Android中Bitmap和Drawable詳解

Android中Bitmap和Drawable詳解

  
 

 

一、相關概念

 

1、Drawable就是一個可畫的對象，其可能是一張位元影像（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，建立相應的可畫對象

2、Canvas畫布，繪圖的目的地區，用於繪圖

3、Bitmap位元影像，用於圖的處理

4、Matrix矩陣

二、Bitmap1、從資源中擷取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轉化為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;    }

三、Drawable1、Bitmap轉換成Drawable

Bitmap bm=xxx; //xxx根據你的情況擷取BitmapDrawable bd= new BitmapDrawable(getResource(), bm); 因為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);        // 建立操作圖片用的Matrix對象        Matrix matrix = new Matrix();        // 計算縮放比例        float sx = ((float) w / width);        float sy = ((float) h / height);        // 設定縮放比例        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);    }