centerface.py

import numpy as np
import cv2


class CenterFace(object):
    def __init__(self, height, width):
        self.net = cv2.dnn.readNetFromONNX('centerface.onnx')
        self.img_h_new, self.img_w_new, self.scale_h, self.scale_w = self.transform(height, width)

    def __call__(self, img, threshold=0.5):

        blob = cv2.dnn.blobFromImage(img, scalefactor=1.0, size=(self.img_w_new, self.img_h_new), mean=(0, 0, 0), swapRB=True, crop=False)
        self.net.setInput(blob)
        heatmap, height, offset = self.net.forward(["537", "538", "539"])
        dets = self.decode(heatmap, height, offset, (self.img_h_new, self.img_w_new), threshold=threshold)
        if len(dets) > 0:
            dets[:, 0:4:2] = dets[:, 0:4:2] / self.scale_w
            dets[:, 1:4:2] = dets[:, 1:4:2] / self.scale_h
        else:
            dets = np.empty(shape=[0, 5], dtype=np.float32)

        return dets

    def transform(self, h, w):
        img_h_new, img_w_new = int(np.ceil(h / 32) * 32), int(np.ceil(w / 32) * 32)
        scale_h, scale_w = img_h_new / h, img_w_new / w
        return img_h_new, img_w_new, scale_h, scale_w

    def decode(self, heatmap, scale, offset, size, threshold=0.1):
        heatmap = np.squeeze(heatmap)
        scale0, scale1 = scale[0, 0, :, :], scale[0, 1, :, :]
        offset0, offset1 = offset[0, 0, :, :], offset[0, 1, :, :]
        c0, c1 = np.where(heatmap > threshold)
        boxes = []
        if len(c0) > 0:
            for i in range(len(c0)):
                s0, s1 = np.exp(scale0[c0[i], c1[i]]) * 4, np.exp(scale1[c0[i], c1[i]]) * 4
                o0, o1 = offset0[c0[i], c1[i]], offset1[c0[i], c1[i]]
                s = heatmap[c0[i], c1[i]]
                x1, y1 = max(0, (c1[i] + o1 + 0.5) * 4 - s1 / 2), max(0, (c0[i] + o0 + 0.5) * 4 - s0 / 2)
                x1, y1 = min(x1, size[1]), min(y1, size[0])
                boxes.append([x1, y1, min(x1 + s1, size[1]), min(y1 + s0, size[0]), s])
            boxes = np.asarray(boxes, dtype=np.float32)
            keep = self.nms(boxes[:, :4], boxes[:, 4], 0.3)
            boxes = boxes[keep, :]
        return boxes

    def nms(self, boxes, scores, nms_thresh):
        x1 = boxes[:, 0]
        y1 = boxes[:, 1]
        x2 = boxes[:, 2]
        y2 = boxes[:, 3]
        areas = (x2 - x1) * (y2 - y1)
        order = np.argsort(scores)[::-1]
        num_detections = boxes.shape[0]
        suppressed = np.zeros((num_detections,), dtype=np.bool)
        for _i in range(num_detections):
            i = order[_i]
            if suppressed[i]:
                continue
            ix1 = x1[i]
            iy1 = y1[i]
            ix2 = x2[i]
            iy2 = y2[i]
            iarea = areas[i]

            for _j in range(_i + 1, num_detections):
                j = order[_j]
                if suppressed[j]:
                    continue

                xx1 = max(ix1, x1[j])
                yy1 = max(iy1, y1[j])
                xx2 = min(ix2, x2[j])
                yy2 = min(iy2, y2[j])
                w = max(0, xx2 - xx1)
                h = max(0, yy2 - yy1)

                inter = w * h
                ovr = inter / (iarea + areas[j] - inter)
                if ovr >= nms_thresh:
                    suppressed[j] = True
        keep = np.nonzero(suppressed == 0)[0]
        return keep