yolov8.py

from tinygrad.nn import Conv2d, BatchNorm2d
from tinygrad.tensor import Tensor
import numpy as np
from itertools import chain
from pathlib import Path
import cv2
from collections import defaultdict
import time, sys
from tinygrad.helpers import fetch
from tinygrad.nn.state import safe_load, load_state_dict

#Model architecture from https://github.com/ultralytics/ultralytics/issues/189
#The upsampling class has been taken from this pull request https://github.com/tinygrad/tinygrad/pull/784 by dc-dc-dc. Now 2(?) models use upsampling. (retinet and this)

#Pre processing image functions.
def compute_transform(image, new_shape=(640, 640), auto=False, scaleFill=False, scaleup=True, stride=32):
  shape = image.shape[:2]  # current shape [height, width]
  new_shape = (new_shape, new_shape) if isinstance(new_shape, int) else new_shape
  r = min(new_shape[0] / shape[0], new_shape[1] / shape[1])
  r = min(r, 1.0) if not scaleup else r
  new_unpad = (int(round(shape[1] * r)), int(round(shape[0] * r)))
  dw, dh = new_shape[1] - new_unpad[0], new_shape[0] - new_unpad[1]
  dw, dh = (np.mod(dw, stride), np.mod(dh, stride)) if auto else (0.0, 0.0)
  new_unpad = (new_shape[1], new_shape[0]) if scaleFill else new_unpad
  dw /= 2
  dh /= 2
  image = cv2.resize(image, new_unpad, interpolation=cv2.INTER_LINEAR) if shape[::-1] != new_unpad else image
  top, bottom = int(round(dh - 0.1)), int(round(dh + 0.1))
  left, right = int(round(dw - 0.1)), int(round(dw + 0.1))
  image = cv2.copyMakeBorder(image, top, bottom, left, right, cv2.BORDER_CONSTANT, value=(114, 114, 114))
  return image

def preprocess(im, imgsz=640, model_stride=32, model_pt=True):
  same_shapes = all(x.shape == im[0].shape for x in im)
  auto = same_shapes and model_pt
  im = Tensor([compute_transform(x, new_shape=imgsz, auto=auto, stride=model_stride) for x in im])
  im = Tensor.stack(im) if im.shape[0] > 1 else im
  im = im[..., ::-1].permute(0, 3, 1, 2)  # BGR to RGB, BHWC to BCHW, (n, 3, h, w)
  im /= 255  # 0 - 255 to 0.0 - 1.0
  return im

# Post Processing functions
def box_area(box):
  return (box[:, 2] - box[:, 0]) * (box[:, 3] - box[:, 1])

def box_iou(box1, box2):
  lt = np.maximum(box1[:, None, :2], box2[:, :2])
  rb = np.minimum(box1[:, None, 2:], box2[:, 2:])
  wh = np.clip(rb - lt, 0, None)
  inter = wh[:, :, 0] * wh[:, :, 1]
  area1 = box_area(box1)[:, None]
  area2 = box_area(box2)[None, :]
  iou = inter / (area1 + area2 - inter)
  return iou

def compute_nms(boxes, scores, iou_threshold):
  order, keep = scores.argsort()[::-1], []
  while order.size > 0:
    i = order[0]
    keep.append(i)
    if order.size == 1:
      break
    iou = box_iou(boxes[i][None, :], boxes[order[1:]])
    inds = np.where(iou.squeeze() <= iou_threshold)[0]
    order = order[inds + 1]
  return np.array(keep)

def non_max_suppression(prediction, conf_thres=0.25, iou_thres=0.45, agnostic=False, max_det=300, nc=0, max_wh=7680):
  prediction = prediction[0] if isinstance(prediction, (list, tuple)) else prediction
  bs, nc = prediction.shape[0], nc or (prediction.shape[1] - 4)
  xc = np.amax(prediction[:, 4:4 + nc], axis=1) > conf_thres
  nm = prediction.shape[1] - nc - 4
  output = [np.zeros((0, 6 + nm))] * bs

