基于深度卷积神经网络（CNN）模型的图像着色研究与应用系统实现

1.摘要

许多历史照片都是黑白的，通过颜色化可以恢复这些照片的历史感和真实感，使人们更好地理解和感受历史事件。随着深度学习技术的发展，特别是卷积神经网络和自监督学习的兴起，研究人员提出了新的方法来解决这些问题。通过将颜色化问题表述为分类任务，并使用大规模数据集进行训练，开发一种完全自动的、生成逼真彩色图像的方法。本文将深度卷积神经网络（CNN）设计实现一个复杂结构的生成模型，旨在通过多阶段的编码器-解码器结构，能够有效地将灰度图像转换为彩色图像。最后，本文将实现一个简单的Web应用，用户可以通过上传灰度图像，应用会使用预训练的Caffe模型对其进行颜色化，并将结果返回给用户。

2.模型设计

        model1=[nn.Conv2d(1, 64, kernel_size=3, stride=1, padding=1, bias=True),]
        model1+=[nn.ReLU(True),]
        model1+=[nn.Conv2d(64, 64, kernel_size=3, stride=2, padding=1, bias=True),]
        model1+=[nn.ReLU(True),]
        model1+=[norm_layer(64),]

        model2=[nn.Conv2d(64, 128, kernel_size=3, stride=1, padding=1, bias=True),]
        model2+=[nn.ReLU(True),]
        model2+=[nn.Conv2d(128, 128, kernel_size=3, stride=2, padding=1, bias=True),]
        model2+=[nn.ReLU(True),]
        model2+=[norm_layer(128),]

        model3=[nn.Conv2d(128, 256, kernel_size=3, stride=1, padding=1, bias=True),]
        model3+=[nn.ReLU(True),]
        model3+=[nn.Conv2d(256, 256, kernel_size=3, stride=1, padding=1, bias=True),]
        model3+=[nn.ReLU(True),]
        model3+=[nn.Conv2d(256, 256, kernel_size=3, stride=2, padding=1, bias=True),]
        model3+=[nn.ReLU(True),]
        model3+=[norm_layer(256),]

        model4=[nn.Conv2d(256, 512, kernel_size=3, stride=1, padding=1, bias=True),]
        model4+=[nn.ReLU(True),]
        model4+=[nn.Conv2d(512, 512, kernel_size=3, stride=1, padding=1, bias=True),]
        model4+=[nn.ReLU(True),]
        model4+=[nn.Conv2d(512, 512, kernel_size=3, stride=1, padding=1, bias=True),]
        model4+=[nn.ReLU(True),]
        model4+=[norm_layer(512),]

        model5=[nn.Conv2d(512, 512, kernel_size=3, dilation=2, stride=1, padding=2, bias=True),]
        model5+=[nn.ReLU(True),]
        model5+=[nn.Conv2d(512, 512, kernel_size=3, dilation=2, stride=1, padding=2, bias=True),]
        model5+=[nn.ReLU(True),]
        model5+=[nn.Conv2d(512, 512, kernel_size=3, dilation=2, stride=1, padding=2, bias=True),]
        model5+=[nn.ReLU(True),]
        model5+=[norm_layer(512),]

        model6=[nn.Conv2d(512, 512, kernel_size=3, dilation=2, stride=1, padding=2, bias=True),]
        model6+=[nn.ReLU(True),]
        model6+=[nn.Conv2d(512, 512, kernel_size=3, dilation=2, stride=1, padding=2, bias=True),]
        model6+=[nn.ReLU(True),]
        model6+=[nn.Conv2d(512, 512, kernel_size=3, dilation=2, stride=1, padding=2, bias=True),]
        model6+=[nn.ReLU(True),]
        model6+=[norm_layer(512),]

        model7=[nn.Conv2d(512, 512, kernel_size=3, stride=1, padding=1, bias=True),]
        model7+=[nn.ReLU(True),]
        model7+=[nn.Conv2d(512, 512, kernel_size=3, stride=1, padding=1, bias=True),]
        model7+=[nn.ReLU(True),]
        model7+=[nn.Conv2d(512, 512, kernel_size=3, stride=1, padding=1, bias=True),]
        model7+=[nn.ReLU(True),]
        model7+=[norm_layer(512),]

        model8=[nn.ConvTranspose2d(512, 256, kernel_size=4, stride=2, padding=1, bias=True),]
        model8+=[nn.ReLU(True),]
        model8+=[nn.Conv2d(256, 256, kernel_size=3, stride=1, padding=1, bias=True),]
        model8+=[nn.ReLU(True),]
        model8+=[nn.Conv2d(256, 256, kernel_size=3, stride=1, padding=1, bias=True),]
        model8+=[nn.ReLU(True),]

        model8+=[nn.Conv2d(256, 313, kernel_size=1, stride=1, padding=0, bias=True),]

        self.model1 = nn.Sequential(*model1)
        self.model2 = nn.Sequential(*model2)
        self.model3 = nn.Sequential(*model3)
        self.model4 = nn.Sequential(*model4)
        self.model5 = nn.Sequential(*model5)
        self.model6 = nn.Sequential(*model6)
        self.model7 = nn.Sequential(*model7)
        self.model8 = nn.Sequential(*model8)

        self.softmax = nn.Softmax(dim=1)
        self.model_out = nn.Conv2d(313, 2, kernel_size=1, padding=0, dilation=1, stride=1, bias=False)
        self.upsample4 = nn.Upsample(scale_factor=4, mode='bilinear')

上述模型由多个卷积层、ReLU激活函数和批归一化层组成，通过前向传播函数将输入的灰度图像（L通道）转换为彩色图像（ab通道）。如果指定了 pretrained=True，则会自动下载并加载预训练的模型权重。模型训练后，灰色图像前后对比：