图片之间的转换

1.url转bitmap

public void returnBitMap(final String url, final CommonCallback<Bitmap> callback) {
    new Thread(new Runnable() {
        @Override
        public void run() {
            URL imageurl = null;

            try {
                imageurl = new URL(url);
            } catch (MalformedURLException e) {
                e.printStackTrace();
                if (callback!=null){
                    callback.callback(null);
                }
            }
            try {
                HttpURLConnection conn = (HttpURLConnection) imageurl.openConnection();
                conn.setDoInput(true);
                conn.connect();
                InputStream is = conn.getInputStream();
                Bitmap bitmap = BitmapFactory.decodeStream(is);
                is.close();


                //----圆形bitmap----
                int width = bitmap.getWidth();
                int height = bitmap.getHeight();
                int left = 0, top = 0, right = width, bottom = height;
                float roundPx = height/2;
                if (width > height) {
                    left = (width - height)/2;
                    top = 0;
                    right = left + height;
                    bottom = height;
                } else if (height > width) {
                    left = 0;
                    top = (height - width)/2;
                    right = width;
                    bottom = top + width;
                    roundPx = width/2;
                }

                Bitmap output = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
                Canvas canvas = new Canvas(output);
                int color = 0xff424242;
                Paint paint = new Paint();
                Rect rect = new Rect(left, top, right, bottom);
                RectF rectF = new RectF(rect);

                paint.setAntiAlias(true);
                canvas.drawARGB(0, 0, 0, 0);
                paint.setColor(color);
                canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
                paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
                canvas.drawBitmap(bitmap, rect, rect, paint);
                //----圆形bitmap----


                if (callback!=null){
                    callback.callback(output);
                }
            } catch (IOException e) {
                e.printStackTrace();
                if (callback!=null){
                    callback.callback(null);
                }
            }
        }
    }).start();

}

2.id转drawable

   Drawable drawable = getResources().getDrawable(R.mipmap.xxx);

3.id转bitmap

Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.xxx);

3.drawable转bitmap

 (1). BitmapDrawable, FastBitmapDrawable 调用getBitmap
 (2). Canvas绘图bitmap：
      Canvas canvas = new Canvas(bitmap)
      drawable.draw(canvas)

4. bitmap转drawable

Drawable drawable = new FastBitmapDrawable(bitmap);

5.url转drawable

InputStream is2 = null;
try {
    is2 = (InputStream) new URL(url).getContent();
} catch (IOException e) {
    e.printStackTrace();
}
Drawable d = Drawable.createFromStream(is2, "src");
try {
    is2.close();
} catch (IOException e) {
    e.printStackTrace();
}