android Bitmap、Drawable、byte[]相互转换

Drawable -作为Android平下通用的图形对象，它可以装载常用格式的图像，比如GIF、PNG、JPG，当然也支持BMP，当然还提供一些高级的可视化对象，比如渐变、图形等。

Bitmap -称作位图，一般位图的文件格式后缀为bmp，当然编码器也有很多如RGB565、RGB888。作为一种像素的显示对象执行效率高，但是缺点也很明显存储效率低。我们理解为一种存储对象比较好。

android在处理一写图片资源的时候，会进行一些类型的转换，现在有空整理一下：

1、Drawable → Bitmap 的简单方法

Drawable d = XXX;

BitmapDrawable bd =(BitmapDrawable)d;

Bitmap b =bd.getBitmap();

可简化为：((BitmapDrawable)res.getDrawable(R.drawable.youricon)).getBitmap();

Java代码
public static Bitmap drawableToBitmap(Drawable drawable){

Bitmap bitmap= Bitmap
.createBitmap(
drawable.getIntrinsicWidth(),
drawable.getIntrinsicHeight(),
drawable.getOpacity() != PixelFormat.OPAQUE ?Bitmap.Config.ARGB_8888 : Bitmap.Config.RGB_565); //按指定参数创建一个空的Bitmap对象
Canvas canvas= new Canvas(bitmap);
//canvas.setBitmap(bitmap);
drawable.setBounds(0,0, drawable.getIntrinsicWidth(),drawable.getIntrinsicHeight());
drawable.draw(canvas);
returnbitmap;
}

3.Bitmap→Drawable 的简单方法
BitmapDrawable bitmapDrawable= (BitmapDrawable)bitmap;
Drawable drawable = (Drawable)bitmapDrawable;

Bitmap bitmap = newBitmap (...);
Drawable drawable = new BitmapDrawable(bitmap);

3、从资源中获取Bitmap
Java代码
Bitmap bmp=BitmapFactory.decodeResource(getResources(),R.drawable.pic);

4、Bitmap → Byte[]
Java代码
private byte[] Bitmap2Bytes(Bitmapbm){
ByteArrayOutputStream baos =new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
returnbaos.toByteArray();
}

5、 byte[] → Bitmap
Java代码
private Bitmap Bytes2Bimap(byte[]b){
if(b.length!=0){
returnBitmapFactory.decodeByteArray(b, 0,b.length);
}
else{
returnnull;
}
}

6、保存Bmp文件
static boolean saveBitmap2file(Bitmap bmp,String filename){
CompressFormat format= Bitmap.CompressFormat.JPEG;
int quality = 100;
OutputStream stream = null;
try {
stream = new FileOutputStream("/sdcard/" + filename);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
return bmp.compress(format, quality, stream);
}
7、将图片按自己的要求缩放
// 图片源
Bitmap bm = BitmapFactory.decodeStream(getResources().openRawResource(R.drawable.dog));
// 获得图片的宽高
int width = bm.getWidth();
int height = bm.getHeight();
// 设置想要的大小
int newWidth = 320;
int newHeight = 480;
// 计算缩放比例
float scaleWidth = ((float) newWidth) / width;
float scaleHeight = ((float) newHeight) / height;
// 取得想要缩放的matrix参数
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
// 得到新的图片
Bitmap newbm = Bitmap.createBitmap(bm, 0, 0, width, height, matrix,
true);
// 放在画布上
canvas.drawBitmap(newbm, 0, 0, paint);
相关知识链接：http://www.eoeandroid.com/thread-3162-1-1.html
8、//放大缩小图片
public static Bitmap zoomBitmap(Bitmap bitmap,int w,int h){
//获得原始图片宽高
int width = bitmap.getWidth();
int height = bitmap.getHeight();
Matrix matrix = new Matrix();
//计算缩放比（目标宽高/原始宽高）
float scaleWidht = ((float)w / width);
float scaleHeight = ((float)h / height);
matrix.postScale(scaleWidht, scaleHeight);
Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix,
true);
return newbmp;
}
9、//将Drawable转化为Bitmap
public static Bitmap drawableToBitmap(Drawable drawable){

