Android中Bitmap和Drawable

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); 
    }