一个可绘制对象可以被绘制到画布上，一个画布可以被位图支持:

(更新到处理BitmapDrawables的快速转换，并确保创建的位图具有有效的大小)

public static Bitmap drawableToBitmap (Drawable drawable) {
    if (drawable instanceof BitmapDrawable) {
        return ((BitmapDrawable)drawable).getBitmap();
    }

    int width = drawable.getIntrinsicWidth();
    width = width > 0 ? width : 1;
    int height = drawable.getIntrinsicHeight();
    height = height > 0 ? height : 1;

    Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bitmap); 
    drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
    drawable.draw(canvas);

    return bitmap;
}

方法1:你可以像这样直接转换成位图

Bitmap myLogo = BitmapFactory.decodeResource(context.getResources(), R.drawable.my_drawable);

方法2:你甚至可以把资源转换成可绘制的，从那里你可以得到像这样的位图

Bitmap myLogo = ((BitmapDrawable)getResources().getDrawable(R.drawable.logo)).getBitmap();

对于API > 22 getDrawable方法移动到ResourcesCompat类，因此你可以这样做

Bitmap myLogo = ((BitmapDrawable) ResourcesCompat.getDrawable(context.getResources(), R.drawable.logo, null)).getBitmap();

 // get image path from gallery
protected void onActivityResult(int requestCode, int resultcode, Intent intent) {
    super.onActivityResult(requestCode, resultcode, intent);

    if (requestCode == 1) {
        if (intent != null && resultcode == RESULT_OK) {             
            Uri selectedImage = intent.getData();

            String[] filePathColumn = {MediaStore.Images.Media.DATA};
            Cursor cursor = getContentResolver().query(selectedImage, filePathColumn, null, null, null);
            cursor.moveToFirst();
            int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
            filePath = cursor.getString(columnIndex);

            //display image using BitmapFactory

            cursor.close(); bmp = BitmapFactory.decodeFile(filepath); 
            iv.setBackgroundResource(0);
            iv.setImageBitmap(bmp);
        }
    }
}

public static Bitmap drawableToBitmap (Drawable drawable) {
    Bitmap bitmap = null;

    if (drawable instanceof BitmapDrawable) {
        BitmapDrawable bitmapDrawable = (BitmapDrawable) drawable;
        if(bitmapDrawable.getBitmap() != null) {
            return bitmapDrawable.getBitmap();
        }
    }

    if(drawable.getIntrinsicWidth() <= 0 || drawable.getIntrinsicHeight() <= 0) {
        bitmap = Bitmap.createBitmap(1, 1, Bitmap.Config.ARGB_8888); // Single color bitmap will be created of 1x1 pixel
    } else {
        bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
    }

    Canvas canvas = new Canvas(bitmap);
    drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
    drawable.draw(canvas);
    return bitmap;
}

Bitmap Bitmap = BitmapFactory.decodeResource(context.getResources()， R.drawable.icon);

这将不会每次工作，例如，如果你的可绘制层列表可绘制，然后它给出一个空响应，所以作为一个替代方案，你需要绘制你的可绘制到画布，然后保存为位图，请参考下面的一杯代码。

public void drawableToBitMap(Context context, int drawable, int widthPixels, int heightPixels) {
    try {
        File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) + "/", "drawable.png");
        FileOutputStream fOut = new FileOutputStream(file);
        Drawable drw = ResourcesCompat.getDrawable(context.getResources(), drawable, null);
        if (drw != null) {
            convertToBitmap(drw, widthPixels, heightPixels).compress(Bitmap.CompressFormat.PNG, 100, fOut);
        }
        fOut.flush();
        fOut.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

private Bitmap convertToBitmap(Drawable drawable, int widthPixels, int heightPixels) {
    Bitmap bitmap = Bitmap.createBitmap(widthPixels, heightPixels, Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bitmap);
    drawable.setBounds(0, 0, widthPixels, heightPixels);
    drawable.draw(canvas);
    return bitmap;
}

以上代码保存为drawable.png在下载目录

ImageWorker库可以将位图转换为可绘制或base64，反之亦然。

val bitmap: Bitmap? = ImageWorker.convert().drawableToBitmap(sourceDrawable)

实现

在项目级别Gradle

allprojects {
        repositories {
            ...
            maven { url 'https://jitpack.io' }
        }
    }

在应用级Gradle

dependencies {
            implementation 'com.github.1AboveAll:ImageWorker:0.51'
    }

您还可以从外部存储和检索位图/绘图/base64图像。

检查在这里。https://github.com/1AboveAll/ImageWorker/edit/master/README.md