// 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);
        }
    }
}

BitmapFactory.decodeResource()自动缩放位图，因此您的位图可能会变得模糊。为了防止结垢，请这样做:

BitmapFactory.Options options = new BitmapFactory.Options();
options.inScaled = false;
Bitmap source = BitmapFactory.decodeResource(context.getResources(),
                                             R.drawable.resource_name, options);

or

InputStream is = context.getResources().openRawResource(R.drawable.resource_name)
bitmap = BitmapFactory.decodeStream(is);

所以在看了(和使用)其他答案后，似乎他们都处理ColorDrawable和PaintDrawable很糟糕。(特别是在棒棒糖上)似乎着色器被调整了，所以固体块的颜色没有被正确处理。

我现在使用以下代码:

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

    // We ask for the bounds if they have been set as they would be most
    // correct, then we check we are  > 0
    final int width = !drawable.getBounds().isEmpty() ?
            drawable.getBounds().width() : drawable.getIntrinsicWidth();

    final int height = !drawable.getBounds().isEmpty() ?
            drawable.getBounds().height() : drawable.getIntrinsicHeight();

    // Now we check we are > 0
    final Bitmap bitmap = Bitmap.createBitmap(width <= 0 ? 1 : width, height <= 0 ? 1 : height,
            Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bitmap);
    drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
    drawable.draw(canvas);

    return bitmap;
}

与其他方法不同，如果你在要求将Drawable转换为位图之前调用setBounds，它将以正确的大小绘制位图!

最新的androidx核心库(androidx.core:core-ktx:1.2.0)现在有一个扩展函数:Drawable. tobitmap(…)来将Drawable转换为Bitmap。

1)可绘制位图:

Bitmap mIcon = BitmapFactory.decodeResource(context.getResources(),R.drawable.icon);
// mImageView.setImageBitmap(mIcon);

2)位图到可绘制:

Drawable mDrawable = new BitmapDrawable(getResources(), bitmap);
// mImageView.setDrawable(mDrawable);

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