int width = drawable.getIntrinsicWidth();
int height = drawable.getIntrinsicHeight();
Bitmapbitmap=Bitmap.createBitmap(width,height,
drawable.getOpacity()!=PixelFormat.OPAQUE?Bitmap.Config.ARGB_8888
:Bitmap.Config.RGB_565);//创建一个指定高、宽的可变的Bitmap图像
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0,0,width,height);
drawable.draw(canvas);
return bitmap;
}
10、//获得圆角图片的方法
public static Bitmap getRoundedCornerBitmap(Bitmap bitmap,float roundPx){
Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap
.getHeight(), Config.ARGB_8888);
Canvas canvas = new Canvas(output);
final int color = 0xff424242;
final Paint paint = new Paint();
final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
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;
}
11、//获得带倒影的图片方法
public static Bitmap createReflectionImageWit hOrigin(Bitmap bitmap){
final int reflectionGap = 4;
int width = bitmap.getWidth();
int height = bitmap.getHeight();
Matrix matrix = new Matrix();
matrix.preScale(1,-1);
Bitmap reflectionImage = Bitmap.createBitmap(bitmap,
0, height/2, width, height/2, matrix, false);
BitmapbitmapWithReflection=Bitmap.createBitmap(width,(height+height/2),
Config.ARGB_8888);
Canvas canvas = new Canvas(bitmapWithReflection);
canvas.drawBitmap(bitmap, 0, 0, null);
Paint deafalutPaint = new Paint();
canvas.drawRect(0, height,width,height + reflectionGap,
deafalutPaint);
canvas.drawBitmap(reflectionImage, 0, height + 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, height, width, bitmapWithReflection.getHeight()
+ reflectionGap, paint);
return bitmapWithReflection;
}
}
12、图片水印的生成方法
生成水印的过程。其实分为三个环节：第一，载入原始图片；第二，载入水印图片；第三，保存新的图片。

private Bitmap createBitmap(Bitmap src, Bitmap watermark)
{
String tag ="createBitmap";
Log.d( tag, "create a new bitmap");
if( src == null )
{
return null;
}

int w = src.getWidth();
int h = src.getHeight();
int ww =watermark.getWidth();
int wh =watermark.getHeight();
//create the new blankbitmap
Bitmap newb = Bitmap.createBitmap( w, h, Config.ARGB_8888);//创建一个新的和SRC长度宽度一样的位图
Canvas cv = new Canvas( newb);
//draw src into
cv.drawBitmap( src, 0, 0, null );//在0，0坐标开始画入src
//draw watermark into
cv.drawBitmap( watermark, w - ww + 5, h - wh + 5, null);//在src的右下角画入水印
//save all clip
cv.save( Canvas.ALL_SAVE_FLAG);//保存
//store
cv.restore();//存储
return newb;
}
13、bitmap的用法小结
BitmapFactory.Options option = new BitmapFactory.Options();
option.inSampleSize = 2; //将图片设为原来宽高的1/2，防止内存溢出
Bitmap bm = BitmapFactory.decodeFile("",option);//文件流
URL url = new URL("");
InputStream is = url.openStream();
Bitmap bm = BitmapFactory.decodeStream(is);
android:scaleType：控制图片如何resized/moved来匹对ImageView的size。ImageView.ScaleType /
android:scaleType值的意义区别：
CENTER /center 按图片的原来size居中显示，当图片长/宽超过View的长/宽，则截取图片的居中部分
显示
CENTER_CROP / centerCrop 按比例扩大图片的size居中显示，使得图片长(宽)等于或大于View的长
(宽)
CENTER_INSIDE / centerInside 将图片的内容完整居中显示，通过按比例缩小或原来的size使得图片
长/宽等于或小于View的长/宽
Generated by Foxit PDF Creator ? Foxit Software
http://www.foxitsoftware.com For evaluation only.
FIT_CENTER / fitCenter 把图片按比例扩大/缩小到View的宽度，居中显示
FIT_END / fitEnd 把图片按比例扩大/缩小到View的宽度，显示在View的下部分位置
FIT_START / fitStart 把图片按比例扩大/缩小到View的宽度，显示在View的上部分位置
FIT_XY / fitXY 把图片不按比例扩大/缩小到View的大小显示
MATRIX / matrix 用矩阵来绘制，动态缩小放大图片来显示。

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