Android中Bitmap byte[] Drawable相互转化

一、相关概念

1、Drawable就是一个可画的对象，其可能是一张位图（BitmapDrawable），也可能是一个图形（ShapeDrawable），还有可能是一个图层（LayerDrawable），我们根据画图的需求，创建相应的可画对象

2、Canvas画布，绘图的目的区域，用于绘图

3、Bitmap位图，用于图的处理

4、Matrix矩阵

二、Bitmap

1、从资源中获取Bitmap

1Resources res = getResources();

2Bitmap bmp = BitmapFactory.decodeResource(res, R.drawable.icon);

2、Bitmap → byte[]

1public byte[] Bitmap2Bytes(Bitmap bm) {

2 ByteArrayOutputStream baos = new ByteArrayOutputStream();

3 press(pressFormat.PNG, 100, baos);

4 return baos.toByteArray();

5}

3、byte[] → Bitmap

1public Bitmap Bytes2Bimap(byte[] b) {

2 if (b.length != 0) {

3 return BitmapFactory.decodeByteArray(b, 0, b.length);

4 } else {

5 return null;

6 }

7}

4、Bitmap缩放

1public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) {

2 int w = bitmap.getWidth();

3 int h = bitmap.getHeight();

4 Matrix matrix = new Matrix();

5 float scaleWidth = ((float) width / w);

6 float scaleHeight = ((float) height / h);

7 matrix.postScale(scaleWidth, scaleHeight);

8 Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);

9 return newbmp;

10}

5、将Drawable转化为Bitmap

1 public static Bitmap drawableToBitmap(Drawable drawable) {

2 // 取 drawable 的长宽

3 int w = drawable.getIntrinsicWidth();

4 int h = drawable.getIntrinsicHeight();

5

6 // 取 drawable 的颜色格式

7 Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888

8 : Bitmap.Config.RGB_565;

9 // 建立对应 bitmap

10 Bitmap bitmap = Bitmap.createBitmap(w, h, config);

11 // 建立对应 bitmap 的画布

12 Canvas canvas = new Canvas(bitmap);

13 drawable.setBounds(0, 0, w, h);

14 // 把 drawable 内容画到画布中

15 drawable.draw(canvas);

16 return bitmap;

17}

6、获得圆角图片

1public static Bitmap getRoundedCornerBitmap(Bitmap bitmap, float roundPx) {

2 int w = bitmap.getWidth();

3 int h = bitmap.getHeight();

4 Bitmap output = Bitmap.createBitmap(w, h, Config.ARGB_8888);

5 Canvas canvas = new Canvas(output);

6 final int color = 0xff424242;

7 final Paint paint = new Paint();

8 final Rect rect = new Rect(0, 0, w, h);

9 final RectF rectF = new RectF(rect);

10 paint.setAntiAlias(true);

11 canvas.drawARGB(0, 0, 0, 0);

12 paint.setColor(color);

13 canvas.drawRoundRect(rectF, roundPx, roundPx, paint);

14 paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));

15 canvas.drawBitmap(bitmap, rect, rect, paint);

16

17 return output;

18}

7、获得带倒影的图片

1public static Bitmap createReflectionImageWithOrigin(Bitmap bitmap) {

2 final int reflectionGap = 4;

3 int w = bitmap.getWidth();

4 int h = bitmap.getHeight();

5

6 Matrix matrix = new Matrix();

7 matrix.preScale(1, -1);

8

9 Bitmap reflectionImage = Bitmap.createBitmap(bitmap, 0, h / 2, w,

10 h / 2, matrix, false);

11

12 Bitmap bitmapWithReflection = Bitmap.createBitmap(w, (h + h / 2),

13 Config.ARGB_8888);

14

15 Canvas canvas = new Canvas(bitmapWithReflection);

16 canvas.drawBitmap(bitmap, 0, 0, null);

17 Paint deafalutPaint = new Paint();

18 canvas.drawRect(0, h, w, h + reflectionGap, deafalutPaint);

19

20 canvas.drawBitmap(reflectionImage, 0, h + reflectionGap, null);

21

22 Paint paint = new Paint();

23 LinearGradient shader = new LinearGradient(0, bitmap.getHeight(), 0,

24 bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff,

25 0x00ffffff, TileMode.CLAMP);

26 paint.setShader(shader);

27 // Set the Transfer mode to be porter duff and destination in

28 paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));

29 // Draw a rectangle using the paint with our linear gradient

30 canvas.drawRect(0, h, w, bitmapWithReflection.getHeight()

31 + reflectionGap, paint);

32

33 return bitmapWithReflection;

34}

三、Drawable

1、Bitmap转换成Drawable

1 Bitmap bm=xxx; //xxx根据你的情况获取

2 BitmapDrawable bd= new BitmapDrawable(getResource(), bm);

3 因为BtimapDrawable是Drawable的子类，最终直接使用bd对象即可。

2、Drawable缩放

1public static Drawable zoomDrawable(Drawable drawable, int w, int h) {

2 int width = drawable.getIntrinsicWidth();

3 int height = drawable.getIntrinsicHeight();

4 // drawable转换成bitmap

5 Bitmap oldbmp = drawableToBitmap(drawable);

6 // 创建操作图片用的Matrix对象

7 Matrix matrix = new Matrix();

8 // 计算缩放比例

9 float sx = ((float) w / width);

10 float sy = ((float) h / height);

11 // 设置缩放比例

12 matrix.postScale(sx, sy);

13 // 建立新的bitmap，其内容是对原bitmap的缩放后的图

14 Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,

15 matrix, true);

16 return new BitmapDrawable(newbmp);

17}

本文转自dyh7077063的博客/blog/970672