Bitmap和Drawable一些特殊用法整理

Bitmap

1、從資源中獲取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縮放

    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、將Drawable轉化爲Bitmap

    public static Bitmap drawableToBitmap(Drawable drawable) {  
            // 取 drawable 的長寬  
            int w = drawable.getIntrinsicWidth();  
            int h = drawable.getIntrinsicHeight();  
      
            // 取 drawable 的顏色格式  
            Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888  
                    : Bitmap.Config.RGB_565;  
            // 建立對應 bitmap  
            Bitmap bitmap = Bitmap.createBitmap(w, h, config);  
            // 建立對應 bitmap 的畫布  
            Canvas canvas = new Canvas(bitmap);  
            drawable.setBounds(0, 0, w, h);  
            // 把 drawable 內容畫到畫布中  
            drawable.draw(canvas);  
            return bitmap;  
        }  

6、獲得圓角圖片

    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、獲得帶倒影的圖片

    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;  
    }  

Drawable

1、Bitmap轉換成Drawable

Bitmap bm=xxx; //xxx根據你的情況獲取  
BitmapDrawable bd= new BitmapDrawable(getResource(), bm);   
因爲BtimapDrawable是Drawable的子類，最終直接使用bd對象即可。 

2、Drawable縮放

    public static Drawable zoomDrawable(Drawable drawable, int w, int h) {  
        int width = drawable.getIntrinsicWidth();  
        int height = drawable.getIntrinsicHeight();  
        // drawable轉換成bitmap  
        Bitmap oldbmp = drawableToBitmap(drawable);  
        // 創建操作圖片用的Matrix對象  
        Matrix matrix = new Matrix();  
        // 計算縮放比例  
        float sx = ((float) w / width);  
        float sy = ((float) h / height);  
        // 設置縮放比例  
        matrix.postScale(sx, sy);  
        // 建立新的bitmap，其內容是對原bitmap的縮放後的圖  
        Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,  
                matrix, true);  
        return new BitmapDrawable(newbmp);  
    }