昇思训练营打卡第十一天（FCN图像语义分割）

这一部分主要对训练出来的模型效果进行评估，为了便于解释，假设如下：共有 𝑘+1𝑘+1 个类（从 𝐿0𝐿0 到 𝐿𝑘𝐿𝑘, 其中包含一个空类或背景）， 𝑝𝑖𝑗𝑝𝑖𝑗 表示本属于𝑖𝑖类但被预测为𝑗𝑗类的像素数量。即, 𝑝𝑖𝑖𝑝𝑖𝑖 表示真正的数量, 而 𝑝𝑖𝑗𝑝𝑗𝑖𝑝𝑖𝑗𝑝𝑗𝑖 则分别被解释为假正和假负, 尽管两者都是假正与假负之

qhcl246810

301人浏览 · 2024-06-30 00:54:26

qhcl246810 · 2024-06-30 00:54:26 发布

什么是FCN模型？

因为模型网络中所有的层都是卷积层，故称为全卷积网络。

全卷积神经网络主要使用了三种技术：

卷积化（Convolutional）
上采样（Upsample）
跳跃结构（Skip Layer）

网络特点

不含全连接层(fc)的全卷积(fully conv)网络，可适应任意尺寸输入。
增大数据尺寸的反卷积(deconv)层，能够输出精细的结果。
结合不同深度层结果的跳级(skip)结构，同时确保鲁棒性和精确性。

数据处理

数据预处理

由于PASCAL VOC 2012数据集中图像的分辨率大多不一致，无法放在一个tensor中，故输入前需做标准化处理。

数据加载¶

将PASCAL VOC 2012数据集与SDB数据集进行混合。

import numpy as np
import cv2
import mindspore.dataset as ds

class SegDataset:
    def __init__(self,
                 image_mean,
                 image_std,
                 data_file='',
                 batch_size=32,
                 crop_size=512,
                 max_scale=2.0,
                 min_scale=0.5,
                 ignore_label=255,
                 num_classes=21,
                 num_readers=2,
                 num_parallel_calls=4):

        self.data_file = data_file
        self.batch_size = batch_size
        self.crop_size = crop_size
        self.image_mean = np.array(image_mean, dtype=np.float32)
        self.image_std = np.array(image_std, dtype=np.float32)
        self.max_scale = max_scale
        self.min_scale = min_scale
        self.ignore_label = ignore_label
        self.num_classes = num_classes
        self.num_readers = num_readers
        self.num_parallel_calls = num_parallel_calls
        max_scale > min_scale

    def preprocess_dataset(self, image, label):
        image_out = cv2.imdecode(np.frombuffer(image, dtype=np.uint8), cv2.IMREAD_COLOR)
        label_out = cv2.imdecode(np.frombuffer(label, dtype=np.uint8), cv2.IMREAD_GRAYSCALE)
        sc = np.random.uniform(self.min_scale, self.max_scale)
        new_h, new_w = int(sc * image_out.shape[0]), int(sc * image_out.shape[1])
        image_out = cv2.resize(image_out, (new_w, new_h), interpolation=cv2.INTER_CUBIC)
        label_out = cv2.resize(label_out, (new_w, new_h), interpolation=cv2.INTER_NEAREST)

        image_out = (image_out - self.image_mean) / self.image_std
        out_h, out_w = max(new_h, self.crop_size), max(new_w, self.crop_size)
        pad_h, pad_w = out_h - new_h, out_w - new_w
        if pad_h > 0 or pad_w > 0:
            image_out = cv2.copyMakeBorder(image_out, 0, pad_h, 0, pad_w, cv2.BORDER_CONSTANT, value=0)
            label_out = cv2.copyMakeBorder(label_out, 0, pad_h, 0, pad_w, cv2.BORDER_CONSTANT, value=self.ignore_label)
        offset_h = np.random.randint(0, out_h - self.crop_size + 1)
        offset_w = np.random.randint(0, out_w - self.crop_size + 1)
        image_out = image_out[offset_h: offset_h + self.crop_size, offset_w: offset_w + self.crop_size, :]
        label_out = label_out[offset_h: offset_h + self.crop_size, offset_w: offset_w+self.crop_size]
        if np.random.uniform(0.0, 1.0) > 0.5:
            image_out = image_out[:, ::-1, :]
            label_out = label_out[:, ::-1]
        image_out = image_out.transpose((2, 0, 1))
        image_out = image_out.copy()
        label_out = label_out.copy()
        label_out = label_out.astype("int32")
        return image_out, label_out

