一、相關概念
1、Drawable就是一個可畫的對象，其可能是一張位圖（BitmapDrawable），也可能是一個圖形（ShapeDrawable），還有可能是一個圖層（LayerDrawable），我們根據畫圖的需求，創建相應的可畫對象
2、Canvas畫布，繪圖的目的區域，用於繪圖
3、Bitmap位圖，用於圖的處理
4、Matrix矩陣
二、Bitmap
1、從資源中獲取Bitmap
Java代碼 
1. Resources res = getResources();
2. Bitmap bmp = BitmapFactory.decodeResource(res, R.drawable.icon);
2、Bitmap → byte[]
Java代碼
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
Java代碼
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縮放
Java代碼
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、將Drawable轉化爲Bitmap
Java代碼
1. public static Bitmap drawableToBitmap(Drawable drawable) {
2. // 取 drawable 的長寬
3. int w = drawable.getIntrinsicWidth();
4. int h = drawable.getIntrinsicHeight();
5.
6. // 取 drawable 的顏色格式
7. Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
8. : Bitmap.Config.RGB_565;
9. // 建立對應 bitmap
10. Bitmap bitmap = Bitmap.createBitmap(w, h, config);
11. // 建立對應 bitmap 的畫布
12. Canvas canvas = new Canvas(bitmap);
13. drawable.setBounds(0, 0, w, h);
14. // 把 drawable 內容畫到畫布中
15. drawable.draw(canvas);
16. return bitmap;
17. }
6、獲得圓角圖片
Java代碼
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、獲得帶倒影的圖片
Java代碼
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轉換成Drawable
Java代碼
1. Bitmap bm=xxx; //xxx根據你的情況獲取
2. BitmapDrawable bd= new BitmapDrawable(getResource(), bm);
3. 因爲BtimapDrawable是Drawable的子類，最終直接使用bd對象即可。
2、Drawable縮放
Java代碼
1. public static Drawable zoomDrawable(Drawable drawable, int w, int h) {
2. int width = drawable.getIntrinsicWidth();
3. int height = drawable.getIntrinsicHeight();
4. // drawable轉換成bitmap
5. Bitmap oldbmp = drawableToBitmap(drawable);
6. // 創建操作圖片用的Matrix對象
7. Matrix matrix = new Matrix();
8. // 計算縮放比例
9. float sx = ((float) w / width);
10. float sy = ((float) h / height);
11. // 設置縮放比例
12. matrix.postScale(sx, sy);
13. // 建立新的bitmap，其內容是對原bitmap的縮放後的圖
14. Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,
15. matrix, true);
16. return new BitmapDrawable(newbmp);
17. }