A method for automatically cutting sheets of pliable material, for example for shoe, leather, clothing components and the like, of the type wherein a numerical control machine, provided with an electronic control system having a memory comprising at least one reference image of the shape of the component to be cut, is designed to receive at its inlet material in the form of sheets so as to define on said sheets a processing path or point and to transfer cut portions to its outlet, said method comprising a setting step including: - storing in said memory at least one second reference image of the surface of the sheet or of the portion to be cut; - defining by means of selection, via a user interface of the electronic control system, at least one first sample portion and at least one second sample portion of said at least one second reference image, said sample portions and being opposite classification examples relating to a respective qualitative aspect of the surface of the sheet; and - obtaining a classification criterion based on said opposite classification examples provided by the first sample portion and the second sample portion of the image; said method comprising a process step including: - acquiring at least one image of the sheet to be cut, by means of image detectors associated with the machine; - classifying pixels of the acquired image of the sheet to be cut by assigning thereto a percentage value or weight according to said classification criterion, by means of an image processing unit of said electronic control system, obtaining a filtered image based on said criterion, wherein assigning to the pixels of the acquired image a percentage value or weight for obtaining a filtered image comprises assigning to each of said pixels of said acquired image a colour category; and - further processing said filtered image and the reference image of the shape of the component to be cut, so as to define the processing path or point of a cutting area of the portion of the sheet, wherein the definition of the processing path or point of the cutting area during said process step involves a comparison between said acquired image and the reference image of the shape of the portion to be cut, in order to establish and check the alignment degree of said cutting area with said reference image of the shape. said method comprising a setting step including: - storing in said memory at least one second reference image of the surface of the sheet or of the portion to be cut; - defining by means of selection, via a user interface of the electronic control system, at least one first sample portion and at least one second sample portion of said at least one second reference image, said sample portions and being opposite classification examples relating to a respective qualitative aspect of the surface of the sheet; and - obtaining a classification criterion based on said opposite classification examples provided by the first sample portion and the second sample portion of the image; - storing in said memory at least one second reference image of the surface of the sheet or of the portion to be cut; - defining by means of selection, via a user interface of the electronic control system, at least one first sample portion and at least one second sample portion of said at least one second reference image, said sample portions and being opposite classification examples relating to a respective qualitative aspect of the surface of the sheet; and - obtaining a classification criterion based on said opposite classification examples provided by the first sample portion and the second sample portion of the image; said method comprising a process step including: - acquiring at least one image of the sheet to be cut, by means of image detectors associated with the machine; - classifying pixels of the acquired image of the sheet to be cut by assigning thereto a percentage value or weight according to said classification criterion, by means of an image processing unit of said electronic control system, obtaining a filtered image based on said criterion, - acquiring at least one image of the sheet to be cut, by means of image detectors associated with the machine; - classifying pixels of the acquired image of the sheet to be cut by assigning thereto a percentage value or weight according to said classification criterion, by means of an image processing unit of said electronic control system, obtaining a filtered image based on said criterion, wherein assigning to the pixels of the acquired image a percentage value or weight for obtaining a filtered image comprises assigning to each of said pixels of said acquired image a colour category; and - further processing said filtered image and the reference image of the shape of the component to be cut, so as to define the processing path or point of a cutting area of the portion of the sheet, - further processing said filtered image and the reference image of the shape of the component to be cut, so as to define the processing path or point of a cutting area of the portion of the sheet, wherein the definition of the processing path or point of the cutting area during said process step involves a comparison between said acquired image and the reference image of the shape of the portion to be cut, in order to establish and check the alignment degree of said cutting area with said reference image of the shape.