  for xi, x in enumerate(prediction):
    x = x.swapaxes(0, -1)[xc[xi]]
    if not x.shape[0]: continue
    box, cls, mask = np.split(x, [4, 4 + nc], axis=1)
    conf, j = np.max(cls, axis=1, keepdims=True), np.argmax(cls, axis=1, keepdims=True)
    x = np.concatenate((xywh2xyxy(box), conf, j.astype(np.float32), mask), axis=1)
    x = x[conf.ravel() > conf_thres]
    if not x.shape[0]: continue
    x = x[np.argsort(-x[:, 4])]
    c = x[:, 5:6] * (0 if agnostic else max_wh)
    boxes, scores = x[:, :4] + c, x[:, 4]
    i = compute_nms(boxes, scores, iou_thres)[:max_det]
    output[xi] = x[i]
  return output

def postprocess(preds, img, orig_imgs):
  print('copying to CPU now for post processing')
  #if you are on CPU, this causes an overflow runtime error. doesn't "seem" to make any difference in the predictions though.
  # TODO: make non_max_suppression in tinygrad - to make this faster
  preds = preds.numpy() if isinstance(preds, Tensor) else preds
  preds = non_max_suppression(prediction=preds, conf_thres=0.25, iou_thres=0.7, agnostic=False, max_det=300)
  all_preds = []
  for i, pred in enumerate(preds):
    orig_img = orig_imgs[i] if isinstance(orig_imgs, list) else orig_imgs
    if not isinstance(orig_imgs, Tensor):
      pred[:, :4] = scale_boxes(img.shape[2:], pred[:, :4], orig_img.shape)
      all_preds.append(pred)
  return all_preds

def draw_bounding_boxes_and_save(orig_img_paths, output_img_paths, all_predictions, class_labels, iou_threshold=0.5):
  color_dict = {label: tuple((((i+1) * 50) % 256, ((i+1) * 100) % 256, ((i+1) * 150) % 256)) for i, label in enumerate(class_labels)}
  font = cv2.FONT_HERSHEY_SIMPLEX

  def is_bright_color(color):
    r, g, b = color
    brightness = (r * 299 + g * 587 + b * 114) / 1000
    return brightness > 127

  for img_idx, (orig_img_path, output_img_path, predictions) in enumerate(zip(orig_img_paths, output_img_paths, all_predictions)):
    predictions = np.array(predictions)
    orig_img = cv2.imread(orig_img_path) if not isinstance(orig_img_path, np.ndarray) else cv2.imdecode(orig_img_path, 1)
    height, width, _ = orig_img.shape
    box_thickness = int((height + width) / 400)
    font_scale = (height + width) / 2500

    grouped_preds = defaultdict(list)
    object_count = defaultdict(int)

    for pred_np in predictions:
      grouped_preds[int(pred_np[-1])].append(pred_np)

    def draw_box_and_label(pred, color):
      x1, y1, x2, y2, conf, _ = pred
      x1, y1, x2, y2 = map(int, (x1, y1, x2, y2))
      cv2.rectangle(orig_img, (x1, y1), (x2, y2), color, box_thickness)
      label = f"{class_labels[class_id]} {conf:.2f}"
      text_size, _ = cv2.getTextSize(label, font, font_scale, 1)
      label_y, bg_y = (y1 - 4, y1 - text_size[1] - 4) if y1 - text_size[1] - 4 > 0 else (y1 + text_size[1], y1)
      cv2.rectangle(orig_img, (x1, bg_y), (x1 + text_size[0], bg_y + text_size[1]), color, -1)
      font_color = (0, 0, 0) if is_bright_color(color) else (255, 255, 255)
      cv2.putText(orig_img, label, (x1, label_y), font, font_scale, font_color, 1, cv2.LINE_AA)

