Drawing Classification

The Drawing Classifier is a toolkit focused on solving the task of classifying input from the Apple Pencil and/or mouse/touch input. This is the first effort towards bridging the gap between the Apple Pencil 2 and Core ML, which will further empower App Developers to build intelligent apps. Given a drawing, the drawing classifier aims to classify the drawing as one of a pre-determined number of classes/labels.

Loading Data and Expected Data Format

The Quick, Draw! dataset is a crowd-sourced dataset that provides around 50 million labeled drawings for 345 classes.1 In this example, we use data for two of the 345 classes from "Quick,Draw!" -- square and triangle. Go to Data Preparation to create the square_triangle.sframe that we will use in the introductory example.

The feature in the input SFrame to the Drawing Classifier can have the following two formats:

  1. Bitmap-based drawings (dtype=turicreate.Image): Each bitmap-based drawing must be represented as an image of any size. The network takes in grayscale images of size 28x28. Images of any other colorspace will automatically be converted to grayscale and images of any other size will automatically be resized, by the toolkit.

  2. Stroke-based drawings (dtype=list): Each stroke-based drawing must be represented as a list of strokes, where each stroke must be represented as a list of points in the order that they were drawn. Each point must be represented as a dictionary with exactly two keys, "x" and "y", the values of which must be numerical, i.e. integer or float. Here is an example of a drawing with two strokes that have five points each:

example_drawing = [
    [
        {"x": 1.0, "y": 2.0},
        {"x": 2.0, "y": 2.0},
        {"x": 3.0, "y": 2.0},
        {"x": 4.0, "y": 2.0},
        {"x": 5.0, "y": 2.0}
    ], # end of first stroke
    [
        {"x": 10.0, "y": 10.0},
        {"x": 10.5, "y": 10.5},
        {"x": 11.0, "y": 11.0},
        {"x": 12.5, "y": 12.5},
        {"x": 15.0, "y": 15.0}
    ]
]

Introductory Example

In this example, our goal is to predict if the drawing is a square or a triangle. Go to Data Preparation to find out how to get bitmap_square_triangle.sframe or stroke_square_triangle.sframe).

import turicreate as tc

# Try any one of the following
SFRAME_PATH = "sframes/bitmap_square_triangle.sframe"
SFRAME_PATH = "sframes/stroke_square_triangle.sframe"

# Load the data
data =  tc.SFrame(SFRAME_PATH)

# Make a small train-test split since our toolkit is not very data-hungry 
# for 2 classes
train_data, test_data = data.random_split(0.7)

# Create a model
model = tc.drawing_classifier.create(train_data, 'label')

# Save predictions to an SArray
predictions = model.predict(test_data)

# Evaluate the model and save the results into a dictionary
metrics = model.evaluate(test_data)
print(metrics["accuracy"])

# Save the model for later use in Turi Create
model.save("square_triangle.model")

# Export for use in Core ML
model.export_coreml("MySquareTriangleClassifier.mlmodel")

Advanced Usage

Refer to the following chapters for:

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