Add histogram equalization fcn (#2049)

models/yolo.py

@@ -107,7 +107,7 @@ class Model(nn.Module):
             for si, fi in zip(s, f):
                 xi = scale_img(x.flip(fi) if fi else x, si, gs=int(self.stride.max()))
                 yi = self.forward_once(xi)[0]  # forward
-                # cv2.imwrite('img%g.jpg' % s, 255 * xi[0].numpy().transpose((1, 2, 0))[:, :, ::-1])  # save
+                # cv2.imwrite(f'img_{si}.jpg', 255 * xi[0].cpu().numpy().transpose((1, 2, 0))[:, :, ::-1])  # save
                 yi[..., :4] /= si  # de-scale
                 if fi == 2:
                     yi[..., 1] = img_size[0] - yi[..., 1]  # de-flip ud