[轉載]Android中Bitmap和Drawable

1、相關概念

一、Drawable就是一個可畫的對象，其多是一張位圖（BitmapDrawable），也多是一個圖形（ShapeDrawable），還有多是一個圖層（LayerDrawable），咱們根據畫圖的需求，建立相應的可畫對象

二、Canvas畫布，繪圖的目的區域，用於繪圖

三、Bitmap位圖，用於圖的處理

四、Matrix矩陣

2、Bitmap

一、從資源中獲取Bitmap

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

 

二、Bitmap → byte[]

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

 三、byte[] → Bitmap

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

四、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;
}

  五、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;
        // 創建對應 bitmap
        Bitmap bitmap = Bitmap.createBitmap(w, h, config);
        // 創建對應 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;
    }

六、得到圓角圖片 

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;
}

 七、得到帶倒影的圖片

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;
}

 3、Drawable

一、Bitmap轉換成Drawable

Bitmap bm=xxx; //xxx根據你的狀況獲取
BitmapDrawable bd= new BitmapDrawable(getResource(), bm);
由於BtimapDrawable是Drawable的子類，最終直接使用bd對象便可。

二、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);
    // 建立操做圖片用的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);
    // 創建新的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);
}