    def get_dataset(self):
        ds.config.set_numa_enable(True)
        dataset = ds.MindDataset(self.data_file, columns_list=["data", "label"],
                                 shuffle=True, num_parallel_workers=self.num_readers)
        transforms_list = self.preprocess_dataset
        dataset = dataset.map(operations=transforms_list, input_columns=["data", "label"],
                              output_columns=["data", "label"],
                              num_parallel_workers=self.num_parallel_calls)
        dataset = dataset.shuffle(buffer_size=self.batch_size * 10)
        dataset = dataset.batch(self.batch_size, drop_remainder=True)
        return dataset


# 定义创建数据集的参数
IMAGE_MEAN = [103.53, 116.28, 123.675]
IMAGE_STD = [57.375, 57.120, 58.395]
DATA_FILE = "dataset/dataset_fcn8s/mindname.mindrecord"

# 定义模型训练参数
train_batch_size = 4
crop_size = 512
min_scale = 0.5
max_scale = 2.0
ignore_label = 255
num_classes = 21

# 实例化Dataset
dataset = SegDataset(image_mean=IMAGE_MEAN,
                     image_std=IMAGE_STD,
                     data_file=DATA_FILE,
                     batch_size=train_batch_size,
                     crop_size=crop_size,
                     max_scale=max_scale,
                     min_scale=min_scale,
                     ignore_label=ignore_label,
                     num_classes=num_classes,
                     num_readers=2,
                     num_parallel_calls=4)

dataset = dataset.get_dataset()

训练集可视化

运行以下代码观察载入的数据集图片（数据处理过程中已做归一化处理）。

import numpy as np
import matplotlib.pyplot as plt

plt.figure(figsize=(16, 8))

# 对训练集中的数据进行展示
for i in range(1, 9):
    plt.subplot(2, 4, i)
    show_data = next(dataset.create_dict_iterator())
    show_images = show_data["data"].asnumpy()
    show_images = np.clip(show_images, 0, 1)
# 将图片转换HWC格式后进行展示
    plt.imshow(show_images[0].transpose(1, 2, 0))
    plt.axis("off")
    plt.subplots_adjust(wspace=0.05, hspace=0)
plt.show()

网络构建

网络流程

FCN网络的流程如下图所示：

输入图像image，经过pool1池化后，尺寸变为原始尺寸的1/2。
经过pool2池化，尺寸变为原始尺寸的1/4。
接着经过pool3、pool4、pool5池化，大小分别变为原始尺寸的1/8、1/16、1/32。
经过conv6-7卷积，输出的尺寸依然是原图的1/32。
FCN-32s是最后使用反卷积，使得输出图像大小与输入图像相同。
FCN-16s是将conv7的输出进行反卷积，使其尺寸扩大两倍至原图的1/16，并将其与pool4输出的特征图进行融合，后通过反卷积扩大到原始尺寸。
FCN-8s是将conv7的输出进行反卷积扩大4倍，将pool4输出的特征图反卷积扩大2倍，并将pool3输出特征图拿出，三者融合后通反卷积扩大到原始尺寸。

