如何从Android中的BitmapDrawable或位图图像中删除白色背景色？

Question

I want to remove the white background color in a bitmap like in this example image.

This is my first try :

BitmapDrawable drawableImg = getImage();
drawableImg.setColorFilter(new PorterDuffColorFilter(Color.WHITE,
PorterDuff.Mode.DST_OUT));

Second try :

To remove the white colors range by setting fromBgColor and toBgColor, But when I replace the color with android transparent color the image turns into black here is the code:

public static Bitmap getBitmapWithTransparentBG(Bitmap srcBitmap, 
       int fromBgColor, int toBgColor) {
    Bitmap result = srcBitmap.copy(Bitmap.Config.ARGB_8888, true);
    int nWidth = result.getWidth();
    int nHeight = result.getHeight();
    for (int y = 0; y < nHeight; ++y)
        for (int x = 0; x < nWidth; ++x) {
            int nPixelColor = result.getPixel(x, y);
            if (nPixelColor >= fromBgColor && nPixelColor <= toBgColor)
                result.setPixel(x, y, Color.TRANSPARENT);
        }
    return result;
}

Hint I had a hint that bitmap does not support transparent bits and I should use PNG or Gif instead of bitmaps is that right?

Hint 2 It turned out that bitmap in Android has an option to show transparency since API level 1 using Bitmap.Config enum. Check this link in the documentation of Android.

Answer 1

what is beneath your image? Maybe it could be a layout issue. Have you tried setting android:background="@android:color/transparent" in the xml? I see you tried the getBitmapWithTransparentBG described in Android: Make specific (green) color in background image transparent But have you tried also this? How to change colors of a Drawable in Android? About the image being jpg or png, I've managed to work with both after loading and setting it to a imageview (getting the bitmap back from it), and it allows to set the transparency using the getBitmapWithTransparentBG function as quoted above.