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     }

本文转自的博客