import mindspore.nn as nn

class FCN8s(nn.Cell):
    def __init__(self, n_class):
        super().__init__()
        self.n_class = n_class
        self.conv1 = nn.SequentialCell(
            nn.Conv2d(in_channels=3, out_channels=64,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(64),
            nn.ReLU(),
            nn.Conv2d(in_channels=64, out_channels=64,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(64),
            nn.ReLU()
        )
        self.pool1 = nn.MaxPool2d(kernel_size=2, stride=2)
        self.conv2 = nn.SequentialCell(
            nn.Conv2d(in_channels=64, out_channels=128,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(128),
            nn.ReLU(),
            nn.Conv2d(in_channels=128, out_channels=128,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(128),
            nn.ReLU()
        )
        self.pool2 = nn.MaxPool2d(kernel_size=2, stride=2)
        self.conv3 = nn.SequentialCell(
            nn.Conv2d(in_channels=128, out_channels=256,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(256),
            nn.ReLU(),
            nn.Conv2d(in_channels=256, out_channels=256,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(256),
            nn.ReLU(),
            nn.Conv2d(in_channels=256, out_channels=256,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(256),
            nn.ReLU()
        )
        self.pool3 = nn.MaxPool2d(kernel_size=2, stride=2)
        self.conv4 = nn.SequentialCell(
            nn.Conv2d(in_channels=256, out_channels=512,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(512),
            nn.ReLU(),
            nn.Conv2d(in_channels=512, out_channels=512,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(512),
            nn.ReLU(),
            nn.Conv2d(in_channels=512, out_channels=512,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(512),
            nn.ReLU()
        )
        self.pool4 = nn.MaxPool2d(kernel_size=2, stride=2)
        self.conv5 = nn.SequentialCell(
            nn.Conv2d(in_channels=512, out_channels=512,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(512),
            nn.ReLU(),
            nn.Conv2d(in_channels=512, out_channels=512,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(512),
            nn.ReLU(),
            nn.Conv2d(in_channels=512, out_channels=512,
                      kernel_size=3, weight_init='xavier_uniform'),
            nn.BatchNorm2d(512),
            nn.ReLU()
        )
        self.pool5 = nn.MaxPool2d(kernel_size=2, stride=2)
        self.conv6 = nn.SequentialCell(
            nn.Conv2d(in_channels=512, out_channels=4096,
                      kernel_size=7, weight_init='xavier_uniform'),
            nn.BatchNorm2d(4096),
            nn.ReLU(),
        )
        self.conv7 = nn.SequentialCell(
            nn.Conv2d(in_channels=4096, out_channels=4096,
                      kernel_size=1, weight_init='xavier_uniform'),
            nn.BatchNorm2d(4096),
            nn.ReLU(),
        )
        self.score_fr = nn.Conv2d(in_channels=4096, out_channels=self.n_class,
                                  kernel_size=1, weight_init='xavier_uniform')
        self.upscore2 = nn.Conv2dTranspose(in_channels=self.n_class, out_channels=self.n_class,
                                           kernel_size=4, stride=2, weight_init='xavier_uniform')
        self.score_pool4 = nn.Conv2d(in_channels=512, out_channels=self.n_class,
                                     kernel_size=1, weight_init='xavier_uniform')
        self.upscore_pool4 = nn.Conv2dTranspose(in_channels=self.n_class, out_channels=self.n_class,
                                                kernel_size=4, stride=2, weight_init='xavier_uniform')
        self.score_pool3 = nn.Conv2d(in_channels=256, out_channels=self.n_class,
                                     kernel_size=1, weight_init='xavier_uniform')
        self.upscore8 = nn.Conv2dTranspose(in_channels=self.n_class, out_channels=self.n_class,
                                           kernel_size=16, stride=8, weight_init='xavier_uniform')

    def construct(self, x):
        x1 = self.conv1(x)
        p1 = self.pool1(x1)
        x2 = self.conv2(p1)
        p2 = self.pool2(x2)
        x3 = self.conv3(p2)
        p3 = self.pool3(x3)
        x4 = self.conv4(p3)
        p4 = self.pool4(x4)
        x5 = self.conv5(p4)
        p5 = self.pool5(x5)
        x6 = self.conv6(p5)
        x7 = self.conv7(x6)
        sf = self.score_fr(x7)
        u2 = self.upscore2(sf)
        s4 = self.score_pool4(p4)
        f4 = s4 + u2
        u4 = self.upscore_pool4(f4)
        s3 = self.score_pool3(p3)
        f3 = s3 + u4
        out = self.upscore8(f3)
        return out

