android 利用canvas 獲取裁切或者合併後的bitmap對象

1  圖片裁切

    備註：創建圖片還是很耗內存的，所以不論是圖片的合併還是裁切都比較耗內存，利用canvas還是可以以節       約內存的方式實現

       mBitWidth 爲原圖寬度，mBitheight爲原圖高度

       mSrcbmp = bitmap;  //原圖bitmap對象
       mBitWidth = mSrcbmp.getWidth();
       mBitheight = mSrcbmp.getHeight();

//圖片裁切canvas方式（下面是一張圖片裁切爲4張小圖均可返回bitmap對象）
private Bitmap cutBitmap() {
	Bitmap bitmap = Bitmap.createBitmap(mBitWidth / 2, mBitheight / 2, Config.RGB_565);
	Canvas canvas = new Canvas(bitmap);
	Rect src1 = new Rect(0, 0, mBitWidth / 2, mBitheight / 2);   
	Rect sr2 = new Rect(mBitWidth / 2, 0, mBitWidth, mBitheight / 2);   
	Rect src3 = new Rect(0, mBitheight / 2, mBitWidth / 2, mBitheight); 
	Rect src4 = new Rect(mBitWidth / 2, mBitheight / 2, mBitWidth, mBitheight); 
	Rect dsc = new Rect(0, 0, mBitWidth / 2, mBitheight / 2);   
	canvas.drawBitmap(mSrcbmp, src4, dsc, mPaint);  
	return bitmap;
}

接着在ondraw下面繪製

Rect rect1 = new Rect(0, 0, mBitWidth / 2, mBitheight / 2); 
canvas.drawBitmap(cutBitmap(), null, rect1, mPaint);

圖片合併canvas方式，直接在ondraw（）函數下繪製，但只起到顯示作用，如何得到合併後的bitmap對象呢，如下例：

Rect rect1 = new Rect(0, 0, mBitWidth, mBitheight); 
Rect rect2 = new Rect(mBitWidth, 0, mBitWidth * 2, mBitheight);  
canvas.drawBitmap(mSrcbmp, null, rect1, mPaint);//在 0，0座標開始畫入src  
canvas.drawBitmap(mSrcbmp, null, rect2, mPaint);

canvas方式獲取合併後的bitmap對象

private Bitmap mergeBitmap() {
	Rect rect1 = new Rect(0, 0, mBitWidth, mBitheight); 
	Rect rect2 = new Rect(mBitWidth, 0, mBitWidth * 2, mBitheight);   
	Bitmap bitmap = Bitmap.createBitmap(mBitWidth * 2, mBitheight, Config.RGB_565);
	Canvas canvas = new Canvas(bitmap);
	canvas.drawBitmap(mSrcbmp, null, rect1, mPaint);
	canvas.drawBitmap(mSrcbmp, null, rect2, mPaint);
	return bitmap;
}

接着在ondraw()函數下繪製

Rect rect1 = new Rect(0, 0, mBitWidth * 2, mBitheight); 
canvas.drawBitmap(mergeBitmap(), null, rect1, mPaint);