Android中Bitmap和Drawable，等相关内容

 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

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

2、Bitmap → byte[]

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

3、byte[] → Bitmap

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

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;
    }

  5、将Drawable转化为Bitmap

 

    public static Bitmap getRoundedCornerBitmap(Bitmap bitmap, float roun         dPx) {
        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;
    }

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;
    }

 7、获得带倒影的图片

 

    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

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

    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);
    }

// 获取bitmap占用的字节数
protected int sizeOf(Bitmap data) {
  if (Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB_MR1) {
     return data.getRowBytes() * data.getHeight();
  } else {
     return data.getByteCount();
  }
}

 // 3.以RGB_565方式读入图片
 public Bitmap readBitMap(Context context, int resId) {
   BitmapFactory.Options opt = new BitmapFactory.Options();
   opt.inPreferredConfig = Bitmap.Config.RGB_565;
   opt.inPurgeable = true;
   opt.inInputShareable = true;
   // 获取资源图片
   InputStream is = context.getResources().openRawResource(resId);
   return BitmapFactory.decodeStream(is, null, opt);
  }

// 4.获取ImageView和其中drawable的大小
// 获取ImageView和其中drawable大小需在onWindowFocusChanged获取，在oncreate中返回的结果是0
 public void onWindowFocusChanged(boolean hasFocus) {
   ImageView imageView = (ImageView) findViewById(R.id.test1);
   Log.v("Testresult", "width= " + imageView.getWidth() + " height= "
          + imageView.getHeight());
   Log.v("Testresult", "drawawidth= "
        + imageView.getDrawable().getBounds().width()
        + " drawableheight= "
        + imageView.getDrawable().getBounds().height());
 }