我们在做项目的时候有时候需要给图片添加水印，水寒今天就遇到了这样的问题，所以搞了一个工具类，贴出来大家直接调用就行。

/** * 图片工具类 * @author 水寒 * 欢迎访问水寒的个人博客：http://www.sunhome.org.cn * */public class ImageUtil {
         /**     * 设置水印图片在左上角     * @param Context     * @param src     * @param watermark     * @param paddingLeft     * @param paddingTop     * @return     */    public static Bitmap createWaterMaskLeftTop(            Context context, Bitmap src, Bitmap watermark,            int paddingLeft, int paddingTop) {        return createWaterMaskBitmap(src, watermark,                 dp2px(context, paddingLeft), dp2px(context, paddingTop));    }    private static Bitmap createWaterMaskBitmap(Bitmap src, Bitmap watermark,            int paddingLeft, int paddingTop) {        if (src == null) {            return null;        }        int width = src.getWidth();        int height = src.getHeight();        //创建一个bitmap        Bitmap newb = Bitmap.createBitmap(width, height, Config.ARGB_8888);// 创建一个新的和SRC长度宽度一样的位图        //将该图片作为画布        Canvas canvas = new Canvas(newb);        //在画布 0，0坐标上开始绘制原始图片        canvas.drawBitmap(src, 0, 0, null);        //在画布上绘制水印图片        canvas.drawBitmap(watermark, paddingLeft, paddingTop, null);        // 保存        canvas.save(Canvas.ALL_SAVE_FLAG);        // 存储        canvas.restore();        return newb;    }    /**     * 设置水印图片在右下角     * @param Context     * @param src     * @param watermark     * @param paddingRight     * @param paddingBottom     * @return     */    public static Bitmap createWaterMaskRightBottom(            Context context, Bitmap src, Bitmap watermark,            int paddingRight, int paddingBottom) {        return createWaterMaskBitmap(src, watermark,                 src.getWidth() - watermark.getWidth() - dp2px(context, paddingRight),                 src.getHeight() - watermark.getHeight() - dp2px(context, paddingBottom));    }    /**     * 设置水印图片到右上角     * @param Context     * @param src     * @param watermark     * @param paddingRight     * @param paddingTop     * @return     */    public static Bitmap createWaterMaskRightTop(            Context context, Bitmap src, Bitmap watermark,            int paddingRight, int paddingTop) {        return createWaterMaskBitmap( src, watermark,                 src.getWidth() - watermark.getWidth() - dp2px(context, paddingRight),                 dp2px(context, paddingTop));    }    /**     * 设置水印图片到左下角     * @param Context     * @param src     * @param watermark     * @param paddingLeft     * @param paddingBottom     * @return     */    public static Bitmap createWaterMaskLeftBottom(            Context context, Bitmap src, Bitmap watermark,            int paddingLeft, int paddingBottom) {        return createWaterMaskBitmap(src, watermark, dp2px(context, paddingLeft),                 src.getHeight() - watermark.getHeight() - dp2px(context, paddingBottom));    }    /**     * 设置水印图片到中间     * @param Context     * @param src     * @param watermark     * @return     */    public static Bitmap createWaterMaskCenter(Bitmap src, Bitmap watermark) {        return createWaterMaskBitmap(src, watermark,                 (src.getWidth() - watermark.getWidth()) / 2,                (src.getHeight() - watermark.getHeight()) / 2);    }    /**     * 给图片添加文字到左上角     * @param context     * @param bitmap     * @param text     * @return     */    public static Bitmap drawTextToLeftTop(Context context, Bitmap bitmap, String text,            int size, int color, int paddingLeft, int paddingTop) {        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);        paint.setColor(color);        paint.setTextSize(dp2px(context, size));        Rect bounds = new Rect();        paint.getTextBounds(text, 0, text.length(), bounds);        return drawTextToBitmap(context, bitmap, text, paint, bounds,                 dp2px(context, paddingLeft),                  dp2px(context, paddingTop) + bounds.height());    }    /**     * 绘制文字到右下角     * @param context     * @param bitmap     * @param text     * @param size     * @param color     * @param paddingLeft     * @param paddingTop     * @return     */    public static Bitmap drawTextToRightBottom(Context context, Bitmap bitmap, String text,            int size, int color, int paddingRight, int paddingBottom) {        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);        paint.setColor(color);        paint.setTextSize(dp2px(context, size));        Rect bounds = new Rect();        paint.getTextBounds(text, 0, text.length(), bounds);        return drawTextToBitmap(context, bitmap, text, paint, bounds,                 bitmap.getWidth() - bounds.width() - dp2px(context, paddingRight),                 bitmap.getHeight() - dp2px(context, paddingBottom));    }    /**     * 绘制文字到右上方     * @param context     * @param bitmap     * @param text     * @param size     * @param color     * @param paddingRight     * @param paddingTop     * @return     */    public static Bitmap drawTextToRightTop(Context context, Bitmap bitmap, String text,            int size, int color, int paddingRight, int paddingTop) {        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);        paint.setColor(color);        paint.setTextSize(dp2px(context, size));        Rect bounds = new Rect();        paint.getTextBounds(text, 0, text.length(), bounds);        return drawTextToBitmap(context, bitmap, text, paint, bounds,                 bitmap.getWidth() - bounds.width() - dp2px(context, paddingRight),                 dp2px(context, paddingTop) + bounds.height());    }    /**     * 绘制文字到左下方     * @param context     * @param bitmap     * @param text     * @param size     * @param color     * @param paddingLeft     * @param paddingBottom     * @return     */    public static Bitmap drawTextToLeftBottom(Context context, Bitmap bitmap, String text,            int size, int color, int paddingLeft, int paddingBottom) {        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);        paint.setColor(color);        paint.setTextSize(dp2px(context, size));        Rect bounds = new Rect();        paint.getTextBounds(text, 0, text.length(), bounds);        return drawTextToBitmap(context, bitmap, text, paint, bounds,                 dp2px(context, paddingLeft),                  bitmap.getHeight() - dp2px(context, paddingBottom));    }    /**     * 绘制文字到中间     * @param context     * @param bitmap     * @param text     * @param size     * @param color     * @return     */    public static Bitmap drawTextToCenter(Context context, Bitmap bitmap, String text,            int size, int color) {        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);        paint.setColor(color);        paint.setTextSize(dp2px(context, size));        Rect bounds = new Rect();        paint.getTextBounds(text, 0, text.length(), bounds);        return drawTextToBitmap(context, bitmap, text, paint, bounds,                 (bitmap.getWidth() - bounds.width()) / 2,                  (bitmap.getHeight() + bounds.height()) / 2);    }    //图片上绘制文字    private static Bitmap drawTextToBitmap(Context context, Bitmap bitmap, String text,            Paint paint, Rect bounds, int paddingLeft, int paddingTop) {        android.graphics.Bitmap.Config bitmapConfig = bitmap.getConfig();        paint.setDither(true); // 获取跟清晰的图像采样        paint.setFilterBitmap(true);// 过滤一些        if (bitmapConfig == null) {            bitmapConfig = android.graphics.Bitmap.Config.ARGB_8888;        }        bitmap = bitmap.copy(bitmapConfig, true);        Canvas canvas = new Canvas(bitmap);        canvas.drawText(text, paddingLeft, paddingTop, paint);        return bitmap;    }    /**     * 缩放图片     * @param src     * @param w     * @param h     * @return     */    public static Bitmap scaleWithWH(Bitmap src, double w, double h) {        if (w == 0 || h == 0 || src == null) {            return src;        } else {            // 记录src的宽高            int width = src.getWidth();            int height = src.getHeight();            // 创建一个matrix容器            Matrix matrix = new Matrix();            // 计算缩放比例            float scaleWidth = (float) (w / width);            float scaleHeight = (float) (h / height);            // 开始缩放            matrix.postScale(scaleWidth, scaleHeight);            // 创建缩放后的图片            return Bitmap.createBitmap(src, 0, 0, width, height, matrix, true);        }    }    /**     * dip转pix     * @param context     * @param dp     * @return     */    public static int dp2px(Context context, float dp) {         final float scale = context.getResources().getDisplayMetrics().density;         return (int) (dp * scale + 0.5f);     } }

