使用 WRITE_EXTERNAL_STORAGE 在 Android 中将位图存储为 jpg

Question

我期待 Android 应用程序画图，它可以显示图像的预览。我想将绘制的图像以 JPEG 或 PNG 格式存储到我设备的外部或内部存储器中。请在这件事上给予我帮助以下是 MainActitvity.java 文件的代码：

package ai.fritz.tflitedemo;

import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import java.io.*;
import java.util.*;
import java.util.Map;
import android.os.Environment;
import java.io.File;
import android.Manifest;
import android.app.Activity;
import android.support.v4.app.ActivityCompat;

import ai.fritz.tflitedemo.ml.DigitsDetector;
import ai.fritz.tflitedemo.ui.PaintView;
import butterknife.BindView;
import butterknife.ButterKnife;



public class MainActivity extends AppCompatActivity {
private final String TAG = this.getClass().getSimpleName();
private static final int PIXEL_WIDTH = 28;
private DigitsDetector mnistClassifier;

@BindView(R.id.button_detect)
View detectButton;

@BindView(R.id.button_clear)
View clearButton;

@BindView(R.id.text_result)
TextView mResultText;

@BindView(R.id.paintView)
PaintView paintView;

@BindView(R.id.preview_image)
ImageView previewImage;

@BindView(R.id.inference_preview)
LinearLayout inferencePreview;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    setTitle(R.string.app_name);
    ButterKnife.bind(this);

    ActivityCompat.requestPermissions(MainActivity.this,new String[] 
  {Manifest.permission.WRITE_EXTERNAL_STORAGE},1);
    mnistClassifier = new DigitsDetector(this);

    DisplayMetrics metrics = new DisplayMetrics();
    getWindowManager().getDefaultDisplay().getMetrics(metrics);
    paintView.init(metrics);

    detectButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            onDetectClicked();
        }
    });

    clearButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            onClearClicked();
        }
    });
}


private void onDetectClicked() {
    inferencePreview.setVisibility(View.VISIBLE);
    Bitmap scaledBitmap = Bitmap.createScaledBitmap(paintView.getBitmap(), PIXEL_WIDTH, PIXEL_WIDTH, false);
    int digit = mnistClassifier.classify(scaledBitmap);
    previewImage.setImageBitmap(scaledBitmap);

    SaveImage(scaledBitmap);
    if (digit >= 0) {
        Log.d(TAG, "Found Digit = " + digit);
        mResultText.setText(getString(R.string.found_digits, String.valueOf(digit)));
    } else {
        mResultText.setText(getString(R.string.not_detected));
    }
}
private void SaveImage(Bitmap finalBitmap) {

    File root = Environment.getExternalStorageDirectory();
    //Path path = FileSystems.getDefault().getPath("logs", "access.log");
    File myDir = new File(root+"/saved_images");
    Log.d("root",myDir.toString());
    if (!myDir.exists()) {
        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);
        finalBitmap.compress(Bitmap.CompressFormat.PNG, 90, out);
        out.flush();
        out.close();

    } catch (Exception e) {
        e.printStackTrace();
    }
}
private void onClearClicked() {
    mResultText.setText("");
    paintView.clear();
}
 }

权限访问代码如下：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

它抛出错误，指出找不到文件的来源

java.io.FileNotFoundException: /storage/emulated/0/saved_images/Image- 
6131.jpg: open failed: ENOENT (No such file or directory)

。但是预览效果很好。

我想将绘制的图像存储为jpg文件。

提前致谢

Answer 1

对于 Android 8+ 你需要 READ_EXTERNAL_STORAGE 和 WRITE_EXTERNAL_STORAGE

询问权限：

private static final int REQUEST_STORAGE = 1111;

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
  if ((checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) || (checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED)) {
requestPermissions(new String[]{android.Manifest.permission.READ_EXTERNAL_STORAGE, android.Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_STORAGE);
  }
}

这里你会得到结果：

@TargetApi(23)
    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode) {
            case REQUEST_STORAGE: {
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    //Toast.makeText(getBaseContext(), getResources().getString(R.string.permission_ok), Toast.LENGTH_SHORT).show();
                    recreate();                 
                } else {
                    AlertDialog.Builder builder = new AlertDialog.Builder(new ContextThemeWrapper(this, R.style.AlertDialogCustom));
                    builder.setTitle(getResources().getString(R.string.assign_permissions));
                    builder.setMessage(getResources().getString(R.string.permissions_denied));
                    builder.setPositiveButton(getResources().getString(android.R.string.ok), new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {

                            finish();
                            dialog.dismiss();

                        }
                    });
                    builder.show();
                }
                break;
            }
        }

    }

使用 WRITE_EXTERNAL_STORAGE 在 Android 中将位图存储为 jpg

Storing Bitmap to jpg in Android using WRITE_EXTERNAL_STORAGE

android

android-storage