    for class_id, pred_list in grouped_preds.items():
      pred_list = np.array(pred_list)
      while len(pred_list) > 0:
        max_conf_idx = np.argmax(pred_list[:, 4])
        max_conf_pred = pred_list[max_conf_idx]
        pred_list = np.delete(pred_list, max_conf_idx, axis=0)
        color = color_dict[class_labels[class_id]]
        draw_box_and_label(max_conf_pred, color)
        object_count[class_labels[class_id]] += 1
        iou_scores = box_iou(np.array([max_conf_pred[:4]]), pred_list[:, :4])
        low_iou_indices = np.where(iou_scores[0] < iou_threshold)[0]
        pred_list = pred_list[low_iou_indices]
        for low_conf_pred in pred_list:
          draw_box_and_label(low_conf_pred, color)

    print(f"Image {img_idx + 1}:")
    print("Objects detected:")
    for obj, count in object_count.items():
      print(f"- {obj}: {count}")

    cv2.imwrite(output_img_path, orig_img)
    print(f'saved detections at {output_img_path}')

# utility functions for forward pass.
def dist2bbox(distance, anchor_points, xywh=True, dim=-1):
  lt, rb = distance.chunk(2, dim)
  x1y1 = anchor_points - lt
  x2y2 = anchor_points + rb
  if xywh:
    c_xy = (x1y1 + x2y2) / 2
    wh = x2y2 - x1y1
    return c_xy.cat(wh, dim=1)
  return x1y1.cat(x2y2, dim=1)

def make_anchors(feats, strides, grid_cell_offset=0.5):
  anchor_points, stride_tensor = [], []
  assert feats is not None
  for i, stride in enumerate(strides):
    _, _, h, w = feats[i].shape
    sx = Tensor.arange(w) + grid_cell_offset
    sy = Tensor.arange(h) + grid_cell_offset

    # this is np.meshgrid but in tinygrad
    sx = sx.reshape(1, -1).repeat([h, 1]).reshape(-1)
    sy = sy.reshape(-1, 1).repeat([1, w]).reshape(-1)

    anchor_points.append(Tensor.stack((sx, sy), -1).reshape(-1, 2))
    stride_tensor.append(Tensor.full((h * w), stride))
  anchor_points = anchor_points[0].cat(anchor_points[1], anchor_points[2])
  stride_tensor = stride_tensor[0].cat(stride_tensor[1], stride_tensor[2]).unsqueeze(1)
  return anchor_points, stride_tensor

# this function is from the original implementation
def autopad(k, p=None, d=1):  # kernel, padding, dilation
  if d > 1:
    k = d * (k - 1) + 1 if isinstance(k, int) else [d * (x - 1) + 1 for x in k]  # actual kernel-size
  if p is None:
    p = k // 2 if isinstance(k, int) else [x // 2 for x in k]  # auto-pad
  return p

def clip_boxes(boxes, shape):
  boxes[..., [0, 2]] = np.clip(boxes[..., [0, 2]], 0, shape[1])  # x1, x2
  boxes[..., [1, 3]] = np.clip(boxes[..., [1, 3]], 0, shape[0])  # y1, y2
  return boxes

def scale_boxes(img1_shape, boxes, img0_shape, ratio_pad=None):
  gain = ratio_pad if ratio_pad else min(img1_shape[0] / img0_shape[0], img1_shape[1] / img0_shape[1])
  pad = ((img1_shape[1] - img0_shape[1] * gain) / 2, (img1_shape[0] - img0_shape[0] * gain) / 2)
  boxes_np = boxes.numpy() if isinstance(boxes, Tensor) else boxes
  boxes_np[..., [0, 2]] -= pad[0]
  boxes_np[..., [1, 3]] -= pad[1]
  boxes_np[..., :4] /= gain
  boxes_np = clip_boxes(boxes_np, img0_shape)
  return boxes_np

def xywh2xyxy(x):
  xy = x[..., :2]  # center x, y
  wh = x[..., 2:4]  # width, height
  xy1 = xy - wh / 2  # top left x, y
  xy2 = xy + wh / 2  # bottom right x, y
  result = np.concatenate((xy1, xy2), axis=-1)
  return Tensor(result) if isinstance(x, Tensor) else result

def get_variant_multiples(variant):
  return {'n':(0.33, 0.25, 2.0), 's':(0.33, 0.50, 2.0), 'm':(0.67, 0.75, 1.5), 'l':(1.0, 1.0, 1.0), 'x':(1, 1.25, 1.0) }.get(variant, None)

def label_predictions(all_predictions):
  class_index_count = defaultdict(int)
  for predictions in all_predictions:
    predictions = np.array(predictions)
    for pred_np in predictions:
      class_id = int(pred_np[-1])
      class_index_count[class_id] += 1

  return dict(class_index_count)

