Android中Bitmap和Drawable [转]

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
Java代码 收藏代码

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

2、Bitmap → byte[]
Java代码 收藏代码

public byte[] Bitmap2Bytes(Bitmap bm) {      ByteArrayOutputStream baos = new ByteArrayOutputStream();      bm.compress(Bitmap.CompressFormat.PNG, 100, baos);      return baos.toByteArray();  }  

3、byte[] → Bitmap
Java代码 收藏代码

public Bitmap Bytes2Bimap(byte[] b) {      if (b.length != 0) {          return BitmapFactory.decodeByteArray(b, 0, b.length);      } else {          return null;      }  }  

4、Bitmap缩放
Java代码 收藏代码

public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) {      int w = bitmap.getWidth();      int h = bitmap.getHeight();      Matrix matrix = new Matrix();      float scaleWidth = ((float) width / w);      float scaleHeight = ((float) height / h);      matrix.postScale(scaleWidth, scaleHeight);      Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);      return newbmp;  }  

5、将Drawable转化为Bitmap
Java代码 收藏代码

public static Bitmap drawableToBitmap(Drawable drawable) {          // 取 drawable 的长宽          int w = drawable.getIntrinsicWidth();          int h = drawable.getIntrinsicHeight();          // 取 drawable 的颜色格式          Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888                  : Bitmap.Config.RGB_565;          // 建立对应 bitmap          Bitmap bitmap = Bitmap.createBitmap(w, h, config);          // 建立对应 bitmap 的画布          Canvas canvas = new Canvas(bitmap);          drawable.setBounds(0, 0, w, h);          // 把 drawable 内容画到画布中          drawable.draw(canvas);          return bitmap;      }  

6、获得圆角图片
Java代码 收藏代码

public static Bitmap getRoundedCornerBitmap(Bitmap bitmap, float roundPx) {      int w = bitmap.getWidth();      int h = bitmap.getHeight();      Bitmap output = Bitmap.createBitmap(w, h, Config.ARGB_8888);      Canvas canvas = new Canvas(output);      final int color = 0xff424242;      final Paint paint = new Paint();      final Rect rect = new Rect(0, 0, w, h);      final RectF rectF = new RectF(rect);      paint.setAntiAlias(true);      canvas.drawARGB(0, 0, 0, 0);      paint.setColor(color);      canvas.drawRoundRect(rectF, roundPx, roundPx, paint);      paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));      canvas.drawBitmap(bitmap, rect, rect, paint);      return output;  }  

7、获得带倒影的图片
Java代码 收藏代码

public static Bitmap createReflectionImageWithOrigin(Bitmap bitmap) {      final int reflectionGap = 4;      int w = bitmap.getWidth();      int h = bitmap.getHeight();      Matrix matrix = new Matrix();      matrix.preScale(1, -1);      Bitmap reflectionImage = Bitmap.createBitmap(bitmap, 0, h / 2, w,              h / 2, matrix, false);      Bitmap bitmapWithReflection = Bitmap.createBitmap(w, (h + h / 2),              Config.ARGB_8888);      Canvas canvas = new Canvas(bitmapWithReflection);      canvas.drawBitmap(bitmap, 0, 0, null);      Paint deafalutPaint = new Paint();      canvas.drawRect(0, h, w, h + reflectionGap, deafalutPaint);      canvas.drawBitmap(reflectionImage, 0, h + reflectionGap, null);      Paint paint = new Paint();      LinearGradient shader = new LinearGradient(0, bitmap.getHeight(), 0,              bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff,              0x00ffffff, TileMode.CLAMP);      paint.setShader(shader);      // Set the Transfer mode to be porter duff and destination in      paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));      // Draw a rectangle using the paint with our linear gradient      canvas.drawRect(0, h, w, bitmapWithReflection.getHeight()              + reflectionGap, paint);      return bitmapWithReflection;  }  

三、Drawable
1、Bitmap转换成Drawable
Java代码 收藏代码

Bitmap bm=xxx; //xxx根据你的情况获取  BitmapDrawable bd= new BitmapDrawable(getResource(), bm);   因为BtimapDrawable是Drawable的子类，最终直接使用bd对象即可。  

2、Drawable缩放
Java代码 收藏代码

public static Drawable zoomDrawable(Drawable drawable, int w, int h) {      int width = drawable.getIntrinsicWidth();      int height = drawable.getIntrinsicHeight();      // drawable转换成bitmap      Bitmap oldbmp = drawableToBitmap(drawable);      // 创建操作图片用的Matrix对象      Matrix matrix = new Matrix();      // 计算缩放比例      float sx = ((float) w / width);      float sy = ((float) h / height);      // 设置缩放比例      matrix.postScale(sx, sy);      // 建立新的bitmap，其内容是对原bitmap的缩放后的图      Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,              matrix, true);      return new BitmapDrawable(newbmp);  }