geopackage-sdk/src/main/java/mil/nga/geopackage/tiles/features/FeatureTiles.java
protected Bitmap checkIfDrawn(Bitmap bitmap) {
        if (isTransparent(bitmap)) {
            bitmap.recycle();
            bitmap = null;
        }
        return bitmap;
    }
protected Bitmap checkIfDrawn(Bitmap bitmap) {
        if (isTransparent(bitmap)) {
            bitmap.recycle();
            bitmap = null;
        }
        return bitmap;
    }
Check if the bitmap was drawn upon (non null and not transparent). Return the same bitmap if drawn, else recycle non null bitmaps and return null

@param bitmap bitmap
@return drawn bitmap or null