训练准备

导入VGG-16部分预训练权重

FCN使用VGG-16作为骨干网络，用于实现图像编码。使用下面代码导入VGG-16预训练模型的部分预训练权重。

from download import download
from mindspore import load_checkpoint, load_param_into_net

url = "https://mindspore-website.obs.cn-north-4.myhuaweicloud.com/notebook/datasets/fcn8s_vgg16_pretrain.ckpt"
download(url, "fcn8s_vgg16_pretrain.ckpt", replace=True)
def load_vgg16():
    ckpt_vgg16 = "fcn8s_vgg16_pretrain.ckpt"
    param_vgg = load_checkpoint(ckpt_vgg16)
    load_param_into_net(net, param_vgg)

自定义评价指标 Metrics

import numpy as np
import mindspore as ms
import mindspore.nn as nn
import mindspore.train as train

class PixelAccuracy(train.Metric):
    def __init__(self, num_class=21):
        super(PixelAccuracy, self).__init__()
        self.num_class = num_class

    def _generate_matrix(self, gt_image, pre_image):
        mask = (gt_image >= 0) & (gt_image < self.num_class)
        label = self.num_class * gt_image[mask].astype('int') + pre_image[mask]
        count = np.bincount(label, minlength=self.num_class**2)
        confusion_matrix = count.reshape(self.num_class, self.num_class)
        return confusion_matrix

    def clear(self):
        self.confusion_matrix = np.zeros((self.num_class,) * 2)

    def update(self, *inputs):
        y_pred = inputs[0].asnumpy().argmax(axis=1)
        y = inputs[1].asnumpy().reshape(4, 512, 512)
        self.confusion_matrix += self._generate_matrix(y, y_pred)

    def eval(self):
        pixel_accuracy = np.diag(self.confusion_matrix).sum() / self.confusion_matrix.sum()
        return pixel_accuracy


class PixelAccuracyClass(train.Metric):
    def __init__(self, num_class=21):
        super(PixelAccuracyClass, self).__init__()
        self.num_class = num_class

    def _generate_matrix(self, gt_image, pre_image):
        mask = (gt_image >= 0) & (gt_image < self.num_class)
        label = self.num_class * gt_image[mask].astype('int') + pre_image[mask]
        count = np.bincount(label, minlength=self.num_class**2)
        confusion_matrix = count.reshape(self.num_class, self.num_class)
        return confusion_matrix

    def update(self, *inputs):
        y_pred = inputs[0].asnumpy().argmax(axis=1)
        y = inputs[1].asnumpy().reshape(4, 512, 512)
        self.confusion_matrix += self._generate_matrix(y, y_pred)

    def clear(self):
        self.confusion_matrix = np.zeros((self.num_class,) * 2)

    def eval(self):
        mean_pixel_accuracy = np.diag(self.confusion_matrix) / self.confusion_matrix.sum(axis=1)
        mean_pixel_accuracy = np.nanmean(mean_pixel_accuracy)
        return mean_pixel_accuracy


class MeanIntersectionOverUnion(train.Metric):
    def __init__(self, num_class=21):
        super(MeanIntersectionOverUnion, self).__init__()
        self.num_class = num_class

    def _generate_matrix(self, gt_image, pre_image):
        mask = (gt_image >= 0) & (gt_image < self.num_class)
        label = self.num_class * gt_image[mask].astype('int') + pre_image[mask]
        count = np.bincount(label, minlength=self.num_class**2)
        confusion_matrix = count.reshape(self.num_class, self.num_class)
        return confusion_matrix

    def update(self, *inputs):
        y_pred = inputs[0].asnumpy().argmax(axis=1)
        y = inputs[1].asnumpy().reshape(4, 512, 512)
        self.confusion_matrix += self._generate_matrix(y, y_pred)

