Develop Reference

Byte Array to 2D array

What My code does . is take a snapshot of the map convert it to gray (opencv) and then make it to byte array.
Now what I dont know how to start doing is making this Bytearray to a 2D Array,
here is a block of the code.
Date now = new Date();
android.text.format.DateFormat.format("yyyy-MM-dd_hh:mm:ss",now);
try {
StrictMode.ThreadPolicy old = StrictMode.getThreadPolicy();
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder(old)
.permitDiskWrites()
.build());
String mPath = Environment.getExternalStorageDirectory().toString() + "/" + now + ".jpg";
File imageFile = new File(mPath);
FileOutputStream out = new FileOutputStream(imageFile);
bitmap.compress(Bitmap.CompressFormat.PNG,90,out);
Log.d("Image:","Saved Snashot. Starting covertion");
//show snapshot in imageview
ImageView imgview = (ImageView) findViewById(R.id.imageView);
Bitmap smyBitmap = BitmapFactory.decodeFile(mPath);
Bitmap myBitmap = BitmapFactory.decodeFile(mPath);
imgview.setImageBitmap(smyBitmap);
Mat mat = new Mat(myBitmap.getHeight(),myBitmap.getWidth(),CvType.CV_8UC3);
Mat mat1 = new Mat(myBitmap.getHeight(),myBitmap.getWidth(),CvType.CV_8UC1);
Imgproc.cvtColor(mat,mat1,Imgproc.COLOR_BGR2GRAY);
ImageView imgview2 = (ImageView) findViewById(R.id.imageView2);
Mat tmp = new Mat (myBitmap.getWidth(), myBitmap.getHeight(), CvType.CV_8UC1);
Utils.bitmapToMat(myBitmap, tmp);
Imgproc.cvtColor(tmp, tmp, Imgproc.COLOR_RGB2GRAY);
Utils.matToBitmap(tmp, myBitmap);
// Utils.matToBitmap(mat1,img);
String mPathgray = Environment.getExternalStorageDirectory().toString() + "/" + now + "gray.jpg";
File imageFilegray = new File(mPathgray);
FileOutputStream gout = new FileOutputStream(imageFilegray);
bitmap.compress(Bitmap.CompressFormat.PNG,90,gout);
byte[] byteArray = bttobyte(myBitmap);
Log.d("location"," " + mPathgray);
imgview2.setImageBitmap(myBitmap);
Log.d("Activity", "Byte array: "+ Arrays.toString(byteArray));
}
catch (Exception e) {
e.printStackTrace();
}
}
};
mMap.snapshot(callback);
Log.d("test","test2");
}
});
}
public byte[] bttobyte(Bitmap bitmap) {
ByteArrayOutputStream stream = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.JPEG, 70, stream);
return stream.toByteArray();
}

The problem you are trying to solve is actually extracting image data from JPEG encoding in the byte array. It is not as simple as being stored pixel by pixel in a grid of width and height equal to your image size, as you seem to be implying. That is a consequence of using this
bitmap.compress(Bitmap.CompressFormat.JPEG, 70, stream);
For example that byte data actually might encode JFIF format:
0xffd8 - SOI - exactly 1 - start of image
e.g. 0xffe0 - zero or more - e.g. APP0 for JFIF - [some sort of header, either JFIF or EXIF].
0xffdb - DQT - one or more - define quantisation tables. These are the main source of quality in the image.
0xffcn - SOFn - exactly one - start of frame. SOF0 indicates a baseline DCT JPEG
0xffc4 - DHT - one or more - define Huffman tables. These are used in the final lossless encoding steps.
0xffda - SOS - exactly one (for baseline, more than one intermixed with more DHTs if progressive) - start of stream. This is where the actual data starts.
0xffd9 - EOI - exactly one - end of image.
Essentially once you have transformed your bitmap, you need a JPEG decoder to parse this data.
I think what you want is to be working with the original bitmap. For example there are APIs to extract pixel data. That is what you need if I understand what it is you want to do correctly.
Bitmap.getPixels(int[] pixels,
int offset,
int stride,
int x,
int y,
int width,
int height)
The array pixels[] is filled with data. You can then parse the array if you want to store it in a w by h 2D array by iterating copying the data. Something like:
int offset = 0;
int pixels2d[w][h]= new int[w][h];
for (int[] row : pixels2d) {
System.arraycopy(pixels, offset, row, 0, row.length);
offset += row.length;
}

