等比缩放Bitmap至新宽高并裁剪掉额外部分

private static Bitmap createScaledBitmap(Bitmap bm, int newWidth, int newHeight) {
        int w = bm.getWidth(); // 得到图片的宽，高
        int h = bm.getHeight();
        int retX;
        int retY;
        double wh = (double) w / (double) h;
        double nwh = (double) newWidth / (double) newHeight;
        if (wh > nwh) {
            retX = h * newWidth / newHeight;
            retY = h;
        } else {
            retX = w;
            retY = w * newHeight / newWidth;
        }
        int startX = w > retX ? (w - retX) / 2 : 0;//基于原图，取正方形左上角x坐标
        int startY = h > retY ? (h - retY) / 2 : 0;
        Bitmap bit = Bitmap.createBitmap(bm, startX, startY, retX, retY, null, false);
        bm.recycle();
        return bit;
}

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