基于改进GAN的猕猴桃低光照花朵图像增强模型

    Model for enhancing low-light kiwifruit flower images based on improved GAN

    • 摘要: 针对自然条件下采集的猕猴桃花朵图像由于相互遮挡导致的图像亮度低的问题,提出一种基于改进GAN(generative adversarial network)的猕猴桃低光照花朵图像增强模型。首先,设计一种基于混合注意力的生成器,捕获低光照花朵图像亮度分布特征,强化生成器对图像亮度分布的关注。其次,引入Swin Transformer Block对图像特征进行全局建模,减少生成器在下采样过程中的特征丢失。最后,采用双判别器对生成图像进行全局和局部判别,提升生成器的细节感知力和评估精度。该方法与RetinexNet、EnlightenGAN、Zero-DEC、Cycle-GAN四种方法进行比较,在峰值信噪比(peak signal to noise ratio,PSNR)方面比EnlightenGan提高了0.11db;在NIQE(naturalness image quality evaluator)方面,比Zero-DCE降低12.41%。该方法不仅实现了低光照猕猴桃花朵图像地亮度增强,同时很好地抑制了噪声和伪影地出现,可为低光照花朵图像增强提供参考。

       

      Abstract: Uneven brightness and noise images have posed a great challenge on the recognition rate and accuracy of visual tasks, due mainly to the mutual occlusion of kiwifruit flowers in natural environments. In this article, the image enhancement was proposed to detect the kiwifruit flower under low light using improved generative adversarial network (GAN). The research object was taken as the flowers at the Meixian Kiwi Experimental Station of Northwest Agriculture and Forestry University, Shaanxi Province, China. Digital cameras and mobile phones were used to capture the images of flowers in different open states at some periods. All uniform pixel images were selected to create a dataset. Three steps were divided in the improved model of image enhancement. Firstly, GAN was used to optimize and improve the model. The channel and spatial attention were combined to perform the residual connections in the generator section. Among them, ECANet was used to more accurately extract the image features under the brightness distribution of specific areas in the channel attention. SAM was used to focus the specific regions in the image using lightweight computational operations in the spatial attention, in order to achieve the local attention. As such, the generator was obtained to extract the brightness distribution of kiwifruit low-light flower images. Secondly, a Swin Transformer block was added at the connection between the upsampling and downsampling of the generator. The Swin Transformer block was used as the standard multi-head self-attention evolution of the original Transformer. Therefore, the global modelling of the Transformer was also utilized to split the input image. The dependency relationship among each module of the image was then calculated to improve the global modelling and feature extraction of image details in the generator. Finally, the pattern collapse that encountered by single discriminators was reduced to adaptively enhance the local regions and global lighting. The generator was then provided with the required adaptive adjustment. A dual discriminator mechanism was utilized to enhance the perception of image details. The accuracy of image evaluation was improved to generate the clearer images in the generator network. On the self-built dataset, the PSNR and NIQE of the improved model were 7.09 and 10.36, respectively. Meanwhile, a comparison was then made on the five models, such as RetinexNet, Enlighten GAN, Zero DEC, Cycle GAN, and Diffusion Low Light. The peak signal-to-noise ratio of the improved model was 0.11db higher than that of EnlightenGan. The quality assessment of natural image was 12.41% lower than that of Zero DCE. Therefore, the low-light image enhancement model was performed the better quality, lower distortion, better naturalness, and smaller color deviation after enhancement. This improved model can also be applied in the practical production to develop the computer vision in smart agriculture.

       

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