Home/ Questions/Q 6942295
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-27T12:59:49+00:00

I’m working on a Gingerbread (2.3.3) device. I have an ImageView which contains an

  • 0

I’m working on a Gingerbread (2.3.3) device. I have an ImageView which contains an arrow figure and have a fully transparent background which I need to draw on some background. The problem is that there’s a “shading” artifact beneath the ImageView’s bounding box.
If you look closely on the following image, you’ll see the artifact i’m talking about: 1

Both the foreground image and the background image have alpha channels and therefore are decoded as ARGB8888 (I double checked this by manually decoding their resources into a bitmap, print out the bitmap configuration which showed ARGB8888, and then assigning them to their respective views). I also configured the Activitiy’s window to be PixelFormat.RGBA_8888 before the call to setContentView().

Please don’t refer me to threads that suggest decoding the bitmap as ARGB8888 and/or set the window to be RGBA_8888, since I tried both solutions, which didn’t help.

Any ideas how can I fix this issue?

EDIT:

Here’s the function which sets the Window pixel format and drawables (called directly from onCreate()):

public void testTransparency() {
    getWindow().setFormat(PixelFormat.RGBA_8888);
    setContentView(R.layout.transparency_test);
    LinearLayout ll = (LinearLayout)findViewById(R.id.ll);      
    Bitmap bgBmp = BitmapFactory.decodeResource(getResources(), R.raw.bg);
    Log.d(TAG,"BG BMP Config: " + bgBmp.getConfig());
    ll.setBackgroundDrawable(new BitmapDrawable(bgBmp));
    ImageView iv = (ImageView)findViewById(R.id.iv);
    iv.setBackgroundDrawable(null);
    Bitmap arrowBmp = BitmapFactory.decodeResource(getResources(), R.raw.big_arrow);
    Log.d(TAG,"Arrow BMP Config: " + arrowBmp.getConfig());
    iv.setImageBitmap(arrowBmp);
}

And here’s the (very simple) layout my test is using:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    android:id="@+id/ll"  
    android:layout_width="fill_parent"  
    android:layout_height="fill_parent"  
    android:orientation="vertical"  
    android:gravity="center">

<ImageView android:id="@+id/iv"
    android:layout_width="72dp"
    android:layout_height="120dp"
    /></LinearLayout>

The ‘bg’ resource can be found at 2
The ‘big_arrow’ resource can be found at “http://i.imgur.com/3V6QU.png&#8221;

EDIT 2:
I found out I can’t reproduce the problem on the emulator, nor on my N1 (2.3.4) or XOOM (3.2.1). There are 2 options continuing from here:
1. The problem is device specific (Android based appliance i’m working on)
2. There’s a specific problem with 2.3.4 and 32BPP framebuffer while rendering transparent PNGs on top of each other.

Thanks.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Found the bug and indeed it was a platform specific bug.

    I found out when I remove the neon optimizations in the blended blitting portion of SKIA (in SkBlitRow_D32.cpp – SkBlitRow::Proc32 SkBlitRow::Factory32(unsigned flags)), the shading artifact disappears.

    A useful tip for anyone who want to debug this sort of bugs:
    You can always draw your view hierarchy to a bitmap (See: Android get a bitmap of a view before drawing? for example) and then use Bitmap.compress method to export the bitmap to a PNG file. This way you can obtain your view hierarchy snapshot with its alpha channel (Which doesn’t appear in A DDMS screenshot since it’s generated after composition). I found out this way that the alpha value within the shaded area is ‘1’ instead of ‘0’, creating the artifact.

    • 0