Fig. 2

The different stages of the algorithm for post-acquisition quality evaluation of a brain MRI slice. a The test image has its (b) foreground extracted. c The test image in (a) has its pixel intensity levels rescaled to lie between 0 and 1. d Grayscale and contrast feature images are extracted from the test image. Duplicating the rescaled image in (c) extracts the grayscale image at no computational cost. e, f, g and h are the four binary feature images generated by using the first moments of the feature images in (c) and (d) as global thresholds. i Luminance contrast, texture, texture contrast, lightness and total quality scores are computed by matching relevant pairs of the feature images in (e), (f), (g) and (h)