If your app uses custom TensorFlow Lite models, you can use Firebase ML to deploy your models. By deploying models with Firebase, you can reduce the initial download size of your app and update your app's ML models without releasing a new version of your app. And, with Remote Config and A/B Testing , you can dynamically serve different models to different sets of users.
TensorFlow Lite models
TensorFlow Lite models are ML models that are optimized to run on mobile devices. To get a TensorFlow Lite model:
- Use a pre-built model, such as one of the official TensorFlow Lite models .
- Convert a TensorFlow model, Keras model, or concrete function to TensorFlow Lite.
Before you begin
- If you haven't already, add Firebase to your Android project .
- In your module (app-level) Gradle file
(usually
<project>/<app-module>/build.gradle.ktsor<project>/<app-module>/build.gradle), add the dependency for the Firebase ML model downloader library for Android. We recommend using the Firebase Android BoM to control library versioning.Also, as part of setting up Firebase ML model downloader, you need to add the TensorFlow Lite SDK to your app.
dependencies { // Import the BoM for the Firebase platform implementation ( platform ( "com.google.firebase:firebase-bom:34.2.0" )) // Add the dependency for the Firebase ML model downloader library // When using the BoM , you don 't specify versions in Firebase library dependencies implementation ( "com.google.firebase:firebase-ml-modeldownloader" )
// Also add the dependency for the TensorFlow Lite library and specify its version implementation ( "org.tensorflow:tensorflow-lite:2.3.0" ) }By using the Firebase Android BoM , your app will always use compatible versions of Firebase Android libraries.
(Alternative) Add Firebase library dependencies without using the BoM
If you choose not to use the Firebase BoM , you must specify each Firebase library version in its dependency line.
Note that if you use multiple Firebase libraries in your app, we strongly recommend using the BoM to manage library versions, which ensures that all versions are compatible.
dependencies { // Add the dependency for the Firebase ML model downloader library // When NOT using the BoM , you must specify versions in Firebase library dependencies implementation ( "com.google.firebase:firebase-ml-modeldownloader:26.0.0" )
// Also add the dependency for the TensorFlow Lite library and specify its version implementation ( "org.tensorflow:tensorflow-lite:2.3.0" ) } - In your app's manifest, declare that INTERNET permission is required:
<uses-permission android:name="android.permission.INTERNET" />
1. Deploy your model
Deploy your custom TensorFlow models using either the Firebase console or the Firebase Admin Python and Node.js SDKs. See Deploy and manage custom models .
After you add a custom model to your Firebase project, you can reference the
model in your apps using the name you specified. At any time, you can deploy
a new TensorFlow Lite model and download the new model onto users' devices by
calling getModel()
(see below).
2. Download the model to the device and initialize a TensorFlow Lite interpreter
To use your TensorFlow Lite model in your app, first use the Firebase ML SDK to download the latest version of the model to the device. Then, instantiate a TensorFlow Lite interpreter with the model.To start the model download, call the model downloader's getModel()
method,
specifying the name you assigned the model when you uploaded it, whether you
want to always download the latest model, and the conditions under which you
want to allow downloading.
You can choose from three download behaviors:
| Download type | Description |
|---|---|
| LOCAL_MODEL | Get the local model from the device.
If there is no local model available, this
behaves like LATEST_MODEL
. Use this
download type if you are not interested in
checking for model updates. For example,
you're using Remote Config to retrieve
model names and you always upload models
under new names (recommended). |
| LOCAL_MODEL_UPDATE_IN_BACKGROUND | Get the local model from the device and
start updating the model in the background.
If there is no local model available, this
behaves like LATEST_MODEL
. |
| LATEST_MODEL | Get the latest model. If the local model is the latest version, returns the local model. Otherwise, download the latest model. This behavior will block until the latest version is downloaded (not recommended). Use this behavior only in cases where you explicitly need the latest version. |
You should disable model-related functionality—for example, grey-out or hide part of your UI—until you confirm the model has been downloaded.
Kotlin
val
conditions
=
CustomModelDownloadConditions
.
Builder
()
.
requireWifi
()
// Also possible: .requireCharging() and .requireDeviceIdle()
.
build
()
FirebaseModelDownloader
.
getInstance
()
.
getModel
(
"your_model"
,
DownloadType
.