You just create a new array with 2 dimensions
byte[][] picture = new byte[myBitmap.getWidth()][,myBitmap.getHeight()]
which you can access via
byte myByte = picture[x][y]
after this you iterate your original bytarray by line followed by row

Imebra - Change color contrasts

I am able to load dicom image using imebra, and want to change the colors of image, but cant figure out a way. I want to achieve functionality as in Dicomite app.
Following is my code:
public void loadDCM() {
com.imebra.DataSet loadedDataSet = com.imebra.CodecFactory.load(dicomPath.getPath());
com.imebra.VOIs voi = loadedDataSet.getVOIs();
com.imebra.Image image = loadedDataSet.getImageApplyModalityTransform(0);
// com.imebra.Image image = loadedDataSet.getImage(0);
String colorSpace = image.getColorSpace();
long width = image.getWidth();
long height = image.getHeight();
TransformsChain transformsChain = new TransformsChain();
com.imebra.DrawBitmap drawBitmap = new com.imebra.DrawBitmap(transformsChain);
com.imebra.TransformsChain chain = new com.imebra.TransformsChain();
if (com.imebra.ColorTransformsFactory.isMonochrome(image.getColorSpace())) {
// Allocate a VOILUT transform. If the DataSet does not contain any pre-defined
// settings then we will find the optimal ones.
VOILUT voilutTransform = new VOILUT();
// Retrieve the VOIs (center/width pairs)
com.imebra.VOIs vois = loadedDataSet.getVOIs();
// Retrieve the LUTs
List < LUT > luts = new ArrayList < LUT > ();
for (long scanLUTs = 0;; scanLUTs++) {
try {
luts.add(loadedDataSet.getLUT(new com.imebra.TagId(0x0028, 0x3010), scanLUTs));
} catch (Exception e) {
break;
}
}
if (!vois.isEmpty()) {
voilutTransform.setCenterWidth(vois.get(0).getCenter(), vois.get(0).getWidth());
} else if (!luts.isEmpty()) {
voilutTransform.setLUT(luts.get(0));
} else {
voilutTransform.applyOptimalVOI(image, 0, 0, width, height);
}
chain.addTransform(voilutTransform);
com.imebra.DrawBitmap draw = new com.imebra.DrawBitmap(chain);
// Ask for the size of the buffer (in bytes)
long requestedBufferSize = draw.getBitmap(image, drawBitmapType_t.drawBitmapRGBA, 4, new byte[0]);
byte buffer[] = new byte[(int) requestedBufferSize]; // Ideally you want to reuse this in subsequent calls to getBitmap()
ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
// Now fill the buffer with the image data and create a bitmap from it
drawBitmap.getBitmap(image, drawBitmapType_t.drawBitmapRGBA, 4, buffer);
Bitmap renderBitmap = Bitmap.createBitmap((int) image.getWidth(), (int) image.getHeight(), Bitmap.Config.ARGB_8888);
renderBitmap.copyPixelsFromBuffer(byteBuffer);
image_view.setImageBitmap(renderBitmap);
}

If you are dealing with a monochrome image and you want to modify the presentation luminosity/contrast, then you have to modify the parameters of the VOILUT transform (voilutTransform variable in your code).
You can get the center and width that the transform is applying to the image before calculating the bitmap to be displayed, then modify them before calling drawBitmap.getBitmap again.
E.g., to double the contrast:
voilutTransform.setCenterWidth(voilutTransform.getCenter(), voilutTransform.getWidth() / 2);
// Now fill the buffer with the image data and create a bitmap from it
drawBitmap.getBitmap(image, drawBitmapType_t.drawBitmapRGBA, 4, buffer);
See this answer for more details about the center/width

