# IMAGE\_TO\_NDARRAY

`ImageToNDArrayStep` is a `PipelineStep` for converting images to n-dimensional arrays. The exact way that images are converted is highly configurable (formats, channels, output sizes, normalization, etc).

| Configs         | Descriptions                                                                                                                                      |
| --------------- | ------------------------------------------------------------------------------------------------------------------------------------------------- |
| config          | Configuration for how conversion should be performed.                                                                                             |
| keys            | May be null. If non-null, these are the names of images in the Data instance to convert.                                                          |
| outputNames     | May be null. If non-null, the input images are renamed to this in the output Data instance after conversion to n-dimensional array.               |
| keepOtherValues | True by default. If true, copy all the other (non-converted/non-image) entries in the input data to the output data.                              |
| metadata        | False by default. If true, include metadata about the images in the output data. For example, if/how it was cropped, and the original input size. |
| metadataKey     | Sets the key that the metadata will be stored under. Not relevant if metadata == `false`. Default is `@ImageToNDArrayStepMetadata`                |

`ImageToNDArrayConfig` is configuration for converting an image into n-dimensional array. This configuration is used in `config` from `ImageToNDArrayStep`, for example:

```
inferenceConfiguration.pipeline(SequencePipeline.builder()
                .add(new ImageToNDArrayStep() //add ImageToNDArrayStep() into pipeline to set image to NDArray for input
                        .config(new ImageToNDArrayConfig() //image configuration
                                .width(28)
                                .height(28)
                                .dataType(NDArrayType.FLOAT)
                                .aspectRatioHandling(AspectRatioHandling.CENTER_CROP)
                                .includeMinibatchDim(true)
                                .channelLayout(NDChannelLayout.GRAYSCALE)
                                .format(NDFormat.CHANNELS_FIRST)
                                .normalization(ImageNormalization.builder().type(ImageNormalization.Type.SCALE).build())
                        )
                        .keys("image")
                        .outputNames("input_layer")
                        .keepOtherValues(true)
                        .metadata(false)
                        .metadataKey(ImageToNDArrayStep.DEFAULT_METADATA_KEY))
                .build()
```

| Configs             | Descriptions                                                                                                                                                                                                                                                                                                                                                             |
| ------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| height              | Output array image height. Leave null to convert to the same size as the image height.                                                                                                                                                                                                                                                                                   |
| width               | Output array image width. Leave null to convert to the same size as the image width.                                                                                                                                                                                                                                                                                     |
| dataType            | Data type of the n-dimensional array. Default value is `FLOAT`.                                                                                                                                                                                                                                                                                                          |
| includeMinibatchDim | If true, the output array will contain an extra dimension for the minibatch number. This will look like (1, Channels, Height, Width) instead of (Channels, Height, Width) for format == `CHANNELS_FIRST` or (1, Height, Width, Channels) instead of (Height, Width, Channels) for format == `CHANNELS_LAST`. Default is `true`.                                          |
| aspectRatioHandling | <p>An enum to Handle the situation where the input image and output NDArray have different aspect ratios. </p><p><code>CENTER\_CROP</code> (crop larger dimension then resize if necessary), <code>PAD</code> (pad smaller dimension then resize if necessary), <code>STRETCH</code> (simply resize, distorting if necessary). Default is <code>CENTER\_CROP</code>.</p> |
| format              | The format to be used when converting an Image to an NDArray. Default is `CHANNEL_FIRST`. Another option is `CHANNEL_LAST`.                                                                                                                                                                                                                                              |
| channelLayout       | An enum that represents the type (and order) of the color channels for an image after it has been converted to an NDArray. For example, `RGB` vs. `BGR` etc, default value is `RGB`.                                                                                                                                                                                     |
| normalization       | Configuration that specifies the normalization type of an image array values.                                                                                                                                                                                                                                                                                            |
| listHandling        | An enum to specify how to handle a list of input images. Default is `NONE`.                                                                                                                                                                                                                                                                                              |