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 }
转载地址：http://dyh7077063.iteye.com/blog/970672