使用方法如下：

添加一个布局，上面是原始图片，下面是添加水印后的图片

(本文出自水寒的CSDN博客：）

在Activity中获取到ImageView对象，并且获取Bitmap对象，对Bitmap进行canva绘图，添加水印：

/** * 图片工具类 * @author 水寒 * 欢迎访问水寒的个人博客：http://www.sunhome.org.cn * */public class MainActivity extends Activity {
         private ImageView mSourImage;    private ImageView mWartermarkImage;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initView();    }    private void initView(){        mSourImage = (ImageView) findViewById(R.id.sour_pic);        mWartermarkImage = (ImageView) findViewById(R.id.wartermark_pic);        Bitmap sourBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.sour_pic);        mSourImage.setImageBitmap(sourBitmap);        Bitmap waterBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.weixin);        Bitmap watermarkBitmap = ImageUtil.createWaterMaskCenter(sourBitmap, waterBitmap);        watermarkBitmap = ImageUtil.createWaterMaskLeftBottom(this, watermarkBitmap, waterBitmap, 0, 0);        watermarkBitmap = ImageUtil.createWaterMaskRightBottom(this, watermarkBitmap, waterBitmap, 0, 0);        watermarkBitmap = ImageUtil.createWaterMaskLeftTop(this, watermarkBitmap, waterBitmap, 0, 0);        watermarkBitmap = ImageUtil.createWaterMaskRightTop(this, watermarkBitmap, waterBitmap, 0, 0);        Bitmap textBitmap = ImageUtil.drawTextToLeftTop(this, watermarkBitmap, "左上角", 16, Color.RED, 0, 0);        textBitmap = ImageUtil.drawTextToRightBottom(this, textBitmap, "右下角", 16, Color.RED, 0, 0);        textBitmap = ImageUtil.drawTextToRightTop(this, textBitmap, "右上角", 16, Color.RED, 0, 0);        textBitmap = ImageUtil.drawTextToLeftBottom(this, textBitmap, "左下角", 16, Color.RED, 0, 0);        textBitmap = ImageUtil.drawTextToCenter(this, textBitmap, "中间", 16, Color.RED);        mWartermarkImage.setImageBitmap(textBitmap);    }}