream stream = new FileOutputStream(file);
    bitmap.compress(CompressFormat.PNG, 100, stream);
    stream.flush();
    stream.close();
} catch (Exception e) {
    // TODO: handle exception
}

您可以按照以下代码保存位图图像

Bitmap photo = (Bitmap) "your Bitmap image";
photo = Bitmap.createScaledBitmap(photo, 100, 100, false);
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
photo.compress(Bitmap.CompressFormat.JPEG, 40, bytes);

File f = new File(Environment.getExternalStorageDirectory()
        + File.separator + "Imagename.jpg");
f.createNewFile();
FileOutputStream fo = new FileOutputStream(f);
fo.write(bytes.toByteArray());
fo.close();