    def clear(self):
        self.confusion_matrix = np.zeros((self.num_class,) * 2)

    def eval(self):
        mean_iou = np.diag(self.confusion_matrix) / (
            np.sum(self.confusion_matrix, axis=1) + np.sum(self.confusion_matrix, axis=0) -
            np.diag(self.confusion_matrix))
        mean_iou = np.nanmean(mean_iou)
        return mean_iou


class FrequencyWeightedIntersectionOverUnion(train.Metric):
    def __init__(self, num_class=21):
        super(FrequencyWeightedIntersectionOverUnion, self).__init__()
        self.num_class = num_class

    def _generate_matrix(self, gt_image, pre_image):
        mask = (gt_image >= 0) & (gt_image < self.num_class)
        label = self.num_class * gt_image[mask].astype('int') + pre_image[mask]
        count = np.bincount(label, minlength=self.num_class**2)
        confusion_matrix = count.reshape(self.num_class, self.num_class)
        return confusion_matrix

    def update(self, *inputs):
        y_pred = inputs[0].asnumpy().argmax(axis=1)
        y = inputs[1].asnumpy().reshape(4, 512, 512)
        self.confusion_matrix += self._generate_matrix(y, y_pred)

    def clear(self):
        self.confusion_matrix = np.zeros((self.num_class,) * 2)

    def eval(self):
        freq = np.sum(self.confusion_matrix, axis=1) / np.sum(self.confusion_matrix)
        iu = np.diag(self.confusion_matrix) / (
            np.sum(self.confusion_matrix, axis=1) + np.sum(self.confusion_matrix, axis=0) -
            np.diag(self.confusion_matrix))

        frequency_weighted_iou = (freq[freq > 0] * iu[freq > 0]).sum()
        return frequency_weighted_iou

模型训练

导入VGG-16预训练参数后，实例化损失函数、优化器，使用Model接口编译网络，训练FCN-8s网络。

import mindspore
from mindspore import Tensor
import mindspore.nn as nn
from mindspore.train import ModelCheckpoint, CheckpointConfig, LossMonitor, TimeMonitor, Model

device_target = "Ascend"
mindspore.set_context(mode=mindspore.PYNATIVE_MODE, device_target=device_target)

train_batch_size = 4
num_classes = 21
# 初始化模型结构
net = FCN8s(n_class=21)
# 导入vgg16预训练参数
load_vgg16()
# 计算学习率
min_lr = 0.0005
base_lr = 0.05
train_epochs = 1
iters_per_epoch = dataset.get_dataset_size()
total_step = iters_per_epoch * train_epochs

lr_scheduler = mindspore.nn.cosine_decay_lr(min_lr,
                                            base_lr,
                                            total_step,
                                            iters_per_epoch,
                                            decay_epoch=2)
lr = Tensor(lr_scheduler[-1])

# 定义损失函数
loss = nn.CrossEntropyLoss(ignore_index=255)
# 定义优化器
optimizer = nn.Momentum(params=net.trainable_params(), learning_rate=lr, momentum=0.9, weight_decay=0.0001)
# 定义loss_scale
scale_factor = 4
scale_window = 3000
loss_scale_manager = ms.amp.DynamicLossScaleManager(scale_factor, scale_window)
# 初始化模型
if device_target == "Ascend":
    model = Model(net, loss_fn=loss, optimizer=optimizer, loss_scale_manager=loss_scale_manager, metrics={"pixel accuracy": PixelAccuracy(), "mean pixel accuracy": PixelAccuracyClass(), "mean IoU": MeanIntersectionOverUnion(), "frequency weighted IoU": FrequencyWeightedIntersectionOverUnion()})
else:
    model = Model(net, loss_fn=loss, optimizer=optimizer, metrics={"pixel accuracy": PixelAccuracy(), "mean pixel accuracy": PixelAccuracyClass(), "mean IoU": MeanIntersectionOverUnion(), "frequency weighted IoU": FrequencyWeightedIntersectionOverUnion()})

# 设置ckpt文件保存的参数
time_callback = TimeMonitor(data_size=iters_per_epoch)
loss_callback = LossMonitor()
callbacks = [time_callback, loss_callback]
save_steps = 330
keep_checkpoint_max = 5
config_ckpt = CheckpointConfig(save_checkpoint_steps=10,
                               keep_checkpoint_max=keep_checkpoint_max)
ckpt_callback = ModelCheckpoint(prefix="FCN8s",
                                directory="./ckpt",
                                config=config_ckpt)
callbacks.append(ckpt_callback)
model.train(train_epochs, dataset, callbacks=callbacks)

模型评估

IMAGE_MEAN = [103.53, 116.28, 123.675]
IMAGE_STD = [57.375, 57.120, 58.395]
DATA_FILE = "dataset/dataset_fcn8s/mindname.mindrecord"

# 下载已训练好的权重文件
url = "https://mindspore-website.obs.cn-north-4.myhuaweicloud.com/notebook/datasets/FCN8s.ckpt"
download(url, "FCN8s.ckpt", replace=True)
net = FCN8s(n_class=num_classes)

ckpt_file = "FCN8s.ckpt"
param_dict = load_checkpoint(ckpt_file)
load_param_into_net(net, param_dict)

if device_target == "Ascend":
    model = Model(net, loss_fn=loss, optimizer=optimizer, loss_scale_manager=loss_scale_manager, metrics={"pixel accuracy": PixelAccuracy(), "mean pixel accuracy": PixelAccuracyClass(), "mean IoU": MeanIntersectionOverUnion(), "frequency weighted IoU": FrequencyWeightedIntersectionOverUnion()})
else:
    model = Model(net, loss_fn=loss, optimizer=optimizer, metrics={"pixel accuracy": PixelAccuracy(), "mean pixel accuracy": PixelAccuracyClass(), "mean IoU": MeanIntersectionOverUnion(), "frequency weighted IoU": FrequencyWeightedIntersectionOverUnion()})

# 实例化Dataset
dataset = SegDataset(image_mean=IMAGE_MEAN,
                     image_std=IMAGE_STD,
                     data_file=DATA_FILE,
                     batch_size=train_batch_size,
                     crop_size=crop_size,
                     max_scale=max_scale,
                     min_scale=min_scale,
                     ignore_label=ignore_label,
                     num_classes=num_classes,
                     num_readers=2,
                     num_parallel_calls=4)
dataset_eval = dataset.get_dataset()
model.eval(dataset_eval)

模型推理

使用训练的网络对模型推理结果进行展示。

import cv2
import matplotlib.pyplot as plt

net = FCN8s(n_class=num_classes)
# 设置超参
ckpt_file = "FCN8s.ckpt"
param_dict = load_checkpoint(ckpt_file)
load_param_into_net(net, param_dict)
eval_batch_size = 4
img_lst = []
mask_lst = []
res_lst = []
# 推理效果展示(上方为输入图片，下方为推理效果图片)
plt.figure(figsize=(8, 5))
show_data = next(dataset_eval.create_dict_iterator())
show_images = show_data["data"].asnumpy()
mask_images = show_data["label"].reshape([4, 512, 512])
show_images = np.clip(show_images, 0, 1)
for i in range(eval_batch_size):
    img_lst.append(show_images[i])
    mask_lst.append(mask_images[i])
res = net(show_data["data"]).asnumpy().argmax(axis=1)
for i in range(eval_batch_size):
    plt.subplot(2, 4, i + 1)
    plt.imshow(img_lst[i].transpose(1, 2, 0))
    plt.axis("off")
    plt.subplots_adjust(wspace=0.05, hspace=0.02)
    plt.subplot(2, 4, i + 5)
    plt.imshow(res[i])
    plt.axis("off")
    plt.subplots_adjust(wspace=0.05, hspace=0.02)
plt.show()