Android中Bitmap和Drawable [轉]

一、相關概念

1、Drawable就是一個可畫的對象，其可能是一張位圖（BitmapDrawable），也可能是一個圖形（ShapeDrawable），還有可能是一個圖層（LayerDrawable），我們根據畫圖的需求，創建相應的可畫對象

2、Canvas畫布，繪圖的目的區域，用於繪圖

3、Bitmap位圖，用於圖的處理

4、Matrix矩陣

二、Bitmap
1、從資源中獲取Bitmap
Java代碼 收藏代碼

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

2、Bitmap → byte[]
Java代碼 收藏代碼

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

3、byte[] → Bitmap
Java代碼 收藏代碼

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

4、Bitmap縮放
Java代碼 收藏代碼

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
Java代碼 收藏代碼

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
Java代碼 收藏代碼

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
Java代碼 收藏代碼

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轉換成Drawable
Java代碼 收藏代碼

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
Java代碼 收藏代碼

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);  
}