android - 如何在 Android 中从 ImageView 中的相机显示中获取图像而不损失其质量？

Question

我使用这个简单的代码从相机捕获图像。我发现这个问题很多并且尝试了很多方法但无法解决这个问题。当我捕获图像时，我的图像大部分是 PDF，由于像素较差，它变得不可读

 private static final int CAMERA_REQUEST = 1888;
            private ImageView imageView;
            private static final int MY_CAMERA_PERMISSION_CODE = 100;
            ImageView Image;


            private static final int REQUEST_CAPTURE_IMAGE = 100;

            @Override
            protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.activity_camera_test);
                Image = (ImageView) findViewById(R.id.Image);
                Button camera = (Button) findViewById(R.id.camera);
                camera.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {

                        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                            if (checkSelfPermission(Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED)
                            {
                                requestPermissions(new String[]{Manifest.permission.CAMERA}, MY_CAMERA_PERMISSION_CODE);
                            }
                            else
                            {
                                Intent cameraIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                                startActivityForResult(cameraIntent, CAMERA_REQUEST);
                            }
                        }
                    }

                });



            }




 @Override
        public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults)
        {
            super.onRequestPermissionsResult(requestCode, permissions, grantResults);
            if (requestCode == MY_CAMERA_PERMISSION_CODE)
            {
                if (grantResults[0] == PackageManager.PERMISSION_GRANTED)
                {
                    Toast.makeText(this, "camera permission granted", Toast.LENGTH_LONG).show();
                    Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
                    startActivityForResult(cameraIntent, CAMERA_REQUEST);
                }
                else
                {
                    Toast.makeText(this, "camera permission denied", Toast.LENGTH_LONG).show();
                }
            }
        }




  @Override
        protected void onActivityResult(int requestCode, int resultCode, Intent data)
        {
            if (requestCode == CAMERA_REQUEST && resultCode == Activity.RESULT_OK)
            {
                Bitmap photo = (Bitmap) data.getExtras().get("data");
                Image.setImageBitmap(photo);
            }
        }

我使用这个简单的代码从相机捕获图像。我发现这个问题很多并且尝试了很多方法但无法解决这个问题。当我捕获图像时，我的图像大部分是 PDF，由于像素较差，它变得不可读

Answer 1

如果您需要最佳质量的图像，则需要将其保存到文件中，否则您只能访问缩略图(低分辨率图像)。我将分享我是如何做到的。

在 list 中，您需要在应用程序标记内定义文件提供程序以及权限。

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.CAMERA" />
<application...>
...
    <provider
        android:name="androidx.core.content.FileProvider"
        android:authorities="{your package name}.fileprovider"
        android:exported="false"
        android:grantUriPermissions="true">
        <meta-data
            android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/file_path" />
    </provider>
</application>

您还需要在 res/xml 文件夹中创建一个 FileProvider。我的看起来像这样:

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="/storage/emulated/0/Pictures/" path="Pictures/"/>
</paths>

请多做研究，您想将照片保存在哪里，在我的示例中，您只能将它们保存到 SD 卡，但还有更多选项。

现在，拍照并保存。

private var currentPhotoUri = Uri.EMPTY
private var currentPhotoPath
private val requestCode = 123

private fun dispatchTakePictureIntent() {
    Intent(MediaStore.ACTION_IMAGE_CAPTURE).also { takePictureIntent ->
        // Ensure that there's a camera activity to handle the intent
        takePictureIntent.resolveActivity(activity?.packageManager!!)?.also {

            createFile()

            takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, currentFileUri)
            startActivityForResult(takePictureIntent, requestCode)
        }
    }
}

private fun createFile(): File? {
    val photoFile: File? = try {
        createImageFile()
    } catch (ex: IOException) {
        Log.i("mylog error", "Error creating file: " + ex.toString())
        ex.printStackTrace()
        null
    }
    // Continue only if the File was successfully created
    photoFile?.also {
        val photoURI: Uri = context?.let { context ->
            FileProvider.getUriForFile(
                    context,
                    "{your package name}.fileprovider",
                    it
            )
        } as Uri
        currentPhotoUri = photoURI

    }
    return photoFile
}

private fun createImageFile(): File {
    val timeStamp: String = SimpleDateFormat("yyyyMMdd_HHmmss").format(Date())
    val storageDir: File? = context!!.getExternalFilesDir(Environment.DIRECTORY_PICTURES)
    Log.i("mylog", "storage dir = " + storageDir?.absolutePath)
    return File.createTempFile(
            "JPEG_${timeStamp}_", /* prefix */
            ".jpg", /* suffix */
            storageDir /* directory */
    ).apply {
        // Save a file: path for use with ACTION_VIEW intents
        currentPhotoPath = absolutePath
    }

}

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent) 
{
    if (requestCode == requestCode && resultCode == RESULT_OK) {
        val bitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(),currentPhotoUri)
        val imageView = findViewById(R.id.Image)
        imageView.setImageBitmap(bitmap)
    }
}

这应该有效。不要忘记检查权限。您可以了解更多here .