1. A device for detecting anomalies in a digital image, called obtained image, said obtained image comprising geometrical or alphanumeric symbols, said device comprising means of storing said obtained image and a second image called anticipated image and a viewing device, the two images consisting of colored pixels referenced in a plane φ(x, y), each pixel P O (x, y) of the obtained image having three components, red, green and blue, respectively denoted P O (x, y, R), P O (x, y, G) and P O (x, y, B), and each pixel P A (x, y) of the anticipated image also having three components, red, green and blue, respectively denoted P A (x, y, R), P A (x, y, G) and P A (x, y, B), for any pixel, the sum of its three components being called luminance, the luminances being denoted P O (x, y, L) and P A (x, y, L), said device further comprising means of comparing the twe obtained image and the anticipated image, and means of generating a third image, called resultant image, each pixel P R (x, y) of the resultant image having three components, red, green and blue, respectively denoted P R (x, y, R), P R (x, y, G) and P R (x, y, B) defined as follows: if the three components of a pixel P O (x, y) of the obtained image are all identical to the three components of the pixel P A (x, y) situated in the same place in the anticipated image, then the three components of the pixel P R (x, y) are all equal and proportional to the luminance P A (x, y, L) of the corresponding pixel of the anticipated image; if at least one of the three components of a pixel P O (x, y) of the obtained image is different from the corresponding component of a pixel P A (x, y) situated in the same place in the anticipated image, then the red component P R (x, y, R) of the pixel P R (x, y) depends on the luminance P O (x, y, L) of the corresponding pixel of the obtained image, the green component P R (x, y, G) of the pixel P R (x, y) depends on the luminance P A (x, y, L) of the corresponding pixel of the anticipated image, the blue component P R (x, y, B) of the pixel P R (x, y) being zero.