mindspore.dataset.VOCDataset

class mindspore.dataset.VOCDataset(dataset_dir, task='Segmentation', usage='train', class_indexing=None, num_samples=None, num_parallel_workers=None, shuffle=None, decode=False, sampler=None, num_shards=None, shard_id=None, cache=None, extra_metadata=False, decrypt=None)

VOC(Visual Object Classes) dataset.

The generated dataset with different task setting has different output columns:

• task = Detection , output columns: [image, dtype=uint8] , [bbox, dtype=float32] , [label, dtype=uint32] , [difficult, dtype=uint32] , [truncate, dtype=uint32] .

• task = Segmentation , output columns: [image, dtype=uint8] , [target,dtype=uint8] .

Parameters

• dataset_dir (str) – Path to the root directory that contains the dataset.

• task (str, optional) – Set the task type of reading voc data, now only support 'Segmentation' or 'Detection'. Default: 'Segmentation'.

• usage (str, optional) – Set the task type of ImageSets. Default: 'train'. If task is 'Segmentation', image and annotation list will be loaded in ./ImageSets/Segmentation/usage + ".txt"; If task is 'Detection', image and annotation list will be loaded in ./ImageSets/Main/usage + ".txt"; if task and usage are not set, image and annotation list will be loaded in ./ImageSets/Segmentation/train.txt as default.

• class_indexing (dict, optional) – A str-to-int mapping from label name to index, only valid in 'Detection' task. Default: None , the folder names will be sorted alphabetically and each class will be given a unique index starting from 0.

• num_samples (int, optional) – The number of images to be included in the dataset. Default: None , all images.

• num_parallel_workers (int, optional) – Number of worker threads to read the data. Default: None , will use global default workers(8), it can be set by mindspore.dataset.config.set_num_parallel_workers() .

• shuffle (bool, optional) – Whether to perform shuffle on the dataset. Default: None , expected order behavior shown in the table below.

• decode (bool, optional) – Decode the images after reading. Default: False.

• sampler (Sampler, optional) – Object used to choose samples from the dataset. Default: None , expected order behavior shown in the table below.

• num_shards (int, optional) – Number of shards that the dataset will be divided into. Default: None . When this argument is specified, num_samples reflects the maximum sample number of per shard.

• shard_id (int, optional) – The shard ID within num_shards . Default: None . This argument can only be specified when num_shards is also specified.

• cache (DatasetCache, optional) – Use tensor caching service to speed up dataset processing. More details: Single-Node Data Cache . Default: None , which means no cache is used.

• extra_metadata (bool, optional) – Flag to add extra meta-data to row. If True, an additional column named [_meta-filename, dtype=string] will be output at the end. Default: False.

• decrypt (callable, optional) – Image decryption function, which accepts the path of the encrypted image file and returns the decrypted bytes data. Default: None , no decryption.

Raises

• RuntimeError – If dataset_dir does not contain data files.

• RuntimeError – If xml of Annotations is an invalid format.

• RuntimeError – If xml of Annotations loss attribution of object .

• RuntimeError – If xml of Annotations loss attribution of bndbox .

• RuntimeError – If sampler and shuffle are specified at the same time.

• RuntimeError – If sampler and num_shards/shard_id are specified at the same time.

• RuntimeError – If num_shards is specified but shard_id is None.

• RuntimeError – If shard_id is specified but num_shards is None.

• ValueError – If num_parallel_workers exceeds the max thread numbers.

• ValueError – If task is not equal 'Segmentation' or 'Detection'.

• ValueError – If task is 'Segmentation' but class_indexing is not None.

• ValueError – If txt related to mode is not exist.

• ValueError – If shard_id is not in range of [0, num_shards ).

Tutorial Examples:

• Load & Process Data With Dataset Pipeline

Note

• Column '[_meta-filename, dtype=string]' won't be output unless an explicit rename dataset op is added to remove the prefix('_meta-').

• The parameters num_samples , shuffle , num_shards , shard_id can be used to control the sampler used in the dataset, and their effects when combined with parameter sampler are as follows.

Sampler obtained by different combinations of parameters sampler and num_samples , shuffle , num_shards , shard_id

Parameter sampler	Parameter num_shards / shard_id	Parameter shuffle	Parameter num_samples	Sampler Used
mindspore.dataset.Sampler type	None	None	None	sampler
numpy.ndarray,list,tuple,int type	/	/	num_samples	SubsetSampler(indices = sampler , num_samples = num_samples )
iterable type	/	/	num_samples	IterSampler(sampler = sampler , num_samples = num_samples )
None	num_shards / shard_id	None / True	num_samples	DistributedSampler(num_shards = num_shards , shard_id = shard_id , shuffle = True , num_samples = num_samples )
None	num_shards / shard_id	False	num_samples	DistributedSampler(num_shards = num_shards , shard_id = shard_id , shuffle = False , num_samples = num_samples )
None	None	None / True	None	RandomSampler(num_samples = num_samples )
None	None	None / True	num_samples	RandomSampler(replacement = True , num_samples = num_samples )
None	None	False	num_samples	SequentialSampler(num_samples = num_samples )

