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Mask R-CNN

Description

This model is a real-time neural network for object instance segmentation that detects 80 different classes.

Model

Model Download Download (with sample test data) ONNX version Opset version Accuracy
Mask R-CNN R-50-FPN 177.9 MB 168.8 MB 1.5 10 mAP of 0.36 & 0.33

Inference

Input to model

Image shape (3x'height'x'width')

Preprocessing steps

The images have to be loaded in to a range of [0, 255], resized, converted to BGR and then normalized using mean = [102.9801, 115.9465, 122.7717]. The transformation should preferably happen at preprocessing.

This model can take images of different sizes as input. However, to achieve best performance, it is recommended to resize the image such that both height and width are within the range of [800, 1333], and then pad the image with zeros such that both height and width are divisible by 32.

The following code shows how to preprocess the demo image:

import numpy as np
from PIL import Image

def preprocess(image):
    # Resize
    ratio = 800.0 / min(image.size[0], image.size[1])
    image = image.resize((int(ratio * image.size[0]), int(ratio * image.size[1])), Image.BILINEAR)

    # Convert to BGR
    image = np.array(image)[:, :, [2, 1, 0]].astype('float32')

    # HWC -> CHW
    image = np.transpose(image, [2, 0, 1])

    # Normalize
    mean_vec = np.array([102.9801, 115.9465, 122.7717])
    for i in range(image.shape[0]):
        image[i, :, :] = image[i, :, :] - mean_vec[i]

    # Pad to be divisible of 32
    import math
    padded_h = int(math.ceil(image.shape[1] / 32) * 32)
    padded_w = int(math.ceil(image.shape[2] / 32) * 32)

    padded_image = np.zeros((3, padded_h, padded_w), dtype=np.float32)
    padded_image[:, :image.shape[1], :image.shape[2]] = image
    image = padded_image

    return image

img = Image.open('dependencies/demo.jpg')
img_data = preprocess(img)

Output of model

The model has 4 outputs.

boxes: ('nbox'x4), in (xmin, ymin, xmax, ymax).

labels: ('nbox').

scores: ('nbox').

masks: ('nbox', 1, 28, 28).

Postprocessing steps

The following code shows how to patch the original image with detections, class annotations and segmentation, filtered by scores:

import matplotlib.pyplot as plt
import matplotlib.patches as patches

import pycocotools.mask as mask_util
import cv2

classes = [line.rstrip('\n') for line in open('coco_classes.txt')]

def display_objdetect_image(image, boxes, labels, scores, masks, score_threshold=0.7):
    # Resize boxes
    ratio = 800.0 / min(image.size[0], image.size[1])
    boxes /= ratio

    _, ax = plt.subplots(1, figsize=(12,9))

    image = np.array(image)

    for mask, box, label, score in zip(masks, boxes, labels, scores):
        # Showing boxes with score > 0.7
        if score <= score_threshold:
            continue

        # Finding contour based on mask
        mask = mask[0, :, :, None]
        int_box = [int(i) for i in box]
        mask = cv2.resize(mask, (int_box[2]-int_box[0]+1, int_box[3]-int_box[1]+1))
        mask = mask > 0.5
        im_mask = np.zeros((image.shape[0], image.shape[1]), dtype=np.uint8)
        x_0 = max(int_box[0], 0)
        x_1 = min(int_box[2] + 1, image.shape[1])
        y_0 = max(int_box[1], 0)
        y_1 = min(int_box[3] + 1, image.shape[0])
        mask_y_0 = max(y_0 - box[1], 0)
        mask_y_1 = mask_y_0 + y_1 - y_0
        mask_x_0 = max(x_0 - box[0], 0)
        mask_x_1 = mask_x_0 + x_1 - x_0
        im_mask[y_0:y_1, x_0:x_1] = mask[
            mask_y_0 : mask_y_1, mask_x_0 : mask_x_1
        ]
        im_mask = im_mask[:, :, None]

        # OpenCV version 4.x
        contours, hierarchy = cv2.findContours(
            im_mask, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE
        )

        image = cv2.drawContours(image, contours, -1, 25, 3)

        rect = patches.Rectangle((box[0], box[1]), box[2] - box[0], box[3] - box[1], linewidth=1, edgecolor='b', facecolor='none')
        ax.annotate(classes[label] + ':' + str(np.round(score, 2)), (box[0], box[1]), color='w', fontsize=12)
        ax.add_patch(rect)

    ax.imshow(image)
    plt.show()

display_objdetect_image(img, boxes, labels, scores, masks)

Dataset (Train and validation)

The original pretrained Mask R-CNN model is from facebookresearch/maskrcnn-benchmark, compute mAP the same as Detectron on coco_2014_minival dataset from COCO, which is exactly equivalent to the coco_2017_val dataset.

Validation accuracy

Metric is COCO mAP (averaged over IoU of 0.5:0.95), computed over 2017 COCO val data. box mAP of 0.361, and mask mAP of 0.327.

Publication/Attribution

Kaiming He, Georgia Gkioxari, Piotr Dollár, and Ross Girshick. Mask R-CNN. IEEE International Conference on Computer Vision (ICCV), 2017.

Massa, Francisco and Girshick, Ross. maskrcnn-benchmark: Fast, modular reference implementation of Instance Segmentation and Object Detection algorithms in PyTorch. facebookresearch/maskrcnn-benchmark.

References

This model is converted from facebookresearch/maskrcnn-benchmark with modifications in repository.

License

MIT License