concept image tensor in category deep learning

This is an excerpt from Manning's book Deep Learning with JavaScript: Neural networks in TensorFlow.js.
If the output is regarded as an image tensor (a totally valid way of looking at this!), then filters can be understood as the number of channels in the output. Unlike the input image, the channels in the output tensor don’t actually have to do with colors. Instead, they represent different visual features of the input image, learned from the training data. For example, some filters may be sensitive to straight-line boundaries between bright and dark regions at a certain orientation, while others may be sensitive to corners formed by a brown color, and so forth. More on that later.