LOCAL_MODEL_UPDATE_IN_BACKGROUND
,
conditions
)
.
addOnSuccessListener
{
model
:
CustomModel?
-
>
// Download complete. Depending on your app, you could enable the ML
// feature, or switch from the local model to the remote model, etc.
// The CustomModel object contains the local path of the model file,
// which you can use to instantiate a TensorFlow Lite interpreter.
val
modelFile
=
model
?.
file
if
(
modelFile
!=
null
)
{
interpreter
=
Interpreter
(
modelFile
)
}
}
Java
CustomModelDownloadConditions
conditions
=
new
CustomModelDownloadConditions
.
Builder
()
.
requireWifi
()
// Also possible: .requireCharging() and .requireDeviceIdle()
.
build
();
FirebaseModelDownloader
.
getInstance
()
.
getModel
(
"your_model"
,
DownloadType
.
LOCAL_MODEL_UPDATE_IN_BACKGROUND
,
conditions
)
.
addOnSuccessListener
(
new
OnSuccessListener<CustomModel>
()
{
@Override
public
void
onSuccess
(
CustomModel
model
)
{
// Download complete. Depending on your app, you could enable the ML
// feature, or switch from the local model to the remote model, etc.
// The CustomModel object contains the local path of the model file,
// which you can use to instantiate a TensorFlow Lite interpreter.
File
modelFile
=
model
.
getFile
();
if
(
modelFile
!=
null
)
{
interpreter
=
new
Interpreter
(
modelFile
);
}
}
});
Many apps start the download task in their initialization code, but you can do so at any point before you need to use the model.
3. Perform inference on input data
Get your model's input and output shapes
The TensorFlow Lite model interpreter takes as input and produces as output
one or more multidimensional arrays. These arrays contain either byte
, int
, long
, or float
values. Before you can pass data to a model or use its result, you must know
the number and dimensions ("shape") of the arrays your model uses.
If you built the model yourself, or if the model's input and output format is documented, you might already have this information. If you don't know the shape and data type of your model's input and output, you can use the TensorFlow Lite interpreter to inspect your model. For example:
Python
import tensorflow as tf interpreter = tf . lite . Interpreter ( model_path = "your_model.tflite" ) interpreter . allocate_tensors () # Print input shape and type inputs = interpreter . get_input_details () print ( ' {} input(s):' . format ( len ( inputs ))) for i in range ( 0 , len ( inputs )): print ( ' {} {} ' . format ( inputs [ i ][ 'shape' ], inputs [ i ][ 'dtype' ])) # Print output shape and type outputs = interpreter . get_output_details () print ( ' \n {} output(s):' . format ( len ( outputs ))) for i in range ( 0 , len ( outputs )): print ( ' {} {} ' . format ( outputs [ i ][ 'shape' ], outputs [ i ][ 'dtype' ]))
Example output:
1 input(s): [ 1 224 224 3] <class 'numpy.float32'> 1 output(s): [1 1000] <class 'numpy.float32'>
Run the interpreter
After you have determined the format of your model's input and output, get your input data and perform any transformations on the data that are necessary to get an input of the right shape for your model.For example, if you have an image classification model with an input shape of [1 224 224 3]
floating-point values, you could generate an input ByteBuffer
from a Bitmap
object as shown in the following example:
Kotlin
val
bitmap
=
Bitmap
.
createScaledBitmap
(
yourInputImage
,
224
,
224
,
true
)
val
input
=
ByteBuffer
.
allocateDirect
(
224
*
224
*
3
*
4
).
order
(
ByteOrder
.
nativeOrder
())
for
(
y
in
0
until
224
)
{
for
(
x
in
0
until
224
)
{
val
px
=
bitmap
.
getPixel
(
x
,
y
)
// Get channel values from the pixel value.
val
r
=
Color
.
red
(
px
)
val
g
=
Color
.
green
(
px
)
val
b
=
Color
.
blue
(
px
)
// Normalize channel values to [-1.0, 1.0]. This requirement depends on the model.