Android Nexus 10 blank png from JNI ByteArray

I am developing an application using JNI and a third party engine (Unreal Engine 4) in charge of managing the graphics pipeline/rendering.
The third party engine is written in C++, thus the need of using JNI to bridge it with Android.
The app requires to save a screenshot on the device of what is being displayed on the screen (in other words a dump of the framebuffer).
The third party engine exposes an API that calls a custom handler, passing in the width, height and color data of the screen.
colordata is a custom container of uint8 representing RGBA components.
I successfully managed to convert the colorData to a jbyteArray and pass it as an argument to a function on the JAVA side.
On the java side things are simpler: I create a bitmap from the byteArray, flip it and save it as a jpg/png via a custom AsyncTask.
The problem:
The code works marvellously o Samsung Galaxy S4/Note3 (Both Android 5.0), whereas on a Nexus 10 Android version 5.1.1 the png that gets saved is blank.
I am afraid that the problem with this lies on a depper level than the ones I have access to, i.e. graphics card/drivers/OS version, but I am not an expert in that field, so I would like to know if someone has already experienced a similar issue or could shed some light on what is causing it.
This is the code used to bridge the engine with Java (I started c++ with this project so maybe there are ownership/memory issues in this snippet. You are more than welcome to correct me in case :))
void AndroidInterface::SaveBitmap(const TArray<FColor>& colorData, int32 width, int32 height) {
JNIEnv* env = FAndroidApplication::GetJavaEnv(true);
TArray<FColor> bitmap = colorData;
TArray<uint8> compressedBitmap;
FImageUtils::CompressImageArray(width, height, bitmap, compressedBitmap);
size_t len = width*height*compressedBitmap.GetTypeSize();
LOGD("===========Width: %i, height: %i - Len of bitmap element: %i==========", width, height, len);
jbyteArray bitmapData = env->NewByteArray(len);
LOGD("===========Called new byte array==========");
env->SetByteArrayRegion(bitmapData, 0, len, (const jbyte*)compressedBitmap.GetData() );
LOGD("===========Populated byte array==========");
check (bitmapData != NULL && "Couldn't create byte array");
jclass gameActivityClass = FAndroidApplication::FindJavaClass("com/epicgames/ue4/GameActivity");
check (gameActivityClass != nullptr && "GameActivityClassNotFound");
//get the method signature to take a game screenshot
jmethodID saveScreenshot = env->GetMethodID(gameActivityClass, "saveScreenshot", "([BII)V");
env->CallVoidMethod(AndroidInterface::sGameActivity, saveScreenshot, bitmapData, width, height);
env->DeleteLocalRef(bitmapData);
}
This is the java code in charge of converting from byte[] to Bitmap:
public void saveScreenshot(final byte[] colors, int width, int height) {
android.util.Log.d("GameActivity", "======saveScreenshot called. Width: " + width + " height: " + height + "=======");
android.util.Log.d("GameActivity", "Color content---->\n " + Arrays.toString(colors));
final BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inPreferredConfig = Bitmap.Config.ARGB_8888;
final Bitmap bitmap = BitmapFactory.decodeByteArray(colors, 0, colors.length, opts);
final FlipBitmap flipBitmapTask = new FlipBitmap();
flipBitmapTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, bitmap);
}
FlipBitmap is the AsyncTask in charge of saving the bitmap to a file:
private class FlipBitmap extends AsyncTask<Bitmap, Void, File> {
#Override
protected File doInBackground(Bitmap... params) {
final Bitmap src = params[0];
final File file = new File(MainActivity.SCREENSHOT_FOLDER + "screenshot" + System.currentTimeMillis() + ".png");
final Matrix matrix = new Matrix();
matrix.setScale(1, -1);
final Bitmap dst = Bitmap.createBitmap(src, 0, 0, src.getWidth(), src.getHeight(), matrix, false);
try {
final FileOutputStream out = new FileOutputStream(file);
dst.compress(Bitmap.CompressFormat.PNG, 90, out);
out.flush();
out.close();
} catch (Exception e) {
e.printStackTrace();
}
return file;
}
#Override
protected void onPostExecute(File file) {
android.util.Log.d("GameActivity", "FlipBitmap onPostExecute");
if (file.exists()) {
final Intent i = new Intent(Intent.ACTION_SENDTO);
i.setData(Uri.parse("mailto:" + Globals.Network.MAIL_TO));
i.putExtra(Intent.EXTRA_SUBJECT, Globals.Network.MAIL_SUBJECT);
i.putExtra(Intent.EXTRA_TEXT, mBodyEmail);
i.putExtra(Intent.EXTRA_STREAM, Uri.parse("file://" + file.getAbsolutePath()));
startActivity(Intent.createChooser(i, "Invia via email"));
}
}
}
Thanks in advance!

