Android繪制進階之四:在位圖上繪制文本並旋轉

1,點擊按鈕,指定action和uri,設定結果碼(ResultCode).到達手機默認相冊的Gallery.

 
 
 

 

代碼如下:
 
1. public void onClick(View v) {
2.         // TODO Auto-generated method stub
3.         Intent intent = new Intent(Intent.ACTION_PICK,
4.                 android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);// 啟動照片Gallery
5.         startActivityForResult(intent, 0);
6.     }
2,選擇圖片,返回所選照片uri信息
代碼如下:
 
1. @Override
2.     protected void onActivityResult(int requestCode, int resultCode,
3.             Intent intent) {
4.         // TODO Auto-generated method stub
5.         super.onActivityResult(requestCode, resultCode, intent);
6. 
7.         if (resultCode == RESULT_OK) {// 操作成功 www.aiwalls.com
8.             Uri imgFileUri = intent.getData();// 獲得所選照片的信息
3,處理圖片,設定合適的尺寸(正好適應屏幕)
設定BitmapFactory.Options 參數inJustDecodeBounds = true,即不創建bitmap,但可獲取bitmap的相關屬性。以寬高比例差距 最大者為基準。
代碼如下:
 
1. // 由於返回的圖像可能太大而無法完全加載到內存中。系統有限制,需要處理。
2.             Display currentDisplay = getWindowManager().getDefaultDisplay();
3.             int defaultHeight = currentDisplay.getHeight();
4.             int defaultWidth = currentDisplay.getWidth();
5. 
6.             BitmapFactory.Options bitmapFactoryOptions = new BitmapFactory.Options();
7.             bitmapFactoryOptions.inJustDecodeBounds = true;// /隻是為獲取原始圖片的尺寸,而不返回Bitmap對象
8.             // 註上:If set to true, the decoder will return null (no bitmap), but
9.             // the out… fields will still be set,
10.             // allowing the caller to query the bitmap without having to
11.             // allocate the memory for its pixels
12.             try {
13.                 Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver()
14.                         .openInputStream(imgFileUri), null,
15.                         bitmapFactoryOptions);
16.                 int outHeight = bitmapFactoryOptions.outHeight;
17.                 int outWidth = bitmapFactoryOptions.outWidth;
18.                 int heightRatio = (int) Math.ceil((float) outHeight
19.                         / defaultHeight);
20.                 int widthRatio = (int) Math.ceil((float) outWidth
21.                         / defaultWidth);
22. 
23.                 if (heightRatio > 1 || widthRatio > 1) {
24.                     if (heightRatio > widthRatio) {
25.                         bitmapFactoryOptions.inSampleSize = heightRatio;
26.                     } else {
27.                         bitmapFactoryOptions.inSampleSize = widthRatio;
28.                     }
29.                 }
4,inJustDecodeBounds = false,創建將此bitmap賦給第一個ImageView。
代碼如下:
 
1. bitmapFactoryOptions.inJustDecodeBounds = false;
2.                 bitmap = BitmapFactory.decodeStream(getContentResolver()
3.                         .openInputStream(imgFileUri), null,
4.                         bitmapFactoryOptions);
5. 
6.                 mImageShow.setImageBitmap(bitmap);
5,繪制bitmap(選中的圖片),賦給第二個ImageView
a, 繪制正面Bitmap
b,在此Bitmap上繪制文本
c,創建Matrix對象,指定旋轉角度。
d,創建新的bitmap對象,即canvas即將要繪制的傾斜區域
e,繪制
代碼如下:
 
1. // /*
2.                 // * 在位圖上繪制位圖
3.                 // */
4.                 //
5.                 
6.                 Bitmap bitmapAltered = Bitmap.createBitmap(bitmap.getWidth(),
7.                         bitmap.getHeight(), bitmap.getConfig());
8. 
9.                 Canvas canvas = new Canvas(bitmapAltered);// bitmap提供瞭畫佈,隻在此提供瞭大小尺寸,偏移後並未有背景顯示出來
10.                 
11.                 Paint paint = new Paint();
12.                 
13.                 canvas.drawBitmap(bitmap, 0, 0, paint);
14.                 
15.                 paint.setColor(Color.RED);
16. 
17.                 canvas.drawText("hello", 10, 10, paint);
18.                 
19.                 //先繪制正面圖片,再旋轉
20.                 Matrix matrix = new Matrix();
21.                 
22.                 matrix.setRotate(45, 0, 0);     
23.                 //創建一個傾斜的繪制區域
24.                 Bitmap bitmapRotated = Bitmap.createBitmap(bitmapAltered, 0, 0, bitmapAltered.getWidth(), bitmapAltered.getHeight(), matrix, false);
25.                 canvas.drawBitmap(bitmapAltered, matrix, paint);
26.                 mImageAltered.setImageBitmap(bitmapRotated);
 

 

摘自 小新專欄

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