#this is taken from https://github.com/tinygrad/tinygrad/pull/784/files by dc-dc-dc (Now 2 models use upsampling)
class Upsample:
  def __init__(self, scale_factor:int, mode: str = "nearest") -> None:
    assert mode == "nearest" # only mode supported for now
    self.mode = mode
    self.scale_factor = scale_factor

  def __call__(self, x: Tensor) -> Tensor:
    assert len(x.shape) > 2 and len(x.shape) <= 5
    (b, c), _lens = x.shape[:2], len(x.shape[2:])
    tmp = x.reshape([b, c, -1] + [1] * _lens) * Tensor.ones(*[1, 1, 1] + [self.scale_factor] * _lens)
    return tmp.reshape(list(x.shape) + [self.scale_factor] * _lens).permute([0, 1] + list(chain.from_iterable([[y+2, y+2+_lens] for y in range(_lens)]))).reshape([b, c] + [x * self.scale_factor for x in x.shape[2:]])

class Conv_Block:
  def __init__(self, c1, c2, kernel_size=1, stride=1, groups=1, dilation=1, padding=None):
    self.conv = Conv2d(c1,c2, kernel_size, stride, padding=autopad(kernel_size, padding, dilation), bias=False, groups=groups, dilation=dilation)
    self.bn = BatchNorm2d(c2, eps=0.001)

  def __call__(self, x):
    return self.bn(self.conv(x)).silu()

class Bottleneck:
  def __init__(self, c1, c2 , shortcut: bool, g=1, kernels: list = (3,3), channel_factor=0.5):
    c_ = int(c2 * channel_factor)
    self.cv1 = Conv_Block(c1, c_, kernel_size=kernels[0], stride=1, padding=None)
    self.cv2 = Conv_Block(c_, c2, kernel_size=kernels[1], stride=1, padding=None, groups=g)
    self.residual = c1 == c2 and shortcut

  def __call__(self, x):
    return x + self.cv2(self.cv1(x)) if self.residual else self.cv2(self.cv1(x))

class C2f:
  def __init__(self, c1, c2, n=1, shortcut=False, g=1, e=0.5):
    self.c = int(c2 * e)
    self.cv1 = Conv_Block(c1, 2 * self.c, 1,)
    self.cv2 = Conv_Block((2 + n) * self.c, c2, 1)
    self.bottleneck = [Bottleneck(self.c, self.c, shortcut, g, kernels=[(3, 3), (3, 3)], channel_factor=1.0) for _ in range(n)]

  def __call__(self, x):
    y= list(self.cv1(x).chunk(2, 1))
    y.extend(m(y[-1]) for m in self.bottleneck)
    z = y[0]
    for i in y[1:]: z = z.cat(i, dim=1)
    return self.cv2(z)

class SPPF:
  def __init__(self, c1, c2, k=5):
    c_ = c1 // 2  # hidden channels
    self.cv1 = Conv_Block(c1, c_, 1, 1, padding=None)
    self.cv2 = Conv_Block(c_ * 4, c2, 1, 1, padding=None)

    # TODO: this pads with 0s, whereas torch function pads with -infinity. This results in a < 2% difference in prediction which does not make a difference visually.
    self.maxpool = lambda x : x.pad2d((k // 2, k // 2, k // 2, k // 2)).max_pool2d(kernel_size=k, stride=1)

  def __call__(self, x):
    x = self.cv1(x)
    x2 = self.maxpool(x)
    x3 = self.maxpool(x2)
    x4 = self.maxpool(x3)
    return self.cv2(x.cat(x2, x3, x4, dim=1))

class DFL:
  def __init__(self, c1=16):
    self.conv = Conv2d(c1, 1, 1, bias=False)
    x = Tensor.arange(c1)
    self.conv.weight.replace(x.reshape(1, c1, 1, 1))
    self.c1 = c1

  def __call__(self, x):
    b, c, a = x.shape # batch, channels, anchors
    return self.conv(x.reshape(b, 4, self.c1, a).transpose(2, 1).softmax(1)).reshape(b, 4, a)

