Android中Bitmap,byte[],Drawable相互转化

转载自：http://blog.csdn.net/xidiancoder/article/details/51649465

在surfaceview中结合Camera获取到摄像头图像，这段代码是我程序中的一部分

    @Override    public void onPreviewFrame(final byte[] data, Camera camera) {        camera.setPreviewCallback(null);        if (mCamera == null)            return;        Camera.Parameters parameters = camera.getParameters();        int width = parameters.getPreviewSize().width;        int height = parameters.getPreviewSize().height;        YuvImage yuv = new YuvImage(data, parameters.getPreviewFormat(), width, height, null);        ByteArrayOutputStream out = new ByteArrayOutputStream();        yuv.compressToJpeg(new Rect(0, 0, width, height), 50, out);        byte[] bytes = out.toByteArray();        final Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);        this.mCamera.setPreviewCallback(this);    }
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现在对三者具体如何互相转换做一说明：

准备：概念说明

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 ,图像矩阵

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1.从resources中获取Bitmap

 Resources res = getResources(); Bitmap bmp = BitmapFactory.decodeResource(res, R.drawable.icon);
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2.Bitmap → byte[]

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

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

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;    }
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5.将Drawable转化为Bitmap

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;    }
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6.获得圆角图片

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;    }
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7.Bitmap转换成Drawable

 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。
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8.Drawable缩放

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);    }
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