"""YOLO_v3 Model Defined in Keras.""" from functools import wraps import numpy as np import tensorflow as tf from keras import backend as K from keras.layers import Conv2D, Add, ZeroPadding2D, UpSampling2D, Concatenate, MaxPooling2D from keras.layers import LeakyReLU from keras.layers import BatchNormalization from keras.models import Model from keras.regularizers import l2 from yolo3.utils import compose @wraps(Conv2D) def DarknetConv2D(*args, **kwargs): """Wrapper to set Darknet parameters for Convolution2D.""" darknet_conv_kwargs = {'kernel_regularizer': l2(5e-4)} darknet_conv_kwargs['padding'] = 'valid' if kwargs.get('strides')==(2,2) else 'same' darknet_conv_kwargs.update(kwargs) return Conv2D(*args, **darknet_conv_kwargs) def DarknetConv2D_BN_Leaky(*args, **kwargs): """Darknet Convolution2D followed by BatchNormalization and LeakyReLU.""" no_bias_kwargs = {'use_bias': False} no_bias_kwargs.update(kwargs) return compose( DarknetConv2D(*args, **no_bias_kwargs), BatchNormalization(), LeakyReLU(alpha=0.1)) def resblock_body(x, num_filters, num_blocks): '''A series of resblocks starting with a downsampling Convolution2D''' # Darknet uses left and top padding instead of 'same' mode x = ZeroPadding2D(((1,0),(1,0)))(x) x = DarknetConv2D_BN_Leaky(num_filters, (3,3), strides=(2,2))(x) for i in range(num_blocks): y = compose( DarknetConv2D_BN_Leaky(num_filters//2, (1,1)), DarknetConv2D_BN_Leaky(num_filters, (3,3)))(x) x = Add()([x,y]) return x def darknet_body(x): '''Darknent body having 52 Convolution2D layers''' x = DarknetConv2D_BN_Leaky(32, (3,3))(x) x = resblock_body(x, 64, 1) x = resblock_body(x, 128, 2) x = resblock_body(x, 256, 8) x = resblock_body(x, 512, 8) x = resblock_body(x, 1024, 4) return x def make_last_layers(x, num_filters, out_filters): '''6 Conv2D_BN_Leaky layers followed by a Conv2D_linear layer''' x = compose( DarknetConv2D_BN_Leaky(num_filters, (1,1)), DarknetConv2D_BN_Leaky(num_filters*2, (3,3)), DarknetConv2D_BN_Leaky(num_filters, (1,1)), DarknetConv2D_BN_Leaky(num_filters*2, (3,3)), DarknetConv2D_BN_Leaky(num_filters, (1,1)))(x) y = compose( DarknetConv2D_BN_Leaky(num_filters*2, (3,3)), DarknetConv2D(out_filters, (1,1)))(x) return x, y def yolo_body(inputs, num_anchors, num_classes): """Create YOLO_V3 model CNN body in Keras.""" darknet = Model(inputs, darknet_body(inputs)) x, y1 = make_last_layers(darknet.output, 512, num_anchors*(num_classes+5)) x = compose( DarknetConv2D_BN_Leaky(256, (1,1)), UpSampling2D(2))(x) x = Concatenate()([x,darknet.layers[152].output]) x, y2 = make_last_layers(x, 256, num_anchors*(num_classes+5)) x = compose( DarknetConv2D_BN_Leaky(128, (1,1)), UpSampling2D(2))(x) x = Concatenate()([x,darknet.layers[92].output]) x, y3 = make_last_layers(x, 128, num_anchors*(num_classes+5)) return Model(inputs, [y1,y2,y3]) def tiny_yolo_body(inputs, num_anchors, num_classes): '''Create Tiny YOLO_v3 model CNN body in keras.''' x1 = compose( DarknetConv2D_BN_Leaky(16, (3,3)), MaxPooling2D(pool_size=(2,2), strides=(2,2), padding='same'), DarknetConv2D_BN_Leaky(32, (3,3)), MaxPooling2D(pool_size=(2,2), strides=(2,2), padding='same'), DarknetConv2D_BN_Leaky(64, (3,3)), MaxPooling2D(pool_size=(2,2), strides=(2,2), padding='same'), DarknetConv2D_BN_Leaky(128, (3,3)), MaxPooling2D(pool_size=(2,2), strides=(2,2), padding='same'), DarknetConv2D_BN_Leaky(256, (3,3)))(inputs) x2 = compose( MaxPooling2D(pool_size=(2,2), strides=(2,2), padding='same'), DarknetConv2D_BN_Leaky(512, (3,3)), MaxPooling2D(pool_size=(2,2), strides=(1,1), padding='same'), DarknetConv2D_BN_Leaky(1024, (3,3)), DarknetConv2D_BN_Leaky(256, (1,1)))(x1) y1 = compose( DarknetConv2D_BN_Leaky(512, (3,3)), DarknetConv2D(num_anchors*(num_classes+5), (1,1)))(x2) x2 = compose( DarknetConv2D_BN_Leaky(128, (1,1)), UpSampling2D(2))(x2) y2 = compose( Concatenate(), DarknetConv2D_BN_Leaky(256, (3,3)), DarknetConv2D(num_anchors*(num_classes+5), (1,1)))([x2,x1]) return Model(inputs, [y1,y2]) def yolo_head(feats, anchors, num_classes, input_shape, calc_loss=False): """Convert final layer features to bounding box parameters.""" num_anchors = len(anchors) # Reshape to batch, height, width, num_anchors, box_params. anchors_tensor = K.reshape(K.constant(anchors), [1, 1, 1, num_anchors, 2]) grid_shape = K.shape(feats)[1:3] # height, width grid_y = K.tile(K.reshape(K.arange(0, stop=grid_shape[0]), [-1, 1, 1, 1]), [1, grid_shape[1], 1, 1]) grid_x = K.tile(K.reshape(K.arange(0, stop=grid_shape[1]), [1, -1, 1, 1]), [grid_shape[0], 1, 1, 1]) grid = K.concatenate([grid_x, grid_y]) grid = K.cast(grid, K.dtype(feats)) feats = K.reshape( feats, [-1, grid_shape[0], grid_shape[1], num_anchors, num_classes + 5]) # Adjust preditions to each spatial grid point and anchor size. box_xy = (K.sigmoid(feats[..., :2]) + grid) / K.cast(grid_shape[::-1], K.dtype(feats)) box_wh = K.exp(feats[..., 2:4]) * anchors_tensor / K.cast(input_shape[::-1], K.dtype(feats)) box_confidence = K.sigmoid(feats[..., 4:5]) box_class_probs = K.sigmoid(feats[..., 5:]) if calc_loss == True: return grid, feats, box_xy, box_wh return box_xy, box_wh, box_confidence, box_class_probs def yolo_correct_boxes(box_xy, box_wh, input_shape, image_shape): '''Get corrected boxes''' box_yx = box_xy[..., ::-1] box_hw = box_wh[..., ::-1] input_shape = K.cast(input_shape, K.dtype(box_yx)) image_shape = K.cast(image_shape, K.dtype(box_yx)) new_shape = K.round(image_shape * K.min(input_shape/image_shape)) offset = (input_shape-new_shape)/2./input_shape scale = input_shape/new_shape box_yx = (box_yx - offset) * scale box_hw *= scale box_mins = box_yx - (box_hw / 2.) box_maxes = box_yx + (box_hw / 2.) boxes = K.concatenate([ box_mins[..., 0:1], # y_min box_mins[..., 1:2], # x_min box_maxes[..., 0:1], # y_max box_maxes[..., 1:2] # x_max ]) # Scale boxes back to original image shape. boxes *= K.concatenate([image_shape, image_shape]) return boxes def yolo_boxes_and_scores(feats, anchors, num_classes, input_shape, image_shape): '''Process Conv layer output''' box_xy, box_wh, box_confidence, box_class_probs = yolo_head(feats, anchors, num_classes, input_shape) boxes = yolo_correct_boxes(box_xy, box_wh, input_shape, image_shape) boxes = K.reshape(boxes, [-1, 4]) box_scores = box_confidence * box_class_probs box_scores = K.reshape(box_scores, [-1, num_classes]) return boxes, box_scores def yolo_eval(yolo_outputs, anchors, num_classes, image_shape, max_boxes=20, score_threshold=.6, iou_threshold=.5): """Evaluate YOLO model on given input and return filtered boxes.""" num_layers = len(yolo_outputs) anchor_mask = [[6,7,8], [3,4,5], [0,1,2]] if num_layers==3 else [[3,4,5], [1,2,3]] # default setting input_shape = K.shape(yolo_outputs[0])[1:3] * 32 boxes = [] box_scores = [] for l in range(num_layers): _boxes, _box_scores = yolo_boxes_and_scores(yolo_outputs[l], anchors[anchor_mask[l]], num_classes, input_shape, image_shape) boxes.append(_boxes) box_scores.append(_box_scores) boxes = K.concatenate(boxes, axis=0) box_scores = K.concatenate(box_scores, axis=0) mask = box_scores >= score_threshold max_boxes_tensor = K.constant(max_boxes, dtype='int32') boxes_ = [] scores_ = [] classes_ = [] for c in range(num_classes): # TODO: use keras backend instead of tf. class_boxes = tf.boolean_mask(boxes, mask[:, c]) class_box_scores = tf.boolean_mask(box_scores[:, c], mask[:, c]) nms_index = tf.image.non_max_suppression( class_boxes, class_box_scores, max_boxes_tensor, iou_threshold=iou_threshold) class_boxes = K.gather(class_boxes, nms_index) class_box_scores = K.gather(class_box_scores, nms_index) classes = K.ones_like(class_box_scores, 'int32') * c boxes_.append(class_boxes) scores_.append(class_box_scores) classes_.append(classes) boxes_ = K.concatenate(boxes_, axis=0) scores_ = K.concatenate(scores_, axis=0) classes_ = K.concatenate(classes_, axis=0) return boxes_, scores_, classes_ def preprocess_true_boxes(true_boxes, input_shape, anchors, num_classes): '''Preprocess true boxes to training input format Parameters ---------- true_boxes: array, shape=(m, T, 5) Absolute x_min, y_min, x_max, y_max, class_id relative to input_shape. input_shape: array-like, hw, multiples of 32 anchors: array, shape=(N, 2), wh num_classes: integer Returns ------- y_true: list of array, shape like yolo_outputs, xywh are reletive value ''' assert (true_boxes[..., 4]0 for b in range(m): # Discard zero rows. wh = boxes_wh[b, valid_mask[b]] if len(wh)==0: continue # Expand dim to apply broadcasting. wh = np.expand_dims(wh, -2) box_maxes = wh / 2. box_mins = -box_maxes intersect_mins = np.maximum(box_mins, anchor_mins) intersect_maxes = np.minimum(box_maxes, anchor_maxes) intersect_wh = np.maximum(intersect_maxes - intersect_mins, 0.) intersect_area = intersect_wh[..., 0] * intersect_wh[..., 1] box_area = wh[..., 0] * wh[..., 1] anchor_area = anchors[..., 0] * anchors[..., 1] iou = intersect_area / (box_area + anchor_area - intersect_area) # Find best anchor for each true box best_anchor = np.argmax(iou, axis=-1) for t, n in enumerate(best_anchor): for l in range(num_layers): if n in anchor_mask[l]: i = np.floor(true_boxes[b,t,0]*grid_shapes[l][1]).astype('int32') j = np.floor(true_boxes[b,t,1]*grid_shapes[l][0]).astype('int32') k = anchor_mask[l].index(n) c = true_boxes[b,t, 4].astype('int32') y_true[l][b, j, i, k, 0:4] = true_boxes[b,t, 0:4] y_true[l][b, j, i, k, 4] = 1 y_true[l][b, j, i, k, 5+c] = 1 return y_true def box_iou(b1, b2): '''Return iou tensor Parameters ---------- b1: tensor, shape=(i1,...,iN, 4), xywh b2: tensor, shape=(j, 4), xywh Returns ------- iou: tensor, shape=(i1,...,iN, j) ''' # Expand dim to apply broadcasting. b1 = K.expand_dims(b1, -2) b1_xy = b1[..., :2] b1_wh = b1[..., 2:4] b1_wh_half = b1_wh/2. b1_mins = b1_xy - b1_wh_half b1_maxes = b1_xy + b1_wh_half # Expand dim to apply broadcasting. b2 = K.expand_dims(b2, 0) b2_xy = b2[..., :2] b2_wh = b2[..., 2:4] b2_wh_half = b2_wh/2. b2_mins = b2_xy - b2_wh_half b2_maxes = b2_xy + b2_wh_half intersect_mins = K.maximum(b1_mins, b2_mins) intersect_maxes = K.minimum(b1_maxes, b2_maxes) intersect_wh = K.maximum(intersect_maxes - intersect_mins, 0.) intersect_area = intersect_wh[..., 0] * intersect_wh[..., 1] b1_area = b1_wh[..., 0] * b1_wh[..., 1] b2_area = b2_wh[..., 0] * b2_wh[..., 1] iou = intersect_area / (b1_area + b2_area - intersect_area) return iou def yolo_loss(args, anchors, num_classes, ignore_thresh=.5, print_loss=False): '''Return yolo_loss tensor Parameters ---------- yolo_outputs: list of tensor, the output of yolo_body or tiny_yolo_body y_true: list of array, the output of preprocess_true_boxes anchors: array, shape=(N, 2), wh num_classes: integer ignore_thresh: float, the iou threshold whether to ignore object confidence loss Returns ------- loss: tensor, shape=(1,) ''' num_layers = len(anchors)//3 # default setting yolo_outputs = args[:num_layers] y_true = args[num_layers:] anchor_mask = [[6,7,8], [3,4,5], [0,1,2]] if num_layers==3 else [[3,4,5], [1,2,3]] input_shape = K.cast(K.shape(yolo_outputs[0])[1:3] * 32, K.dtype(y_true[0])) grid_shapes = [K.cast(K.shape(yolo_outputs[l])[1:3], K.dtype(y_true[0])) for l in range(num_layers)] loss = 0 m = K.shape(yolo_outputs[0])[0] # batch size, tensor mf = K.cast(m, K.dtype(yolo_outputs[0])) for l in range(num_layers): object_mask = y_true[l][..., 4:5] true_class_probs = y_true[l][..., 5:] grid, raw_pred, pred_xy, pred_wh = yolo_head(yolo_outputs[l], anchors[anchor_mask[l]], num_classes, input_shape, calc_loss=True) pred_box = K.concatenate([pred_xy, pred_wh]) # Darknet raw box to calculate loss. raw_true_xy = y_true[l][..., :2]*grid_shapes[l][::-1] - grid raw_true_wh = K.log(y_true[l][..., 2:4] / anchors[anchor_mask[l]] * input_shape[::-1]) raw_true_wh = K.switch(object_mask, raw_true_wh, K.zeros_like(raw_true_wh)) # avoid log(0)=-inf box_loss_scale = 2 - y_true[l][...,2:3]*y_true[l][...,3:4] # Find ignore mask, iterate over each of batch. ignore_mask = tf.TensorArray(K.dtype(y_true[0]), size=1, dynamic_size=True) object_mask_bool = K.cast(object_mask, 'bool') def loop_body(b, ignore_mask): true_box = tf.boolean_mask(y_true[l][b,...,0:4], object_mask_bool[b,...,0]) iou = box_iou(pred_box[b], true_box) best_iou = K.max(iou, axis=-1) ignore_mask = ignore_mask.write(b, K.cast(best_iou