// For example, some models might require values to be normalized to the range
// [0.0, 1.0] instead.
val
rf
=
(
r
-
127
)
/
255f
val
gf
=
(
g
-
127
)
/
255f
val
bf
=
(
b
-
127
)
/
255f
input
.
putFloat
(
rf
)
input
.
putFloat
(
gf
)
input
.
putFloat
(
bf
)
}
}
Java
Bitmap
bitmap
=
Bitmap
.
createScaledBitmap
(
yourInputImage
,
224
,
224
,
true
);
ByteBuffer
input
=
ByteBuffer
.
allocateDirect
(
224
*
224
*
3
*
4
).
order
(
ByteOrder
.
nativeOrder
());
for
(
int
y
=
0
;
y
<
224
;
y
++
)
{
for
(
int
x
=
0
;
x
<
224
;
x
++
)
{
int
px
=
bitmap
.
getPixel
(
x
,
y
);
// Get channel values from the pixel value.
int
r
=
Color
.
red
(
px
);
int
g
=
Color
.
green
(
px
);
int
b
=
Color
.
blue
(
px
);
// Normalize channel values to [-1.0, 1.0]. This requirement depends
// on the model. For example, some models might require values to be
// normalized to the range [0.0, 1.0] instead.
float
rf
=
(
r
-
127
)
/
255.0f
;
float
gf
=
(
g
-
127
)
/
255.0f
;
float
bf
=
(
b
-
127
)
/
255.0f
;
input
.
putFloat
(
rf
);
input
.
putFloat
(
gf
);
input
.
putFloat
(
bf
);
}
}
Then, allocate a ByteBuffer
large enough to contain the model's output and
pass the input buffer and output buffer to the TensorFlow Lite interpreter's run()
method. For example, for an output shape of [1 1000]
floating-point
values:
Kotlin
val
bufferSize
=
1000
*
java
.
lang
.
Float
.
SIZE
/
java
.
lang
.
Byte
.
SIZE
val
modelOutput
=
ByteBuffer
.
allocateDirect
(
bufferSize
).
order
(
ByteOrder
.
nativeOrder
())
interpreter
?.
run
(
input
,
modelOutput
)
Java
int
bufferSize
=
1000
*
java
.
lang
.
Float
.
SIZE
/
java
.
lang
.
Byte
.
SIZE
;
ByteBuffer
modelOutput
=
ByteBuffer
.
allocateDirect
(
bufferSize
).
order
(
ByteOrder
.
nativeOrder
());
interpreter
.
run
(
input
,
modelOutput
);
How you use the output depends on the model you are using.
For example, if you are performing classification, as a next step, you might map the indexes of the result to the labels they represent:
Kotlin
modelOutput
.
rewind
()
val
probabilities
=
modelOutput
.
asFloatBuffer
()
try
{
val
reader
=
BufferedReader
(
InputStreamReader
(
assets
.
open
(
"custom_labels.txt"
)))
for
(
i
in
probabilities
.
capacity
())
{
val
label
:
String
=
reader
.
readLine
()
val
probability
=
probabilities
.
get
(
i
)
println
(
"
$
label
:
$
probability
"
)
}
}
catch
(
e
:
IOException
)
{
// File not found?
}
Java
modelOutput
.
rewind
();
FloatBuffer
probabilities
=
modelOutput
.
asFloatBuffer
();
try
{
BufferedReader
reader
=
new
BufferedReader
(
new
InputStreamReader
(
getAssets
().
open
(
"custom_labels.txt"
)));
for
(
int
i
=
0
;
i
<
probabilities
.
capacity
();
i
++
)
{
String
label
=
reader
.
readLine
();
float
probability
=
probabilities
.
get
(
i
);
Log
.
i
(
TAG
,
String
.
format
(
"%s: %1.4f"
,
label
,
probability
));
}
}
catch
(
IOException
e
)
{
// File not found?
}
Appendix: Model security
Regardless of how you make your TensorFlow Lite models available to Firebase ML , Firebase ML stores them in the standard serialized protobuf format in local storage.
In theory, this means that anybody can copy your model. However, in practice, most models are so application-specific and obfuscated by optimizations that the risk is similar to that of competitors disassembling and reusing your code. Nevertheless, you should be aware of this risk before you use a custom model in your app.
On Android API level 21 (Lollipop) and newer, the model is downloaded to a directory that is excluded from automatic backup .
On Android API level 20 and older, the model is downloaded to a directory
named com.google.firebase.ml.custom.models
in app-private
internal storage. If you enabled file backup using BackupAgent
,
you might choose to exclude this directory.