Restoring the image from Native Memory using NDK returns Black Image with No display

I am trying to restore the image from Native memory (using NDK,C/C++) but that returns me an Black Image.
What i am doing ::
1)get the image from Drawable
2)apply the rotation to the image
3)After rotation apply the grayscale effect to the image
4)At the end i am trying to save the grayscale image in SD Card
For all the above steps, i am referring this awesome lib,which have the native method to store and restore the images.
Please note image is being stored in the SD card but when i am trying to see the image,its totally black with no display at all.
My Java Implementation ::
public boolean onOptionsItemSelected(MenuItem item)
{
switch (item.getItemId())
{
case R.id.item_rotate_90:
options.inPreferredConfig = Config.ARGB_8888;
bitmapOrig = BitmapFactory.decodeResource(this.getResources(), R.drawable.sample_cam,options);
storeBitmap(bitmapOrig);
bitmapOrig.recycle();
rotateBitmap(90,_handler);
tempBmp=getBitmapAndFree();
bitmapWip = Bitmap.createBitmap(bitmapOrig.getWidth(),bitmapOrig.getHeight(),Config.ALPHA_8);
jniConvertToGray(tempBmp,bitmapWip);
if(bitmapWip!=null)
{
try
{
Bitmap b = Bitmap.createBitmap(bitmapWip.getWidth(),bitmapWip.getHeight(),Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(b);
Paint paint = new Paint();
ColorMatrix cm = new ColorMatrix();
ColorMatrixColorFilter f = new ColorMatrixColorFilter(cm);
paint.setColorFilter(f);
c.drawBitmap(bitmapWip, 0, 0, paint);
storeBitmap(b);
SaveGrayScaledImage(b);
b.recycle();
tempBmp.recycle();
} catch (IOException e) {
e.printStackTrace();
}
ivDisplay.setImageBitmap(bitmapWip);
}
break;
}
}
I have not make any changes in native method(means using the same method as this lib have for storing and restoring the image).
Saving image to SD Card ::
private void SaveGrayScaledImage(Bitmap finalBitmap)throws IOException
{
String imageFileName = "Temp" + "_gray";
File albumF = new File("/mnt/sdcard/","gray_img");
if(!albumF.exists())
{
albumF.mkdirs();
}
// File imageF = File.createTempFile(imageFileName, JPEG_FILE_SUFFIX,
// albumF);
File imageF = new File(albumF,imageFileName + ".jpeg");
if (imageF.exists()) {
imageF.delete();
imageF.createNewFile();
}
try {
FileOutputStream out = new FileOutputStream(imageF);
finalBitmap.compress(Bitmap.CompressFormat.JPEG, 100, out);
out.flush();
out.close();
} catch (Exception e) {
e.printStackTrace();
imageF = null;
}
}
While googling, i found that(may be i am wrong) image which returns for Native Memory have the ALPHA_8 bitmap config,so i convert the config ALPHA_8 t0 ARGB_8888,but the result is same.
Conversion of bitmap from ALPHA_8 to ARGB_8888 ::
Bitmap b = Bitmap.createBitmap(bitmapWip.getWidth(),bitmapWip.getHeight(),Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(b);
Paint paint = new Paint();
ColorMatrix cm = new ColorMatrix();
ColorMatrixColorFilter f = new ColorMatrixColorFilter(cm);
paint.setColorFilter(f);
c.drawBitmap(bitmapWip, 0, 0, paint);
StoreBimap funcation ::
public void storeBitmap(final Bitmap bitmap)
{
if(_handler!=null)
freeBitmap();
_handler=jniStoreBitmapData(bitmap);
}
I have no clue about where i was wrong. i have checked the lib methods and implmentation again and again to find the issue.
I have spent my many hours on this small issue and it really frustrating me.
Let me know please if you need anything else from my side.
