The method decodeSampledBitmapFromResource
is not memory efficient because it uses 3 streams: the ByteArrayOutputStream baos, ByteArrayInputStream is1 and ByteArrayInputStream is2, each of those stores the same stream data of the image (one byte array for each).
And when I test with my device (LG nexus 4) to decode an 2560x1600 image on SDcard to target size 800 it takes something like this:
03-13 15:47:52.557: E/DecodeBitmap(11177): dalvikPss (beginning) = 1780
03-13 15:47:53.157: E/DecodeBitmap(11177): dalvikPss (decoding) = 26393
03-13 15:47:53.548: E/DecodeBitmap(11177): dalvikPss (after all) = 30401 time = 999
We can see: too much memory allocated (28.5 MB) just to decode 4096000 a pixel image.
Solution: we read the InputStream and store the data directly into one byte array and use this byte array for the rest work.
Sample code:
public Bitmap decodeSampledBitmapFromResourceMemOpt(
InputStream inputStream, int reqWidth, int reqHeight) {
byte[] byteArr = new byte[0];
byte[] buffer = new byte[1024];
int len;
int count = 0;
try {
while ((len = inputStream.read(buffer)) > -1) {
if (len != 0) {
if (count + len > byteArr.length) {
byte[] newbuf = new byte[(count + len) * 2];
System.arraycopy(byteArr, 0, newbuf, 0, count);
byteArr = newbuf;
}
System.arraycopy(buffer, 0, byteArr, count, len);
count += len;
}
}
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeByteArray(byteArr, 0, count, options);
options.inSampleSize = calculateInSampleSize(options, reqWidth,
reqHeight);
options.inPurgeable = true;
options.inInputShareable = true;
options.inJustDecodeBounds = false;
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
int[] pids = { android.os.Process.myPid() };
MemoryInfo myMemInfo = mAM.getProcessMemoryInfo(pids)[0];
Log.e(TAG, "dalvikPss (decoding) = " + myMemInfo.dalvikPss);
return BitmapFactory.decodeByteArray(byteArr, 0, count, options);
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
The method that does the calculation:
public void onButtonClicked(View v) {
int[] pids = { android.os.Process.myPid() };
MemoryInfo myMemInfo = mAM.getProcessMemoryInfo(pids)[0];
Log.e(TAG, "dalvikPss (beginning) = " + myMemInfo.dalvikPss);
long startTime = System.currentTimeMillis();
FileInputStream inputStream;
String filePath = Environment.getExternalStorageDirectory()
.getAbsolutePath() + "/test2.png";
File file = new File(filePath);
try {
inputStream = new FileInputStream(file);
// mBitmap = decodeSampledBitmapFromResource(inputStream, 800, 800);
mBitmap = decodeSampledBitmapFromResourceMemOpt(inputStream, 800,
800);
ImageView imageView = (ImageView) findViewById(R.id.image);
imageView.setImageBitmap(mBitmap);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
myMemInfo = mAM.getProcessMemoryInfo(pids)[0];
Log.e(TAG, "dalvikPss (after all) = " + myMemInfo.dalvikPss
+ " time = " + (System.currentTimeMillis() - startTime));
}
And the result:
03-13 16:02:20.373: E/DecodeBitmap(13663): dalvikPss (beginning) = 1823
03-13 16:02:20.923: E/DecodeBitmap(13663): dalvikPss (decoding) = 18414
03-13 16:02:21.294: E/DecodeBitmap(13663): dalvikPss (after all) = 18414 time = 917