为什么android在显示png文件时会丢失图像质量？

Question

I want to display a png image on android. This is the image file:

The right end is a bit darker than left.

But the quality of image lost on android application(using ImageView):

Please note part in the red frame. The color is not changing smoothly.

But if I use the browser of my android phone, it plays good(so it's not reason of the phone screen):

This is my android code, which is pretty simple:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent">
    <ImageView android:layout_width="wrap_content"
               android:layout_height="wrap_content"
               android:background="@drawable/hhh"/>
</LinearLayout>

where hhh is my first image posted here, which is under res/drawable .

I test it on my android phone(android 2.3.6) and android simulator(with android 2.2/2.3/4.0), all do not display good. But it plays good on my android pad(android 4.0.3).

What's the problem, and how to fix it?

Answer 1

Images in res/drawable are compressed. This is supposed to be lossless , but I've heard of similar issues in the past.

Move it into res/raw , and give it a go.

Answer 2

Try adding the following to your Activity and see if it helps.

@Override
public void onAttachedToWindow() {
   super.onAttachedToWindow();
   Window window = getWindow();
   //eliminates color banding
   window.setFormat(PixelFormat.RGBA_8888);
}

Answer 3

这个问题是众所周知的，它是一个渐变条带问题，我有这个问题并通过添加噪声来解决，例如http://planetphotoshop.com/say-goodbye-to-gradient-banding.html