Proceedings Article | 25 January 2012
Proc. SPIE. 8293, Image Quality and System Performance IX
KEYWORDS: Signal to noise ratio, Cell phones, Visualization, Imaging systems, Spatial frequencies, Cameras, Image processing, Image quality, Modulation transfer functions, Contrast sensitivity
The I3A Camera Phone Image Quality (CPIQ) initiative aims to provide a consumer-oriented
overall image quality metric for mobile phone cameras. In order to achieve this
goal, a set of subjectively correlated image quality metrics has been developed. This paper
describes the development of a specific group within this set of metrics, the spatial metrics.
Contained in this group are the edge acutance, visual noise and texture acutance metrics.
A common feature is that they are all dependent on the spatial content of the specific
scene being analyzed. Therefore, the measurement results of the metrics are weighted by
a contrast sensitivity function (CSF) and, thus, the conditions under which a particular
image is viewed must be specified. This leads to the establishment of a common framework
consisting of three components shared by all spatial metrics. First, the RGB image is transformed
to a color opponent space, separating the luminance channel from two chrominance
channels. Second, associated with this color space are three contrast sensitivity functions
for each individual opponent channel. Finally, the specific viewing conditions, comprising
both digital displays as well as printouts, are supported through two distinct MTFs.
