android开发之Bitmap 、byte[] 、 Drawable之间的相互转换

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

1     Resources res = getResources();
2     Bitmap bmp = BitmapFactory.decodeResource(res, R.drawable.icon);

2、Bitmap → byte[]

1     public byte[] Bitmap2Bytes(Bitmap bm) {
2         ByteArrayOutputStream baos = new ByteArrayOutputStream();
3         bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
4         return baos.toByteArray();
5     }

3、byte[] → Bitmap

1     public Bitmap Bytes2Bimap(byte[] b) {
2         if (b.length != 0) {
3             return BitmapFactory.decodeByteArray(b, 0, b.length);
4         } else {
5             return null;
6         }
7     }

4、Bitmap缩放

 1     public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) {
 2         int w = bitmap.getWidth();
 3         int h = bitmap.getHeight();
 4         Matrix matrix = new Matrix();
 5         float scaleWidth = ((float) width / w);
 6         float scaleHeight = ((float) height / h);
 7         matrix.postScale(scaleWidth, scaleHeight);
 8         Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);
 9         return newbmp;
10     }

5、将Drawable转化为Bitmap

 1 public static Bitmap drawableToBitmap(Drawable drawable) {
 2         // 取 drawable 的长宽
 3         int w = drawable.getIntrinsicWidth();
 4         int h = drawable.getIntrinsicHeight();
 5 
 6         // 取 drawable 的颜色格式
 7         Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
 8                 : Bitmap.Config.RGB_565;
 9         // 建立对应 bitmap
10         Bitmap bitmap = Bitmap.createBitmap(w, h, config);
11         // 建立对应 bitmap 的画布
12         Canvas canvas = new Canvas(bitmap);
13         drawable.setBounds(0, 0, w, h);
14         // 把 drawable 内容画到画布中
15         drawable.draw(canvas);
16         return bitmap;
17     }

6、获得圆角图片

 1     public static Bitmap getRoundedCornerBitmap(Bitmap bitmap, float roundPx) {
 2         int w = bitmap.getWidth();
 3         int h = bitmap.getHeight();
 4         Bitmap output = Bitmap.createBitmap(w, h, Config.ARGB_8888);
 5         Canvas canvas = new Canvas(output);
 6         final int color = 0xff424242;
 7         final Paint paint = new Paint();
 8         final Rect rect = new Rect(0, 0, w, h);
 9         final RectF rectF = new RectF(rect);
10         paint.setAntiAlias(true);
11         canvas.drawARGB(0, 0, 0, 0);
12         paint.setColor(color);
13         canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
14         paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
15         canvas.drawBitmap(bitmap, rect, rect, paint);
16 
17         return output;
18     }

7、获得带倒影的图片

 1     public static Bitmap createReflectionImageWithOrigin(Bitmap bitmap) {
 2         final int reflectionGap = 4;
 3         int w = bitmap.getWidth();
 4         int h = bitmap.getHeight();
 5 
 6         Matrix matrix = new Matrix();
 7         matrix.preScale(1, -1);
 8 
 9         Bitmap reflectionImage = Bitmap.createBitmap(bitmap, 0, h / 2, w,
10                 h / 2, matrix, false);
11 
12         Bitmap bitmapWithReflection = Bitmap.createBitmap(w, (h + h / 2),
13                 Config.ARGB_8888);
14 
15         Canvas canvas = new Canvas(bitmapWithReflection);
16         canvas.drawBitmap(bitmap, 0, 0, null);
17         Paint deafalutPaint = new Paint();
18         canvas.drawRect(0, h, w, h + reflectionGap, deafalutPaint);
19 
20         canvas.drawBitmap(reflectionImage, 0, h + reflectionGap, null);
21 
22         Paint paint = new Paint();
23         LinearGradient shader = new LinearGradient(0, bitmap.getHeight(), 0,
24                 bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff,
25                 0x00ffffff, TileMode.CLAMP);
26         paint.setShader(shader);
27         // Set the Transfer mode to be porter duff and destination in
28         paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
29         // Draw a rectangle using the paint with our linear gradient
30         canvas.drawRect(0, h, w, bitmapWithReflection.getHeight()
31                 + reflectionGap, paint);
32 
33         return bitmapWithReflection;
34     }

三、Drawable

1、Bitmap转换成Drawable

1 Bitmap bm=xxx; //xxx根据你的情况获取
2 BitmapDrawable bd= new BitmapDrawable(getResource(), bm); 
3 因为BtimapDrawable是Drawable的子类，最终直接使用bd对象即可。

2、Drawable缩放

 1     public static Drawable zoomDrawable(Drawable drawable, int w, int h) {
 2         int width = drawable.getIntrinsicWidth();
 3         int height = drawable.getIntrinsicHeight();
 4         // drawable转换成bitmap
 5         Bitmap oldbmp = drawableToBitmap(drawable);
 6         // 创建操作图片用的Matrix对象
 7         Matrix matrix = new Matrix();
 8         // 计算缩放比例
 9         float sx = ((float) w / width);
10         float sy = ((float) h / height);
11         // 设置缩放比例
12         matrix.postScale(sx, sy);
13         // 建立新的bitmap，其内容是对原bitmap的缩放后的图
14         Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,
15                 matrix, true);
16         return new BitmapDrawable(newbmp);
17     }