Android中Bitmap和Drawable互相转化

16lz 2021-01-24

Android中Bitmap和Drawable互相转化

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

Java代码

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

2、Bitmap → byte[]

Java代码

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

3、byte[] → Bitmap

Java代码

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

4、Bitmap缩放

Java代码

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

Java代码

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

Java代码

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

Java代码

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

Java代码

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

Java代码

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);
}

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