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();

Bitmap bitmap = 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 createReflectionImageWithOrigin(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);

Bitmap bitmapWithReflection = 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

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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。