Please help me to resolve this issue.
Many Thanks in Advance....
EDIT ::
bitmapHolder=new JniBitmapHolder();
final Options options=new Options();
BitmapFactory.decodeFile(picPath, options);
options.inJustDecodeBounds=true;
options.inPreferredConfig=Config.ARGB_8888;
prepareForDownsampling(options,192,256);
System.gc();
bmpGrayscale=BitmapFactory.decodeFile(picPath,options);
int width = bmpGrayscale.getWidth();
int height = bmpGrayscale.getHeight();
bitmapHolder.storeBitmap(bmpGrayscale);
bmpGrayscale.recycle();
Bitmap thumbnail = null;
int rotationInDegrees = 0;
if (picPath != null) {
Uri uri = Uri.parse(picPath);
ExifInterface exif = null;
try {
exif = new ExifInterface(uri.getPath());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
int rotation = exif.getAttributeInt(
ExifInterface.TAG_ORIENTATION,
ExifInterface.ORIENTATION_NORMAL);
rotationInDegrees = exifToDegrees(rotation);
}
rotationInDegrees = 90;
ByteBuffer _handler =null;
switch(rotationInDegrees)
{
case 90:
bitmapHolder.rotateBitmapCw90();
break;
case 180:
bitmapHolder.rotateBitmap180();
break;
}
Bitmap bitmapWip = Bitmap.createBitmap(width,height,Config.ALPHA_8);
bitmapHolder.bitmapGrayScale(bitmapWip);
if(bitmapWip!=null){
File CurrentFile = saveGrayScaledIamge(bitmapWip,
takePhotoFile);
}
I have followed your suggestion/steps but the result is same,getting black image with no display.

ok I've found multiple problems and tips for improvements:
the first createBitmap is run with width*height on a bitmap that got rotated instead of height*width. this should be as:
rotateBitmap(90,_handler);
tempBmp=getBitmapAndFree();
bitmapWip=Bitmap.createBitmap(bitmapOrig.getHeight(),bitmapOrig.getWidth(),Config.ALPHA_8);
when saving file you don't get the correct path (you use a hardcoded path, and Lint warns about it).
jniConvertToGray doesn't really need to go over arrays and can just use a pointer, as it just runs on a single pixel. you store the bitmap into JNI twice instead of once (just do: store, rotate, grayscale, restore&free).
you don't use the new bitmap after you have finished working on it, so if I call rotation multiple times, it doesn't seem to do anything.
you already have bitmapWip rotated and grayscaled. why do you need to make a new bitmap that has its content in it, do a grayscale on it, and then save it ?
functions should be named with lowercase letter in the beginning of their names.
and finally , the most important thing: you use ALPHA_8 for the image that you show and need to save to file. this configuration has no color. it's a mask. In order to see the problem, you should set a background color to the imageView :
ivDisplay.setBackgroundColor(0xFFff0000);
before choosing the rotation, you see nothing red. after choosing it, everything you think is white, has actually become red. that's because it's transparent...
If in any phase of your development you've succeeded saving the image to a file and thought it's a black image (yet the size is not 0) , try to edit it and put a background behind it. Maybe you got lucky and just got transparent pixels...
Adding the fact that you save the file to a jpg format, which doesn't support transparency, might also contribute to unexpected behaviors.
in order to solve this, you should use the same technique i've used - use a single bitmap all the time. no need to create so many. only one should exist on the java world, and it should support having colors.

