drawable與bitmap轉換

轉載自：http://dyh7077063.iteye.com/blog/970672

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 bitmapBitmap 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 inpaint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));// Draw a rectangle using the paint with our linear gradientcanvas.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bitmapBitmap 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);}

Drawable to Bitmap 應該這麼寫

/**      * Drawable 轉 bitmap      * @param drawable      * @return      */      public static Bitmap drawable2Bitmap(Drawable drawable){          if(drawable instanceof BitmapDrawable){              return ((BitmapDrawable)drawable).getBitmap() ;          }else if(drawable instanceof NinePatchDrawable){              Bitmap bitmap = Bitmap                      .createBitmap(                              drawable.getIntrinsicWidth(),                              drawable.getIntrinsicHeight(),                              drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888                                      : Bitmap.Config.RGB_565);              Canvas canvas = new Canvas(bitmap);              drawable.setBounds(0, 0, drawable.getIntrinsicWidth(),                      drawable.getIntrinsicHeight());              drawable.draw(canvas);              return bitmap;          }else{              return null ;          }      }