Rotated ImageView edges are not smooth (jagged)

Question

Sample NG ImageView: NG Rotated ImageView

In iOS, i can easily solve this jagged-edges-problem by view.layer.allowsEdgeAntialiasing = true. What is the best way to solve this in Android?

What I already tried:
I referred to this post Bitmap not drawn anti-aliased and set android:layerType="software" but result is still NG.

<ImageView
        android:id="@+id/imageView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layerType="software"
        android:rotation="5"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/pic" />

Expected result: smooth (anti-aliased) edges
Actual result: not smooth (jagged) edges

ghostcat47 · Accepted Answer · 2019-05-31T07:25:40.307

So after experimenting for a while, this is the best that I could achieve:

1) Test output: NG vs OK

2) NG output source

*xml only (under ConstraintLayout)

<ImageView android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           app:layout_constraintTop_toTopOf="parent"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintBottom_toBottomOf="parent"
           android:id="@+id/test3"
           app:srcCompat="@drawable/sampleImg"
           android:rotation="5"/>

3) OK output source

*xml (under ConstraintLayout)

<test.ntfry.imageview_rotate_antialias.MyImageView
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           app:layout_constraintTop_toTopOf="parent"                                   
           app:layout_constraintStart_toStartOf="parent"                                    
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintBottom_toBottomOf="parent"
           android:id="@+id/test2"/>

*Custom ImageView class

class MyImageView : AppCompatImageView {

    private val mPaint = Paint(Paint.ANTI_ALIAS_FLAG)
    private val mMatrix = Matrix()
    private var mRotatedBitmap: Bitmap? = null
    private val mRotation = 5F

    constructor(context: Context) : super(context, null) {
        init()
    }
    constructor(context: Context, attrs: AttributeSet?) : super(context, attrs) {
        init()
    }
    constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super(context, attrs, defStyleAttr) {
        init()
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        setMeasuredDimension(mRotatedBitmap!!.width, mRotatedBitmap!!.height)
    }

    override fun onDraw(canvas: Canvas?) {
        super.onDraw(canvas)
        canvas?.drawBitmap(mRotatedBitmap!!, 0f, 0f, mPaint)
    }

    private fun init() {
        // https://stackoverflow.com/questions/14378573/bitmap-not-drawn-anti-aliased
        setLayerType(LAYER_TYPE_SOFTWARE, null)

        // get source image and set-apply rotation through matrix
        val sourceBitmap = BitmapFactory.decodeResource(resources, R.drawable.sampleImg)
        mMatrix.postRotate(mRotation)
        mRotatedBitmap = Bitmap.createBitmap(sourceBitmap, 0, 0, sourceBitmap.width, sourceBitmap.height, mMatrix, true)
    }
}

4) If you have a better solution, by all means please comment/share your idea! Thanks^^

Rotated ImageView edges are not smooth (jagged)

1 Answers1