Android中Bitmap,byte[],Drawable互相轉化

一、相關概念

1、Drawable就是一個可畫的對象，其可能是一張位圖（BitmapDrawable），也可能是一個圖形（ShapeDrawable），還有可能是一個圖層（LayerDrawable），我們根據畫圖的需求，建立相應的可畫對象      

2、Canvas畫布，繪圖的目的區域，用于繪圖      

3、Bitmap位圖，用于圖的處理      

4、Matrix矩陣      

二、Bitmap

1、從資源中擷取Bitmap

1     Resources res = getResources();      

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

2、Bitmap → byte[]

1     public byte[] Bitmap2Bytes(Bitmap bm) {      

2         ByteArrayOutputStream baos = new ByteArrayOutputStream();      

3         bm.compress(Bitmap.CompressFormat.PNG, 100, baos);      

4         return baos.toByteArray();      

5     }      

3、byte[] → Bitmap

1     public 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縮放

1     public 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轉化為Bitmap

1 public static Bitmap drawableToBitmap(Drawable drawable) {      

2         // 取 drawable 的長寬      

3         int w = drawable.getIntrinsicWidth();      

4         int h = drawable.getIntrinsicHeight();      

5      

6         // 取 drawable 的顔色格式      

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

8                 : Bitmap.Config.RGB_565;      

9         // 建立對應 bitmap      

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

11         // 建立對應 bitmap 的畫布      

12         Canvas canvas = new Canvas(bitmap);      

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

14         // 把 drawable 内容畫到畫布中      

15         drawable.draw(canvas);      

16         return bitmap;      

17     }      

6、獲得圓角圖檔 

1     public 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、獲得帶倒影的圖檔

1     public 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轉換成Drawable

1 Bitmap bm=xxx; //xxx根據你的情況擷取      

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

3 因為BtimapDrawable是Drawable的子類，最終直接使用bd對象即可。      

2、Drawable縮放

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

2         int width = drawable.getIntrinsicWidth();      

3         int height = drawable.getIntrinsicHeight();      

4         // drawable轉換成bitmap      

5         Bitmap oldbmp = drawableToBitmap(drawable);      

6         // 建立操作圖檔用的Matrix對象      

7         Matrix matrix = new Matrix();      

8         // 計算縮放比例      

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

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

11         // 設定縮放比例      

12         matrix.postScale(sx, sy);      

13         // 建立新的bitmap，其内容是對原bitmap的縮放後的圖      

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

15                 matrix, true);      

16         return new BitmapDrawable(newbmp);      

17     }