#backbone
class Darknet:
  def __init__(self, w, r, d):
    self.b1 = [Conv_Block(c1=3, c2= int(64*w), kernel_size=3, stride=2, padding=1), Conv_Block(int(64*w), int(128*w), kernel_size=3, stride=2, padding=1)]
    self.b2 = [C2f(c1=int(128*w), c2=int(128*w), n=round(3*d), shortcut=True), Conv_Block(int(128*w), int(256*w), 3, 2, 1), C2f(int(256*w), int(256*w), round(6*d), True)]
    self.b3 = [Conv_Block(int(256*w), int(512*w), kernel_size=3, stride=2, padding=1), C2f(int(512*w), int(512*w), round(6*d), True)]
    self.b4 = [Conv_Block(int(512*w), int(512*w*r), kernel_size=3, stride=2, padding=1), C2f(int(512*w*r), int(512*w*r), round(3*d), True)]
    self.b5 = [SPPF(int(512*w*r), int(512*w*r), 5)]

  def return_modules(self):
    return [*self.b1, *self.b2, *self.b3, *self.b4, *self.b5]

  def __call__(self, x):
    x1 = x.sequential(self.b1)
    x2 = x1.sequential(self.b2)
    x3 = x2.sequential(self.b3)
    x4 = x3.sequential(self.b4)
    x5 = x4.sequential(self.b5)
    return (x2, x3, x5)

#yolo fpn (neck)
class Yolov8NECK:
  def __init__(self, w, r, d):  #width_multiple, ratio_multiple, depth_multiple
    self.up = Upsample(2, mode='nearest')
    self.n1 = C2f(c1=int(512*w*(1+r)), c2=int(512*w), n=round(3*d), shortcut=False)
    self.n2 = C2f(c1=int(768*w), c2=int(256*w), n=round(3*d), shortcut=False)
    self.n3 = Conv_Block(c1=int(256*w), c2=int(256*w), kernel_size=3, stride=2, padding=1)
    self.n4 = C2f(c1=int(768*w), c2=int(512*w), n=round(3*d), shortcut=False)
    self.n5 = Conv_Block(c1=int(512* w), c2=int(512 * w), kernel_size=3, stride=2, padding=1)
    self.n6 = C2f(c1=int(512*w*(1+r)), c2=int(512*w*r), n=round(3*d), shortcut=False)

  def return_modules(self):
    return [self.n1, self.n2, self.n3, self.n4, self.n5, self.n6]

  def __call__(self, p3, p4, p5):
    x = self.n1(self.up(p5).cat(p4, dim=1))
    head_1 = self.n2(self.up(x).cat(p3, dim=1))
    head_2 = self.n4(self.n3(head_1).cat(x, dim=1))
    head_3 = self.n6(self.n5(head_2).cat(p5, dim=1))
    return [head_1, head_2, head_3]

#task specific head.
class DetectionHead:
  def __init__(self, nc=80, filters=()):
    self.ch = 16
    self.nc = nc  # number of classes
    self.nl = len(filters)
    self.no = nc + self.ch * 4  #
    self.stride = [8, 16, 32]
    c1 = max(filters[0], self.nc)
    c2 = max((filters[0] // 4, self.ch * 4))
    self.dfl = DFL(self.ch)
    self.cv3 = [[Conv_Block(x, c1, 3), Conv_Block(c1, c1, 3), Conv2d(c1, self.nc, 1)] for x in filters]
    self.cv2 = [[Conv_Block(x, c2, 3), Conv_Block(c2, c2, 3), Conv2d(c2, 4 * self.ch, 1)] for x in filters]

