  Copy-move forgery is a manipulation of copying and pasting specific patches
from and to an image, with potentially illegal or unethical uses. Recent
advances in the forensic methods for copy-move forgery have shown increasing
success in detection accuracy and robustness. However, for images with high
self-similarity or strong signal corruption, the existing algorithms often
exhibit inefficient processes and unreliable results. This is mainly due to the
inherent semantic gap between low-level visual representation and high-level
semantic concept. In this paper, we present a very first study of trying to
mitigate the semantic gap problem in copy-move forgery detection, with spatial
pooling of local moment invariants for midlevel image representation. Our
detection method expands the traditional works on two aspects: 1) we introduce
the bag-of-visual-words model into this field for the first time, may meaning a
new perspective of forensic study; 2) we propose a word-to-phrase feature
description and matching pipeline, covering the spatial structure and visual
saliency information of digital images. Extensive experimental results show the
superior performance of our framework over state-of-the-art algorithms in
overcoming the related problems caused by the semantic gap.
