// Copyright (c) 2018, Apple Inc. All rights reserved.
//
// Use of this source code is governed by a BSD-3-clause license that can be
// found in LICENSE.txt or at https://opensource.org/licenses/BSD-3-Clause
syntax = "proto3";
option optimize_for = LITE_RUNTIME;
import public "DataStructures.proto";
package CoreML.Specification;
/*
* Non-maximum suppression of axis-aligned bounding boxes.
*
* This is used primarily for object detectors that tend to produce multiple
* boxes around a single object. This is a byproduct of the detector's
* robustness to spatial translation. If there are two or more bounding boxes
* that are very similar to one another, the algorithm should return only a
* single representative.
*
* Similarity between two bounding boxes is measured by intersection-over-union
* (IOU), the fraction between the area of intersection and area of the union.
* Here is an example where the areas can be calculated by hand by counting
* glyphs::
*
* +-------+ +-------+
* | | | |
* | +------+ +--+ | +---+
* | | | | | | | |
* +-------+ | +--+ +----+ |
* | | | |
* +------+ +------+
* Intersection Union
* IOU: 0.16 = 12 / 73
*
* All IOU scores are fractions betwen 0.0 (fully disjoint) and 1.0 (perfect
* overlap). The standard algorithm (PickTop) is defined as follows:
*
* 1. Sort boxes by descending order of confidence
* 2. Take the top one and mark it as keep
* 3. Suppress (mark it as discard) all boxes within a fixed IOU radius of the
* keep box
* 4. Go to 2 and repeat on the subset of boxes not already kept or discarded
* 5. When all boxes are processed, output only the ones marked as keep
*
* Before the algorithm, boxes that fall below the confidence threshold are
* discarded.
*/
message NonMaximumSuppression {
// Suppression methods:
/*
* Pick the bounding box of the top confidence, suppress all within a radius.
*/
message PickTop {
/*
* Suppression is only done among predictions with the same label
* (argmax of the confidence).
*/
bool perClass = 1;
}
/*
* Choose which underlying suppression method to use
*/
oneof SuppressionMethod {
PickTop pickTop = 1;
}
/*
* Optional class label mapping.
*/
oneof ClassLabels {
StringVector stringClassLabels = 100;
Int64Vector int64ClassLabels = 101;
}
/*
* This defines the radius of suppression. A box is considered to be within
* the radius of another box if their IOU score is less than this value.
*/
double iouThreshold = 110;
/*
* Remove bounding boxes below this threshold. The algorithm run-time is
* proportional to the square of the number of incoming bounding boxes
* (O(N^2)). This threshold is a way to reduce N to make the algorithm
* faster. The confidence threshold can be any non-negative value. Negative
* confidences are not allowed, since if the output shape is specified to be
* larger than boxes after suppression, the unused boxes are filled with
* zero confidence. If the prediction is handled by Core Vision, it is also
* important that confidences are defined with the following semantics:
*
* 1. Confidences should be between 0 and 1
* 2. The sum of the confidences for a prediction should not exceed 1, but is
* allowed to be less than 1
* 3. The sum of the confidences will be interpreted as the confidence of
* any object (e.g. if the confidences for two classes are 0.2 and 0.4,
it means there is a 60% (0.2 + 0.4) confidence that an object is
present)
*/
double confidenceThreshold = 111;
/*
* Set the name of the confidence input.
*
* The input should be a multi-array of type double and shape N x C. N is
* the number of boxes and C the number of classes. Each row describes the
* confidences of each object category being present at that particular
* location. Confidences should be nonnegative, where 0.0 means the highest
* certainty the object is not present.
*
* Specifying shape is optional.
*/
string confidenceInputFeatureName = 200;
/*
* Set the name of the coordinates input.
*
* The input should be a multi-array of type double and shape N x 4. The
* rows correspond to the rows of the confidence matrix. The four values
* describe (in order):
*
* - x (center location of the box along the horizontal axis)
* - y (center location of the box along the vertical axis)
* - width (size of box along the horizontal axis)
* - height (size of box on along the vertical axis)
*
* Specifying shape is optional.
*/
string coordinatesInputFeatureName = 201;
/*
* The iouThreshold can be optionally overridden by specifying this string
* and providing a corresponding input of type double. This allows changing
* the value of the parameter during run-time.
*
* The input should be a scalar double between 0.0 and 1.0. Setting it to 1.0
* means there will be no suppression based on IOU.
*/
string iouThresholdInputFeatureName = 202;
/*
* The confidenceThreshold can be optionally overridden by specifying this
* string and providing a corresponding input. This allows changing the
* value of the parameter during run-time, which can aid setting it just
* right for a particular use case.
*
* The input should be a scalar double with nonnegative value.
*/
string confidenceThresholdInputFeatureName = 203;
/*
* Set the name of the confidence output. The output will be the same type
* and shape as the corresponding input. The only difference is that the
* number of rows may have been reduced.
*
* Specifying shape is optional. One reason to specify shape is to limit
* the number of output boxes. This can be done is several ways:
*
* Fixed shape:
* The output can be pinned to a fixed set of boxes. If this number is larger
* than the number of boxes that would have been returned, the output is
* padded with zeros for both confidence and coordinates. Specifying a fixed
* shape can be done by setting either shape (deprecated) or allowedShapes set
* to fixedsize.
*
* Min/max:
* It is also possible to set both a minimum and a maximum. The same
* zero-padding as for fixed shape is applied when necessary. Setting min/max
* is done by defining two allowedShapes, where the first dimension uses a
* rangeofsizes defining lowerbound and upperbound.
*/
string confidenceOutputFeatureName = 210;
/*
* Set the name of the coordinates output. The output will be the same type
* and shape as the corresponding input. The only difference is that the
* number of rows may have been reduced.
*
* Specifying shape is optional. See confidence output for a more detailed
* description. Note that to achieve either fixed shape output or a
* constraint range of boxes, only one of confidence or coordinates need to
* set a shape. Both shapes are allowed to be defined, but in such case they
* have to be consistent along dimension 0.
*/
string coordinatesOutputFeatureName = 211;
}
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