Byte[] Bitmap 转化

	public Bitmap getBitmap(byte[] bytes) {
		Options opt = new Options();
		opt.inJustDecodeBounds = true; //只分配边界不分配像素DecodeBitmap时候
		decodeBitmap(bytes, opt);
		if (opt.outHeight * opt.outWidth < MAX_IMAGE_PIXELS) {
			return decodeBitmap(bytes, null);
			}
		return null;
		}	
	
	public byte[] getBytes(Bitmap bitmap)
	{
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
		return baos.toByteArray();
	}
	public Bitmap resizeImage(byte[] original, int maxWidth, int maxHeight, boolean stretch)
	{
		Options opt = new Options();
		opt.inJustDecodeBounds = true;
		decodeBitmap(original, opt);
		
		int width = opt.outWidth;
		int height = opt.outHeight;
		// Scale the bitmap as we're decoding it to avoid out of memory errors.
		opt.inJustDecodeBounds = false;
		if (width > maxWidth && height > maxHeight) {
			opt.inSampleSize = Math.min(width / maxWidth, height / maxHeight);
		} else if (width > maxWidth) {
			opt.inSampleSize = width / maxWidth;
		} else if (height > maxHeight) {
			opt.inSampleSize = height / maxHeight;
		}
		int powerOfTwo = 1; 
		while (powerOfTwo * 2 < opt.inSampleSize) {
			powerOfTwo *= 2;
		}
		// According to docs, powers of two are more efficient and more accurate.
		opt.inSampleSize = powerOfTwo;
		Bitmap scaled = decodeBitmap(original, opt);
		if (scaled != null) {
			width = scaled.getWidth();
			height = scaled.getHeight();
		float scaleWidth = ((float)maxWidth) / width;
		float scaleHeight = ((float)maxHeight) / height;
		if (!stretch) {
			if ((scaleWidth * height) > maxHeight) {
				scaleWidth = scaleHeight;
			} else {
				scaleHeight = scaleWidth;
			}
		}
		Matrix matrix = new Matrix();
		matrix.postScale(scaleWidth, scaleHeight);
			return Bitmap.createBitmap(scaled, 0, 0, width, height, matrix, true); //缩放图像
	}
		return null;
	}
	
	private Bitmap decodeBitmap(byte[] bytes, Options opt) {
		Bitmap retval = null;
		if (bytes != null) {
			try {
				retval = BitmapFactory.decodeByteArray(bytes, 0, bytes.length, opt);
			} catch (OutOfMemoryError oome) {
				Log.e(ImageHelper.class.getName(), "Out of memory, trying GC...", oome);
				System.gc();
			} catch (Exception e) {
				Log.e(ImageHelper.class.getName(), "Error decoding bitmap",e);
			}
		}	
		return retval;
	}