Android中Bitmap和Drawable用法詳解

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、Bitmap
1、從資源中擷取Bitmap

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

2、Bitmap → byte[]

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

3、byte[] → Bitmap

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

Bitmap縮放

代碼如下

複製代碼

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轉化為Bitmap

代碼如下

複製代碼

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;     } 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; }

6、獲得圓角圖片

代碼如下

複製代碼

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

代碼如下	複製代碼
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

代碼如下

複製代碼

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);     // 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); }