In Image processing, Convolutional neural network is a deep neural network that takes images as input and understands the characteristics from input data. Every colored image is divided into three layers such as red, green, and blue layers and each layer is nothing but the matrix of pixel values. The new layers are formed by mathematical operations such as convolutions and pooling on previous output. Convolutions are to extract the features and pooling to reduce the complexity of the network. The output matrix is flattened to one layer and connects it to a fully connected layer for classification.
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You can watch this video on How CNN works to know about CNN in image processing: