Android中Bitmap和Drawable

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 bitmapBitmap 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 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、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bitmapBitmap 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);}