Fruit image recognition plays an important role in the fields of smart agriculture and
digital medical [ 4 , 5]. With the rapid development of smart agriculture and digital
medical in recent years, fruit image recognition has attracted more and more
researchers’ attention. In order to meet the needs of large-scale a nd efficient fruit
recognition and classification, researchers began to identify fruit image with different
algorithms. For example, in [6], the authors proposed a fruit classification based on six
layer convolutional neural network and the classification accuracy is higher than that of
traditional single feature. In [7], the authors present an automatic fruit recognition
system for classifying and identifying fruit types and which is capable of automatically
recognize the fruit name with a high degree of accuracy. And in [8], the authors
proposed Kiwifruit recognition method at night based on fruit calyx image, whose
recognition rate reached 94.3%. And in [9], the authors propos ed a fast and accurate
object recognition method especially for fruit recognition to be used for mobile
environment. They combined color, shape, texture and intensity into their associated
code fields to generate an object code that could be used as a search key for the feature
database. And in [10], the authors given a fruit recognition method via image con-
version optimized through evolution strategy principal component analysis and
achieved a better recognition effect through the pretreatment, training and recognition
of fruit images, with an average recognition rate of over 92%.
In general, the process of fruit image recognition system mainly focuses on pre-
treatment and feature extraction. In this kind of recognition system, fruit image
acquisition is mostly conducted by placing the collected fruit in a strictly defined
background in order to ensure that the recognition system is less interfered by the
outside world, so as to improve the recognition accuracy of the system. However, the
image in the actual environment is easily affected by the factors such as illumination
change, fruit reflection and shielding, which in vary degrees impact the recognition
accuracy of fruit image. In fruit recognition system, fruit features mainly include odor,
color, shape and texture. While in the process of growth, different environment will
lead to difference in shapes, sizes and colors. In addition, natural light intensity and
shadow will also be different when frui t images are collected, which will affect the
accuracy of image recognition. What’s more, the complexity of the color and texture
features of fruit images also makes the recognition more difficult. Therefore, better
recognition algorithms are needed to solve this problem.
As a representative method in the deep learning, DBN is quite different from the
previous algorithms in terms of training method structure. By adopting the idea of
layered training, the training speed of DBN is greatly improved [11, 12]. In addition,
the idea of layering also increases the system’s ability to express complex functions.
DBN usually takes pixel-level images as input and extracts the abstract features of the
input images from bottom to top, from simple to complex, which is a process of
automatic mining useful information in the data. However, general pixel-level images
are easily affected by illumination and other factors, which affects the extraction of
essential features of input samples in DBN. In order to improve the fruit image
recognition performance of DBN under different illumination, we propose a new
method combining Census transform with DBN to extract the texture features of
images through Census transform to eliminate the influence of ununiform lighting on
the recognition results.
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