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

 Resourcesres=getResources();
 Bitmapbmp=BitmapFactory.decodeResource(res,R.drawable.icon);

2、Bitmap → byte[]

 publicbyte[]Bitmap2Bytes(Bitmapbm){
 ByteArrayOutputStreambaos=newByteArrayOutputStream();
 bm.compress(Bitmap.CompressFormat.PNG,100,baos);
 returnbaos.toByteArray();
 }

3、byte[] → Bitmap

 publicBitmapBytes2Bimap(byte[]b){
 if(b.length!=0){
 returnBitmapFactory.decodeByteArray(b,0,b.length);
 }else{
 returnnull;
 }
 }

4、Bitmap缩放

 publicstaticBitmapzoomBitmap(Bitmapbitmap,intwidth,intheight){
 intw=bitmap.getWidth();
 inth=bitmap.getHeight();
 Matrixmatrix=newMatrix();
 floatscaleWidth=((float)width/w);
 floatscaleHeight=((float)height/h);
 matrix.postScale(scaleWidth,scaleHeight);
 Bitmapnewbmp=Bitmap.createBitmap(bitmap,0,0,w,h,matrix,true);
 returnnewbmp;
 }

5、将Drawable转化为Bitmap

 publicstaticBitmapdrawableToBitmap(Drawabledrawable){
 //取drawable的长宽
 intw=drawable.getIntrinsicWidth();
 inth=drawable.getIntrinsicHeight();

 //取drawable的颜色格式
 Bitmap.Configconfig=drawable.getOpacity()!=PixelFormat.OPAQUE?Bitmap.Config.ARGB_8888
 :Bitmap.Config.RGB_565;
 //建立对应bitmap
 Bitmapbitmap=Bitmap.createBitmap(w,h,config);
 //建立对应bitmap的画布
 Canvascanvas=newCanvas(bitmap);
 drawable.setBounds(0,0,w,h);
 //把drawable内容画到画布中
 drawable.draw(canvas);
 returnbitmap;
 }

6、获得圆角图片

 publicstaticBitmapgetRoundedCornerBitmap(Bitmapbitmap,floatroundPx){
 intw=bitmap.getWidth();
 inth=bitmap.getHeight();
 Bitmapoutput=Bitmap.createBitmap(w,h,Config.ARGB_8888);
 Canvascanvas=newCanvas(output);
 finalintcolor=0xff424242;
 finalPaintpaint=newPaint();
 finalRectrect=newRect(0,0,w,h);
 finalRectFrectF=newRectF(rect);
 paint.setAntiAlias(true);
 canvas.drawARGB(0,0,0,0);
 paint.setColor(color);
 canvas.drawRoundRect(rectF,roundPx,roundPx,paint);
 paint.setXfermode(newPorterDuffXfermode(Mode.SRC_IN));
 canvas.drawBitmap(bitmap,rect,rect,paint);

 returnoutput;
 }

7、获得带倒影的图片

 publicstaticBitmapcreateReflectionImageWithOrigin(Bitmapbitmap){
 finalintreflectionGap=4;
 intw=bitmap.getWidth();
 inth=bitmap.getHeight();

 Matrixmatrix=newMatrix();
 matrix.preScale(1,-1);

 BitmapreflectionImage=Bitmap.createBitmap(bitmap,0,h/2,w,
 h/2,matrix,false);

 BitmapbitmapWithReflection=Bitmap.createBitmap(w,(h+h/2),
 Config.ARGB_8888);

 Canvascanvas=newCanvas(bitmapWithReflection);
 canvas.drawBitmap(bitmap,0,0,null);
 PaintdeafalutPaint=newPaint();
 canvas.drawRect(0,h,w,h+reflectionGap,deafalutPaint);

 canvas.drawBitmap(reflectionImage,0,h+reflectionGap,null);

 Paintpaint=newPaint();
 LinearGradientshader=newLinearGradient(0,bitmap.getHeight(),0,
 bitmapWithReflection.getHeight()+reflectionGap,0x70ffffff,
 0x00ffffff,TileMode.CLAMP);
 paint.setShader(shader);
 //SettheTransfermodetobeporterduffanddestinationin
 paint.setXfermode(newPorterDuffXfermode(Mode.DST_IN));
 //Drawarectangleusingthepaintwithourlineargradient
 canvas.drawRect(0,h,w,bitmapWithReflection.getHeight()
 +reflectionGap,paint);

 returnbitmapWithReflection;
 }

三、Drawable

1、Bitmap转换成Drawable

 Bitmapbm=xxx;//xxx根据你的情况获取
 BitmapDrawablebd=newBitmapDrawable(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

 publicstaticDrawablezoomDrawable(Drawabledrawable,intw,inth){
 intwidth=drawable.getIntrinsicWidth();
 intheight=drawable.getIntrinsicHeight();
 //drawable转换成bitmap
 Bitmapoldbmp=drawableToBitmap(drawable);
 //创建操作图片用的Matrix对象
 Matrixmatrix=newMatrix();
 //计算缩放比例
 floatsx=((float)w/width);
 floatsy=((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
 Bitmapnewbmp=Bitmap.createBitmap(oldbmp,0,0,width,height,
 matrix,true);
 returnnewBitmapDrawable(newbmp);
 }