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

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缩放

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 

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、获得带倒影的图片

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

1     public 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     }