Examples

>>> import mindspore.dataset as ds
>>> voc_dataset_dir = "/path/to/voc_dataset_directory"
>>>
>>> # 1) Read VOC data for segmentation training
>>> dataset = ds.VOCDataset(dataset_dir=voc_dataset_dir, task="Segmentation", usage="train")
>>>
>>> # 2) Read VOC data for detection training
>>> dataset = ds.VOCDataset(dataset_dir=voc_dataset_dir, task="Detection", usage="train")
>>>
>>> # 3) Read all VOC dataset samples in voc_dataset_dir with 8 threads in random order
>>> dataset = ds.VOCDataset(dataset_dir=voc_dataset_dir, task="Detection", usage="train",
...                         num_parallel_workers=8)
>>>
>>> # 4) Read then decode all VOC dataset samples in voc_dataset_dir in sequence
>>> dataset = ds.VOCDataset(dataset_dir=voc_dataset_dir, task="Detection", usage="train",
...                         decode=True, shuffle=False)
>>>
>>> # In VOC dataset, if task='Segmentation', each dictionary has keys "image" and "target"
>>> # In VOC dataset, if task='Detection', each dictionary has keys "image" and "annotation"

About VOC dataset:

The PASCAL Visual Object Classes (VOC) challenge is a benchmark in visual object category recognition and detection, providing the vision and machine learning communities with a standard dataset of images and annotation, and standard evaluation procedures.

You can unzip the original VOC-2012 dataset files into this directory structure and read by MindSpore's API.

.
└── voc2012_dataset_dir
    ├── Annotations
    │    ├── 2007_000027.xml
    │    ├── 2007_000032.xml
    │    ├── ...
    ├── ImageSets
    │    ├── Action
    │    ├── Layout
    │    ├── Main
    │    └── Segmentation
    ├── JPEGImages
    │    ├── 2007_000027.jpg
    │    ├── 2007_000032.jpg
    │    ├── ...
    ├── SegmentationClass
    │    ├── 2007_000032.png
    │    ├── 2007_000033.png
    │    ├── ...
    └── SegmentationObject
         ├── 2007_000032.png
         ├── 2007_000033.png
         ├── ...

Citation:

@article{Everingham10,
author       = {Everingham, M. and Van~Gool, L. and Williams, C. K. I. and Winn, J. and Zisserman, A.},
title        = {The Pascal Visual Object Classes (VOC) Challenge},
journal      = {International Journal of Computer Vision},
volume       = {88},
year         = {2012},
number       = {2},
month        = {jun},
pages        = {303--338},
biburl       = {http://host.robots.ox.ac.uk/pascal/VOC/pubs/everingham10.html#bibtex},
howpublished = {http://host.robots.ox.ac.uk/pascal/VOC/voc2012/index.html}
}

Pre-processing Operation

mindspore.dataset.Dataset.apply	Apply a function in this dataset.
mindspore.dataset.Dataset.concat	Concatenate the dataset objects in the input list.
mindspore.dataset.Dataset.filter	Filter dataset by prediction.
mindspore.dataset.Dataset.flat_map	Map func to each row in dataset and flatten the result.
mindspore.dataset.Dataset.map	Apply each operation in operations to this dataset.
mindspore.dataset.Dataset.project	The specified columns will be selected from the dataset and passed into the pipeline with the order specified.
mindspore.dataset.Dataset.rename	Rename the columns in input datasets.
mindspore.dataset.Dataset.repeat	Repeat this dataset count times.
mindspore.dataset.Dataset.reset	Reset the dataset for next epoch.
mindspore.dataset.Dataset.save	Save the dynamic data processed by the dataset pipeline in common dataset format.
mindspore.dataset.Dataset.shuffle	Shuffle the dataset by creating a cache with the size of buffer_size .
mindspore.dataset.Dataset.skip	Skip the first N elements of this dataset.
mindspore.dataset.Dataset.split	Split the dataset into smaller, non-overlapping datasets.
mindspore.dataset.Dataset.take	Take the first specified number of samples from the dataset.
mindspore.dataset.Dataset.zip	Zip the datasets in the sense of input tuple of datasets.

Batch

mindspore.dataset.Dataset.batch	Combine batch_size number of consecutive rows into batch which apply per_batch_map to the samples first.
mindspore.dataset.Dataset.bucket_batch_by_length	Bucket elements according to their lengths.
mindspore.dataset.Dataset.padded_batch	Combine batch_size number of consecutive rows into batch which apply pad_info to the samples first.

Iterator

mindspore.dataset.Dataset.create_dict_iterator	Create an iterator over the dataset that yields samples of type dict, while the key is the column name and the value is the data.
mindspore.dataset.Dataset.create_tuple_iterator	Create an iterator over the dataset that yields samples of type list, whose elements are the data for each column.

Attribute

mindspore.dataset.Dataset.get_batch_size	Return the size of batch.
mindspore.dataset.Dataset.get_class_indexing	Get the mapping dictionary from category names to category indexes.
mindspore.dataset.Dataset.get_col_names	Return the names of the columns in dataset.
mindspore.dataset.Dataset.get_dataset_size	Return the number of batches in an epoch.
mindspore.dataset.Dataset.get_repeat_count	Get the replication times in RepeatDataset.
mindspore.dataset.Dataset.input_indexs	Get the column index, which represents the corresponding relationship between the data column order and the network when using the sink mode.
mindspore.dataset.Dataset.num_classes	Get the number of classes in a dataset.
mindspore.dataset.Dataset.output_shapes	Get the shapes of output data.
mindspore.dataset.Dataset.output_types	Get the types of output data.

Apply Sampler

mindspore.dataset.MappableDataset.add_sampler	Add a child sampler for the current dataset.
mindspore.dataset.MappableDataset.use_sampler	Replace the last child sampler of the current dataset, remaining the parent sampler unchanged.

Others

mindspore.dataset.Dataset.sync_update	Release a blocking condition and trigger callback with given data.
mindspore.dataset.Dataset.sync_wait	Add a blocking condition to the input Dataset and a synchronize action will be applied.
mindspore.dataset.Dataset.to_json	Serialize a pipeline into JSON string and dump into file if filename is provided.