No-reference quality assessment for JPEG compressed images
JPEG is a most commonly used standard of compression for digital images. Quality factor (Qfactor) for JPEG compressed image is actually a suitable indicator to the perceptual quality. However, the information of the compressor might be unknown due to various reasons. To evaluate the Qfactor, we recompress the formerly compressed image and measure the consistency between them. Then we define the fixed points (the points on the Qfactor-axis where the content of recompressed images are almost the same with that of directly compressed images) by following the Qfactor based specifications and form the image set. The quality of JPEG compressed images are measured by combining the estimated Qfactor with the features extracted from the image set. The experimental results confirm that the proposed image quality assessment technique, which is no-reference, is able to faithfully predict the visual quality of JPEG compressed images.