Decoded bitmap results in larger size

I am trying to store a bitmap (that i have previously read from a file) after decoding it in a preferable size using BitmapFactory.Options.inSampleSize. The problem is that the file size of the stored bitmap is at least double the size of the original file. I have searched a lot and could not find how i can deal with this, since i don't want it to happen for memmory efficiency (later i reuse the stored bitmap). Here is my method that does what i describe:
private Bitmap decodeFileToPreferredSize(File f) {
Bitmap b = null;
try {
// Decode image size
Log.i("Bitmap", "Imported image size: " + f.length() + " bytes");
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeFile(f.getAbsolutePath(), o);
//Check if the user has defined custom image size
int scale = 1;
if(pref_height != -1 && pref_width != -1) {
if (o.outHeight > pref_height || o.outWidth > pref_width) {
scale = (int) Math.pow(
2,
(int) Math.round(Math.log(pref_width
/ (double) Math.max(o.outHeight, o.outWidth))
/ Math.log(0.5)));
}
}
// Decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
b = BitmapFactory.decodeFile(f.getAbsolutePath(), o2);
String name = "Image_" + System.currentTimeMillis() + ".jpg";
File file = new File(Environment.getExternalStorageDirectory(), name);
FileOutputStream out = new FileOutputStream(file);
b.compress(Bitmap.CompressFormat.JPEG, 100, out);
out.close();
Log.i("Bitmap", "Exported image size: " + file.length() + " bytes");
} catch (Exception e) {
b = null;
}
return b;
}
UPDATE I saw the densities on the two image files. The one that came from camera intent has 72 dpi density for width and height. The image file created from my above method has 96 dpi density for width and height. This explains why a 0.5 MByte image that came form the camera is resized in approximatelly 2.5 MByte with my above method since the rescale factor is (96/72) * 2 ~= 2.5. For some reason, the bitmap i create does not take the density of the image that came from the camera. I tried to set the density with all variation of BitmapFactory.Options.inDensity but no luck. Also i tried to change the bitmap density with bitmap.setDensity(int dpi); but still no effect. So, my new question is if there is a way to define the density of the bitmap when the image is stored.
Thanks in advance.

I had a similar issue. When I downloaded images from web they used more space on the SD than they did when downloaded to my PC from browser. I think the issue is simply that BitmapFactory saves the images in a non optimzed format of some sort.
My workaround was to use following instead of the bitmapfactory:
try {
try {
is = yourinputstream;
// Consider reading stream twice and return the bitmap.
os = youroutputstream;
byte data[] = new byte[4096];
int count;
while ((count = is.read(data)) != -1) {
os.write(data, 0, count);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if(is != null) {
is.close();
}
if(os != null) {
os.close();
}
}
} catch (IOException e) {
e.printStackTrace();
}

You are correct that the problem is in a density change.
This thread revealed a solution: BitmapFactory returns bigger image than source
Before decoding also disable inScaled:
options.inSampleSize = 2; //or however you desire, power of 2
options.inScaled = false;
This will keep the density from changing and you will see the decrease in size you were looking for.

When BitmapFactory.Options.inSampleSize = 0.5, it does 100% / 0.5 = 200%.
What you want I think is BitmapFactory.Options.inSampleSize = 2, it does 100% / 2 = 50%