Android中Bitmap,byte[],Drawable相互转化

一、相关概念

1、Drawable就是一个可画的对象，其可能是一张位图（BitmapDrawable），也可能是一个图形（ShapeDrawable），还有可能是一个图层（LayerDrawable），我们根据画图的需求，创建相应的可画对象

2、Canvas画布，绘图的目的区域，用于绘图

3、Bitmap位图，用于图的处理

4、Matrix矩阵

二、Bitmap

1、从资源中获取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缩放

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、将Drawable转化为Bitmap

public static Bitmap drawableToBitmap(Drawable drawable) {         // 取 drawable 的长宽         int w = drawable.getIntrinsicWidth();         int h = drawable.getIntrinsicHeight();          // 取 drawable 的颜色格式         Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888                 : Bitmap.Config.RGB_565;         // 建立对应 bitmap         Bitmap bitmap = Bitmap.createBitmap(w, h, config);         // 建立对应 bitmap 的画布         Canvas canvas = new Canvas(bitmap);         drawable.setBounds(0, 0, w, h);         // 把 drawable 内容画到画布中         drawable.draw(canvas);         return bitmap;     } 

6、获得圆角图片

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、获得带倒影的图片

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、Drawable

1、Bitmap转换成Drawable

Bitmap bm=xxx; //xxx根据你的情况获取BitmapDrawable bd= new BitmapDrawable(getResource(), bm); 因为BtimapDrawable是Drawable的子类，最终直接使用bd对象即可。

2、Drawable缩放

public static Drawable zoomDrawable(Drawable drawable, int w, int h) {         int width = drawable.getIntrinsicWidth();         int height = drawable.getIntrinsicHeight();         // drawable转换成bitmap         Bitmap oldbmp = drawableToBitmap(drawable);         // 创建操作图片用的Matrix对象         Matrix matrix = new Matrix();         // 计算缩放比例         float sx = ((float) w / width);         float sy = ((float) h / height);         // 设置缩放比例         matrix.postScale(sx, sy);         // 建立新的bitmap，其内容是对原bitmap的缩放后的图         Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,                 matrix, true);         return new BitmapDrawable(newbmp);     }