Recurrent neural network architectures which provide text describing images

1. A method, performed by a computing device, for providing an output phrase describing an image, the method comprising:

creating feature maps describing image features in locations in the image, wherein the feature maps are created by processing the image with a convolutional neural network trained to extract the image features based on color values of pixels within the locations;

providing a skeletal phrase for the image including a first object word and a second object word, wherein:

the skeletal phrase is provided by processing the feature maps with a first long short-term memory (LSTM) neural network,

the first LSTM neural network trained to determine the skeletal phrase based on a first set of ground truth phrases, and

the first set of ground truth phrases comprising words that describe objects and relationships of the objects in a first set of ground truth images, without comprising words describing attributes;

providing attribute words for the image, wherein the attribute words are provided by processing the skeletal phrase and the feature maps with a second LSTM neural network, and the second LSTM neural network is trained to determine the attribute words based on a second set of ground truth phrases comprising words for attributes in a second set of ground truth images, wherein the attribute words includes a first attribute word and a second attribute word; and

providing the output phrase describing the image, wherein the output phrase includes the first attribute word modifying the first object word, and the second attribute word modifying the second object word.

2. The method of claim 1 , wherein providing the attribute words for the image comprises providing the output phrase as a whole using the second LSTM neural network.

3. The method of claim 1 , further comprising training the first LSTM neural network, wherein the training includes:

parsing, using a natural language parser, original ground truth phrases describing the first set of ground truth images to identify the attribute words; and

creating the first set of ground truth phrases from the original ground truth phrases by removing the attribute words from the original ground truth phrases.

4. The method of claim 1 , wherein providing the attribute words for the image further comprises processing a hidden state of the first LSTM neural network to provide the attribute words, and the hidden state identifies at least a portion of the skeletal phrase.

5. The method of claim 1 , wherein providing the attribute words for the image further comprises providing the attribute words by processing, using the second LSTM neural network, a weighted last time-step hidden state of the first LSTM neural network, and a weighted version of the feature maps.

6. The method of claim 1 , wherein providing the output phrase comprises displaying the output phrase on a display.

7. The method of claim 1 , further comprising:

generating attention maps associating skeletal words of the skeletal phrase with the locations in the image; and

refining the attention maps after providing the skeletal word describing the image feature based on the skeletal phrase, wherein the attribute words are provided based on the refined attention maps.

8. The method of claim 1 , wherein creating the feature maps further comprises:

representing, with data describing a respective pointwise mutual information word vector, each tag described in tag data;

calculating, using the data describing each of the respective pointwise mutual information word vectors and data describing a respective weight for each tag, data describing a weighted average of the pointwise mutual information word vectors; and

creating, based at least in part on the data describing the weighted average of the pointwise mutual information word vectors, the feature maps.

9. The method of claim 1 , further comprising verifying an accuracy of a skeletal word in the skeletal phrase by:

performing a k-nearest neighbor search on the first set of ground truth images for nearest neighbor objects of an object described by the skeletal word; and

identifying a similarity of titles of the nearest neighbor objects with the skeletal word.

10. The method of claim 1 , further comprising controlling a quantity of words in the output phrase by suppressing or increasing a probability of an end-of-phrase token in at least one of providing the skeletal phrase or providing the attribute words.

11. A system for providing an output phrase describing an image comprising:

at least one processor; and

a non-transitory computer-readable storage medium storing instructions that are executable by the at least one processor, the instructions being configured, when executed by the at least one processor to:

create feature maps describing image features in locations in the image, wherein the feature maps are created by processing the image with a convolutional neural network trained to extract the image features based on values of pixels within the locations;

provide a skeletal phrase for the image including a first object word and a second object word, wherein the skeletal phrase is provided by processing the feature maps with a first long short-term memory (LSTM) neural network;

provide attribute words for the image, wherein the attribute words are provided by processing the skeletal phrase and the feature maps with a second LSTM neural network, and wherein the attribute words include a first attribute word and a second attribute word; and

provide the output phrase describing the image, wherein the output phrase includes the first attribute word modifying the first object word, and the second attribute word modifying the second object word.

12. The system of claim 11 , wherein the instructions, when executed by the at least one processor, cause the at least one processor to provide the attribute words for the image including providing the output phrase as a whole using the second LSTM neural network.

13. The system of claim 11 , wherein the instructions, when executed by the at least one processor, cause the at least one processor to train the first LSTM neural network, including:

parsing, using a natural language parser, original ground truth phrases describing a first set of ground truth images to identify the attribute words;

creating a first set of ground truth phrases from the original ground truth phrases by removing the attribute words from the original ground truth phrases; and

training the first LSTM neural network to determine the skeletal phrase based on the first set of ground truth phrases.

14. The system of claim 11 , wherein the instructions, when executed by the at least one processor, cause the at least one processor to provide the attribute words for the image including processing a hidden state of the first LSTM neural network to provide the attribute words, and the hidden state identifies at least a portion of the skeletal phrase.

15. The system of claim 11 , wherein the instructions, when executed by the at least one processor, cause the at least one processor to provide the attribute words for the image, including providing the attribute words by processing, using the second LSTM neural network, a weighted last time-step hidden state of the first LSTM neural network, and a weighted version of the feature maps.

16. The system of claim 11 , wherein the instructions, when executed by the at least one processor, cause the at least one processor to:

generate attention maps associating skeletal words of the skeletal phrase with the locations in the image; and

refine the attention maps after providing the skeletal word describing the image feature based on the skeletal phrase, wherein the attribute words are provided based on the refined attention maps.

17. A non-transitory computer-readable medium storing instructions for providing an output phrase describing an image, the instructions comprising instructions for:

creating feature maps describing image features in locations in the image, wherein the feature maps are created by processing the image with a convolutional neural network trained to extract the image features based on values of pixels within the locations;

providing a skeletal phrase for the image including a first object word and a second object word, wherein:

the skeletal phrase is provided by processing the feature maps with a first long short-term memory (LSTM) neural network,

the first LSTM neural network is trained to determine the skeletal phrase based on a first set of ground truth phrases, and

the first set of ground truth phrases comprises words describing objects and relationships of the objects in a first set of ground truth images, without comprising words describing attributes;

providing attribute words for the image, wherein the attribute words are provided by processing the skeletal phrase and the feature maps with a second LSTM neural network, and the second LSTM neural network is trained to determine the attribute words based on a second set of ground truth phrases, wherein the attribute words includes a first attribute word and a second attribute word; and

providing the output phrase describing the image, wherein the output phrase includes the first attribute word modifying the first object word, and the second attribute word modifying the second object word.

18. The non-transitory computer-readable medium of claim 17 , wherein the instructions further include instructions for training the first LSTM neural network, including instructions for:

parsing, using a natural language parser, original ground truth phrases describing the first set of ground truth images to identify the attribute words; and

creating the first set of ground truth phrases from the original ground truth phrases by removing the attribute words from the original ground truth phrases.

19. The non-transitory computer-readable medium of claim 17 , wherein the instructions for providing the attribute words for the image further comprise instructions for processing a hidden state of the first LSTM neural network to provide the attribute words, and the hidden state identifies at least a portion of the skeletal phrase.

20. The non-transitory computer-readable medium of claim 17 , wherein the instructions further include instructions for:

generating attention maps associating skeletal words of the skeletal phrase with the locations in the image; and

refining the attention maps after providing the skeletal word describing the image feature based on the skeletal phrase, wherein the attribute words are provided based on the refined attention maps.