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 bitmap10         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 in28         paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));29         // Draw a rectangle using the paint with our linear gradient30         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     }