  def __call__(self, x):
    for i in range(self.nl):
      x[i] = (x[i].sequential(self.cv2[i]).cat(x[i].sequential(self.cv3[i]), dim=1))
    self.anchors, self.strides = (x.transpose(0, 1) for x in make_anchors(x, self.stride, 0.5))
    y = [(i.reshape(x[0].shape[0], self.no, -1)) for i in x]
    x_cat = y[0].cat(y[1], y[2], dim=2)
    box, cls = x_cat[:, :self.ch * 4], x_cat[:, self.ch * 4:]
    dbox = dist2bbox(self.dfl(box), self.anchors.unsqueeze(0), xywh=True, dim=1) * self.strides
    z = dbox.cat(cls.sigmoid(), dim=1)
    return z

class YOLOv8:
  def __init__(self, w, r,  d, num_classes): #width_multiple, ratio_multiple, depth_multiple
    self.net = Darknet(w, r, d)
    self.fpn = Yolov8NECK(w, r, d)
    self.head = DetectionHead(num_classes, filters=(int(256*w), int(512*w), int(512*w*r)))

  def __call__(self, x):
    x = self.net(x)
    x = self.fpn(*x)
    return self.head(x)

  def return_all_trainable_modules(self):
    backbone_modules = [*range(10)]
    yolov8neck_modules = [12, 15, 16, 18, 19, 21]
    yolov8_head_weights = [(22, self.head)]
    return [*zip(backbone_modules, self.net.return_modules()), *zip(yolov8neck_modules, self.fpn.return_modules()), *yolov8_head_weights]

if __name__ == '__main__':

  # usage : python3 yolov8.py "image_URL OR image_path" "v8 variant" (optional, n is default)
  if len(sys.argv) < 2:
    print("Error: Image URL or path not provided.")
    sys.exit(1)

  img_path = sys.argv[1]
  yolo_variant = sys.argv[2] if len(sys.argv) >= 3 else (print("No variant given, so choosing 'n' as the default. Yolov8 has different variants, you can choose from ['n', 's', 'm', 'l', 'x']") or 'n')
  print(f'running inference for YOLO version {yolo_variant}')

  output_folder_path = Path('./outputs_yolov8')
  output_folder_path.mkdir(parents=True, exist_ok=True)
  #absolute image path or URL
  image_location = [np.frombuffer(fetch(img_path).read_bytes(), np.uint8)]
  image = [cv2.imdecode(image_location[0], 1)]
  out_paths = [(output_folder_path / f"{Path(img_path).stem}_output{Path(img_path).suffix or '.png'}").as_posix()]
  if not isinstance(image[0], np.ndarray):
    print('Error in image loading. Check your image file.')
    sys.exit(1)
  pre_processed_image = preprocess(image)

  # Different YOLOv8 variants use different w , r, and d multiples. For a list , refer to this yaml file (the scales section) https://github.com/ultralytics/ultralytics/blob/main/ultralytics/models/v8/yolov8.yaml
  depth, width, ratio = get_variant_multiples(yolo_variant)
  yolo_infer = YOLOv8(w=width, r=ratio, d=depth, num_classes=80)

  state_dict = safe_load(fetch(f'https://gitlab.com/r3sist/yolov8_weights/-/raw/master/yolov8{yolo_variant}.safetensors'))
  load_state_dict(yolo_infer, state_dict)

  st = time.time()
  predictions = yolo_infer(pre_processed_image)
  print(f'did inference in {int(round(((time.time() - st) * 1000)))}ms')

  post_predictions = postprocess(preds=predictions, img=pre_processed_image, orig_imgs=image)

  #v8 and v3 have same 80 class names for Object Detection
  class_labels = fetch('https://raw.githubusercontent.com/pjreddie/darknet/master/data/coco.names').read_text().split("\n")

  draw_bounding_boxes_and_save(orig_img_paths=image_location, output_img_paths=out_paths, all_predictions=post_predictions, class_labels=class_labels)

# TODO for later:
#  1. Fix SPPF minor difference due to maxpool
#  2. AST exp overflow warning while on cpu
#  3. Make NMS faster
#  4. Add video inference and webcam support